Spotlight on Analytical Applications Complete e-Zine Vol. 1

VOLUME 1

SPOTLIGHTON APPLICATIONS.FOR A BETTERTOMORROW.

PerkinElmer

INTRODUCTION

PerkinElmer Spotlight on Applications e-Zine – Volume 1

PerkinElmer knows that the right training, methods, applications, reporting and support are as integral to getting answers as the instrumentation. That’s why PerkinElmer has developed a novel approach to meet the challenges that today’s labs face – that approach is called EcoAnalytix™, delivering you complete solutions for your applications challenges.

In this effort, we are pleased to introduce to you our new Spotlight on Applications e-Zine, delivering a variety of topics which address the pressing issues and analysis challenges you may face in your application areas today.

Our Spotlight on Applications e-Zine consists of a broad range of applications you’ll be able to access at your convenience. Each application in the table of contents includes an embedded link which will take you directly to the appropriate page within the e-Zine.

PerkinElmer

CONTENTS

Children’s Product Safety• Determination of Formaldehyde Content in Toys using UV/Vis Spectrometry

• Determination of Hexavalent Chromium in Toys using UV/Vis Spectrometry

• UHPLC Separation and Detection of Bisphenol A in Plastics

• Lead & Other Toxic Metals in Toys Using XRF Screening and ICP-OES Quantitative Analysis

Environmental• Increased Laboratory Productivity for ICP-OES Applied to U.S. EPA Method 6010C

• Increased Sample Throughput for ICP-OES Applied to U.S. EPA Method 200.7

• Determination of Total Mercury in Soils and River Sediments using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption

• Determination of Total Mercury in Whole Blood using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption

Food & Beverage• Determination of Arsenic in Baby Foods and Fruit Juices by GFAAS

• Determination of Total Mercury in Fish and Agricultural Plant Materials using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption

• Increased Throughput and Reduced Solvent Consumption for the Determination of Isoflavones by UHPLC

• Extraction and Quantification of Limonene from Citrus Rinds using GC/MS

Semiconductor• Analysis of Impurities in Semiconductor Grade Hydrochloric Acid by Dynamic

Reaction Cell ICP-MS

• Analysis of Impurities in Ultrapure Water by Dynamic Reaction Cell ICP-MS

• Analysis of Semiconductor Grade TMAH by Dynamic Reaction Cell ICP-MS

• Analysis of Impurities in Nitric Acid by Dynamic Reaction Cell ICP-MS

Introduction

As product safety regulations for industry are becoming stricter, more testing at lower levels is required for toxic elements or hazardous organic chemicals such as formaldehyde in children’s toys/clothing. Formaldehyde resins are used in fabrics to bind pigments to the cloth, as a fire retardant and to provide stiffness. In cotton and cotton- blend fabrics they are used to enhance wrinkle resistance and water repellency. They can often be noted by the odor of treated fabric. The types of resins used include urea-formaldehyde, melamine-formaldehyde and phenol-formaldehyde. Resins without formaldehyde are typically much costlier. Increases in temperature (hot days) and increased humidity both increase the release of formaldehyde from coated textiles.

Long term chronic exposure or short-term exposure to high concentrations of formaldehyde can lead to cancer. In animal studies, rats exposed to high level of formaldehyde in air developed nose cancer. The European standard EN 71 specifies safety requirements for toys. EN 71, Part 9 contains requirements for organic chemical compounds in toys and specifies the limit for accessible textile components of toys intended for children under 3 years of age. The limit specified for formaldehyde content is not more than 30 mg/kg or 2.5 mg/L in the aqueous migrate pre-pared following EN 71, Part 10. EN 71, Part 11, section 5.5.3 specifies a method of analysis.

Children’s Products

a p p l i c a t i o n n o t e

Determination of Formaldehyde Content in Toys using UV/Vis Spectrometry

Author

Aniruddha Pisal

PerkinElmer, Inc. Shelton, CT 06484 USA

Figure 1. LAMBDA XLS+ UV/Vis spectrometer. Wavelength: 410 nm; Measurement Mode: Absorbance; Cell 10 mm.

2

The concentration of formaldehyde was found to be 1.99 mg/L.

Formaldehyde dilute standard solution (0.001 mg/mL): 2.5 mL of formaldehyde stock solution was transferred to 50-mL volumetric flask; mixed well and diluted up to the mark with water. 1 mL of this solution was further diluted to 100 mL with water and mixed well.

A series of reference solutions were prepared by pipetting suitable volumes of above formaldehyde dilute standard solution into a 50-mL conical flask as follows

Absorbance measurement of calibration solutions: Absorbance measurements of calibration reference solutions and blank were done by using water as reference. The calibra-tion curve was constructed by subtracting absorbance value of the blank solution (A2) from each of absorbances obtained from the calibration solutions. Figure 2 shows calibration graph.

Sample preparation: Three different toy samples made up with fabrics were selected for analysis. Sample with surface area of 10 cm2 was taken and transferred to 250 mL extrac-tion bottle with the help of tweezers. 100 mL of simulant (water, deionized) was added to the sample at 20 ˚C ±2 ˚C and the extraction bottle closed. The extraction bottle was kept on a magnetic stirrer for uniform stirring of the solu-tion over the period of 60 minutes. Aqueous migrate was then filtered through a plug of glass wool. 5.0 mL of aque-ous migrate was transferred into a 50-mL conical flask fol-lowed by addition of 5.0 mL of pentane-2,4-dione reagent and 20.0 mL of water.

Sample reference solution: 5.0 mL of aqueous migrate was transferred into a 50-mL conical flask followed by addition of 5.0 mL of reagent without pentane-2,4-dione and 20.0 mL of water.

These solutions were shaken for about 15 seconds and immersed in a thermostatic water bath at 60 ˚C ±2 ˚C for 10 minutes followed by cooling for about 2 minutes in a bath of iced water.

Table 2. Calibration solutions. Concentration Amounts (mL) (mg/L) of Formaldehyde Formaldehyde dilute standard Amount of after making solution in 50-mL pentane-2,4-dione volume to 30 mL conical flask reagent (mL) with water

Blank – 5.0 0.0

Reference 1 5.0 5.0 0.167

Reference 2 10.0 5.0 0.333

Reference 3 15.0 5.0 0.499

Reference 4 20.0 5.0 0.667

Reference 5 25.0 5.0 0.833

Experimental

The analysis was carried out using a PerkinElmer® LAMBDA™ XLS+ UV/Vis Spectrometer.

Apparatus and reagents

Table 1. List of apparatus and reagents used.*

Volumetric flasks, volume 50 mLVolumetric flasks, volume 100 mLHot plate for distillationBoiling chipsErlenmeyer flasks, volume 100 mLEppendorf® micropipettesAmmonium acetate, anhydrousAcetic acid, glacialPentane-2,4-dioneHydrochloric acid, 1 mol/L Sodium Hydroxide solution 1 mol/LStarch solution freshly prepared, 2 g/LFormaldehyde solution, 370 g/L to 400 g/LStandard iodine solution, 0.05 mol/LStandard sodium thiosulfate solution, 0.1 mol/LWater, deionizedStainless steel tweezers250 mL glass bottle with flat base, screw neck and PTFE lined rubber septum (Make: Schott Duran)Magnetic stirrer

*The reagents, chemicals, standards used were of ACS grade.

Pentane-2,4-dione reagent: Dissolved 15 gm of anhydrous ammonium acetate, 0.3 mL glacial acetic acid and 0.2 mL pentane-2,4-dione reagent in 25 mL water and diluted up to the mark in 100-mL volumetric flask with water.

Reagent without pentane-2,4-dione: Dissolve 15 gm of anhydrous ammonium acetate and 0.3 mL glacial acetic acid in 25 mL water and diluted up to the mark in 100-mL volumetric flask with water.

Formaldehyde stock solution: Transferred 5.0 mL of formaldehyde solution into a 1000-mL volumetric flask and made up to the mark with water.

Standardization of formaldehyde stock solution: 10.0 mL of freshly prepared formaldehyde stock solution was transferred into a conical flask, added 25.0 mL of a standard iodine solution and 10.0 mL of sodium hydroxide solution. The solution was allowed to stand for 5 minutes. Then the solution was acidified with 11.0 mL of hydrochloric acid and titrated for excess iodine by standard sodium thio-sulfate solution. 0.1 mL of starch solution was added when color of the solution became pale straw. After addition of starch solution, immediately the color was changed to deep blue-black. The titration was continued until the color changes from deep blue-black to colorless. Similarly, the blank titration was performed. The difference between titration values of blank and sample was used for calculation of formaldehyde contents in stock solution.

3

Figure 2. Calibration graph.

Figure 3. Spectrum of color formed for the determination of ‘Formaldehyde’ contents.

Absorbance measurements were done between 35 minutes and 60 minutes from the time when the conical flasks were placed in a water-bath at 60 ˚C.

Absorbance measurements of sample solutions were done by using the reference solution as reference (A1).

Calculation of analyte concentration: Calibration curve was prepared manually by taking the absorbance values obtained for calibration reference solutions. To determine the analyte concentration, absorbance value of blank solution (A2) was subtracted from absorbance value of sample solution (A1). The subtracted absorbance value was then read off from the manual calibration curve. The formaldehyde content in aqueous migrate was calculated

by using following equation,

Cs(mg/L) = C X 5 where,

Cs = concentration of formaldehyde in the sample solution (mg/L)

5 = dilution factor of the sample solution.

Results and discussion

Calibration – linearityThe six different levels of calibration standards were prepared in the range from 0.167 mg/L to 0.833 mg/L with the reagent blank as first level. Results showed linearity with a good correlation co-efficient of 0.9994. The calibration curve is shown in Figure 2. Figure 3 shows the spectrum of the developed color, confirming the peak maximum at 410 nm.

Method detection limit: 10 replicate reagent blank solutions were prepared to make an estimate of method detection limit. To determine method detection limit, seven replicate aliquots of fortified reagent water (0.1 mg/L) were prepared and processed through entire analytical method. The method detection limit was calculated as follows,

MDL = (t) X (s) where,

t = student’s t value for a 99% confidence level and a standard deviation estimate with n-1 degrees of freedom. [t = 3.143 for seven replicates].

s = standard deviation of replicate analyses.

The method detection limit was found to be 0.0178 mg/L.

For a complete listing of our global offices, visit www.perkinelmer.com/ContactUs

Copyright ©2009, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners. 008765_01

PerkinElmer, Inc. 940 Winter Street Waltham, MA 02451 USA P: (800) 762-4000 or (+1) 203-925-4602www.perkinelmer.com

Figure 4. Toy samples.

Conclusion

The LAMBDA XLS+ UV/Vis spectrometer can be used to mea-sure formaldehyde contents in fabric toys. The detection limit is sufficient to determine formaldehyde at the level of 30 mg/kg in the original material or 2.5 mg/L in the aqueous migrate solution as specified in the current version of EN-71. Linearity and spike recoveries further validate the performance of this methodology.

References

1. EN 71 Safety of Toys – Part 9, 10, 11 – organic chemical com-pounds in toys – requirements, limits and sample extraction procedure.

2. 40 CFR, Part 136 Appendix B – Definition and Procedure for the Determination of the Method Detection Limit.

Sample analysis: Three different toy samples, as shown in Figure 4, made up of polyester, rayon and synthetic fibers were analyzed as per the procedure given under ‘Experimental’. Results obtained in duplicate were averaged and are shown in Table 3. These measurements are below the action level of 2.5 mg/L in the aqueous migrate.

Table 3. Sample analysis results.

Sample Concentration (mg/L)

Toy 1 (polyester fiber) 0.18

Toy 2 (rayon fiber) 0.25

Toy 3 (synthetic fiber) Not Detected

Spike recovery studies: A recovery study was performed by spiking 0.5 mg/L concentration in three replicates of the syn-thetic fiber sample aqueous migrate. The results are summarized in Table 4. As seen in Table 4 the recoveries are good, falling within the usual acceptance range of 80-120% recovery.

Table 4. Replicate spike recoveries.

Sample % Recovery

Sample 1 113

Sample 2 107

Sample 3 105

POLYESTER RAYON SYNTHETIC FIBER

Introduction

Toy safety is a joint responsibility among governments, the toy industries, regulatory bodies and parents. The toy safety regulations are intended to reduce potential risks children could be exposed to when playing with toys. Enforcement of the regulations aims to identify those toys that do not comply with the legislation and remove them from the market. The toxic elements that may be present in toys are heavy metals such as antimony, arsenic, chromium, lead, mercury, etc., which can accumulate in the body and may cause adverse effects. Therefore,

analysis of such elements is important to ensure safety. The European standard EN 71 specifies safety requirements for toys. EN 71, Part 3 contains one section entitled “Migration of certain elements”. In this section it defines the limits for element migration from toy materials including hexavalent chromium. In EN 71, Part 3, the limit specified for migration of chromium is not more than 60 mg/kg. In the environment, chromium is found in several different forms including two oxidation states as trivalent i.e., Cr(III) and hexavalent i.e., Cr(VI). Cr(III) is considered to be an essential nutrient for the body. In contrast Cr(VI) is relatively mobile in the environment and is acutely toxic and carcinogenic. It is widely used in electroplating, stainless steel production, leather tanning, paint, and textile manufacturing.

During the analysis, sample preparation was carried out using European method EN 71, Part 3, specifying extraction of sample by hydrochloric acid for 2 hours at 37 ˚C in darkness followed by colorimetric determination of hexavalent chromium by 1,5-diphenylcarbazide reagent.

Children’s Products


Determination of Hexavalent Chromium in Toys by using UV/Vis Spectrometry

Figure 1. LAMBDA XLS+ UV/Vis spectrometer. Wavelength: 540 nm; Measurement Mode: Absorbance; Cell 10 mm.

Author

Aniruddha Pisal


2

Absorbance measurement of calibration solutions: Background correction was performed with blank solution and absorbance of calibration reference solutions were measured at 540 nm using 10 mm cell. Figure 2 shows the calibration graph.

Sample analysis: Different toy samples selected for analysis were, ‘yellow plastic’; ‘green fabric’ and ‘toy coated with paint’. 100 mg of test portion of sample was taken and cut into small pieces. For toy sample with paint coating, the coating layer was scraped off for analysis. The test portion so prepared was mixed for about 1 minute with 5 mL of 0.1 mol/L hydrochloric acid at 37 ˚C ±2 ˚C. pH of the solution was adjusted to between 1 and 1.5 with 2 mol/L hydrochloric acid. The mixture was protected from light, kept at 37 ˚C ±2 ˚C and agitated for 1 hour continuously and then allowed to stand for 1 hour at 37 ˚C ±2 ˚C. Then the solution was filtered immediately through a membrane filter and diluted to about 90 mL with distilled water. The pH of the solution was adjusted to 2.0 ±0.5 using phosphoric acid and 0.2 N sulfuric acid. The solution was transferred to a 100-mL volu-metric flask and diluted up to the mark with distilled water. 2 mL of diphenylcarbazide solution was added to the solution and allowed to stand 10 minutes for full color development. An appropriate portion was transferred to a 1 cm absorption cell and measured the absorbance at 540 nm with the blank as a reference.

Results and discussion

Calibration – linearityThe seven different levels of calibration standards were prepared in the range from 0.1 mg/L to 1.0 mg/L with reagent blank as first level. Results showed linearity with a good correlation co-efficient of 0.9997. The calibration curve is shown in Figure 2.

Spike recovery studies: A recovery study was performed at 0.5 mg/L concentration in three replicates. The results are summarized in Table 3. As seen in table, the recoveries are good, approximately 105 percent. This demonstrates that the extraction is not causing transformation of the Cr(VI) spike to Cr(III).

Table 2. Calibration solutions.

Amount of chromium standard solution Concentration (5 mg/L) in 100 mL (mg/L)

Blank – 0

Reference 1 2 mL 0.10






Experimental

The analysis was carried out using PerkinElmer® LAMBDA™ XLS+ UV/Vis spectrometer as shown in Figure 1.

Apparatus and reagents

Table 1. List of apparatus and reagents used.

pH meterVolumetric flasks, volume 100 mLErlenmeyer flasks, volume 250 mLWater bath Boiling chipsEppendorf® micropipettesSodium hydroxide, 1NPotassium dichromate, dried Nitric acid, concentratedSulfuric acid, concentratedSulfuric acid, 0.2 NPhosphoric acid, concentratedHydrochloric acid, 0.1 M1,5 DiphenylcarbazideAcetone

*The reagents, chemicals, standards used were of ACS grade.

Chromium stock solution (500 mg/L): Dissolved 141.4 mg of potassium dichromate in water and diluted to 100 mL.

Chromium standard solution (5 mg/L): Diluted 1.0 mL of above chromium stock solution to 100 mL.

Diphenylcarbazide solution: Dissolved 250 mg of 1,5-diphenylcarbazide in 50 mL acetone and stored in brown bottle.

Series of reference solutions were prepared by pipetting suitable volumes of above chromium standard solution, as shown in Table 2, into 100-mL volumetric flasks.

3

Figure 2. Calibration graph.

Table 3. Replicate spike recoveries.

Sample % Recovery

Sample 1 104.8

Sample 2 104.6

Sample 3 104.6

Method detection limit: 10 replicate reagent blank solutions were prepared to make an estimate of method detection limit. To determine method detection limit, seven replicate aliquots of fortified reagent water (0.01 mg/L) were pre-pared and processed through entire analytical method. The method detection limit was calculated as follows,

MDL = (t) X (s) where,

t = student’s t value for a 99% confidence level and a standard deviation estimate with n-1 degrees of freedom. [t = 3.143 for seven replicates].

s = standard deviation of replicate analyses.

The method detection limit found to be 0.003 mg/L.

Sample analysis: Results obtained for different toy samples are presented in Table 4. The yellow paint exceeds the limit specified in the current standard for total chromium (60 mg/Kg). The anticipated revision to the EU standard recommends a limit of 0.02 mg/Kg hexavalent chromium in a dry, brittle or pliable toy, much lower than the current standard and based on the species. The detection limit measured here is sufficient for the new regulatory level if a larger sample is taken for extraction or a smaller dilution is used.

Table 4. Sample analysis results (calculations are based on total amount extracted and dilution factor).

Sample Cr +6 – Total Chromium –

UV result (mg/Kg) ICP result (mg/Kg)

Yellow Plastic 5.4 29.9

Green Fabric ND 2.6

Blue Paint-1 7.2 89.5

Blue Paint-2 11 66.9

Yellow Paint-1 430 1790

Yellow Paint-2 360 1870

Red Paint-1 ND 58.4

Red Paint-2 ND 47.4

*ND: not detected

The total amount of chromium in the extracts was measured using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) with resulting values in Table 4. Since the total chromium value is made up of both Cr(III) and Cr(VI) this is a good indication of the maximum amount of Cr(VI) that might be present. This provides an order-of-magnitude confirmation of the analysis.

Yellow PlasticGReeN FaBRicPaiNt-coateD toY

Figure 3. Toy samples.

Conclusion

The LAMBDA XLS+ UV/Vis spectrometer can be used to measure Cr(VI) contents in toys. The detection limit is sufficient to determine Cr(VI) at low levels and can be improved by taking a larger sample for extraction and reducing the dilution factor if the new revisions to EN 71 require it. Linearity and spike recoveries further validate the performance of this methodology.

The sample extraction used here may not be representative of the extraction that may be recommended in the final revision of EN 71 specifically for Cr(VI), but represents a reasonable approach to demonstrate the resulting analysis.

Overall, the capability to measure Cr(VI) using the UV/Vis procedure with the LAMBDA XLS+ has been successfully demonstrated.

References

1. Standard Methods for the Examination of Water and Wastewater”, Method 3500-Cr, American Public Health Association.

2. EN 71-3:1995 Safety of Toys – Part 3 Migration of certain elements.

3. 40 CFR, Part-136 Appendix B – Definition and Procedure for the Determination of the Method Detection Limit.




A P P L I C A T I O N N O T e

Liquid Chromatography

Introduction

The BPA or bisphenol A (Figure 1) has become well know over the past year as concerns for its effect on human health and well being have been raised. The concerns over BPA began with baby bottles and spread to include other types of bottles.

BPA is used in the production of two very common polymers PVC and Polycarbonate. PVC, Polyvinyl chloride, is used in many different products including building materials, medical devices and children’s toys. BPA is used in PVC production as a polymerization inhibitor, residual BPA may remain after the polymerization is complete. Polycarbonate is another very commonly used plastic. It has very desirable properties for both optical clarity and heat resistance. BPA is an important monomer in the production of polycarbonate polymer, not all of the BPA is consumed in the pro-duction and may leach out of the polymer. Recently, many applications of polycarbonate have been replaced with new copolymers, such as co-polyester, to eliminate BPA.

Author

Roberto Troiano, PerkinElmer

William Goodman, PerkinElmer

Figure 1: Structure of Bisphenol A (BPA).

UHPLC seParation and deteCtion of BisPHenoL a (BPa)in PLastiCs

2

As a result of the health concerns over human exposure to BPA this molecule is now monitored in specific products, including baby bottles and other children’s products. Simple and robust test methods are needed to determine the presence and amount of BPA in plastic materials. This paper will present the extraction and HPLC analysis of children’s products for BPA.

Experimental

The study presented here includes extraction of BPA from a toy matrix and analysis with UHPLC. The extraction procedure used here is intended to simulate the contact routes through which children are likely to encounter BPA. Two different extrac-tion techniques were used to analyze BPA in samples (30 g sam-ple used for each extraction). The first extraction method immersed the sample in 1 L of water, at 40 ˚C for 24 hours (EN 14372). The second immersed the sample with 1 L HCl (0.07 M) at 37 ˚C for 2 hours. Following extraction the samples were ana-lyzed with a PerkinElmer Flexar™ FX-10 UHPLC system includ-ing a PerkinElmer Series 200a Fluorescence detector. The sepa-ration was performed on a Brownlee Validated C8 Column (see Table 1).

Figure 2: Children's toy samples analyzed for BPA in this application note.

Table 1: HPLC Conditions for the Analysis of BPA

HPLC System PerkinElmer Flexar FX-10 UHPLC

Injection Volume 50 μL

Column PerkinElmer C8 (150 mm x 4.6 mm, 5 μm)

Mobil Phase Methanol/Water (65/35)

Flow Rate 1 mL/min

Detector Wavelength Excitation – 275 nm / Emission – 313 nm

Detector Response Time 0.1 sec

PMT, Em BDW Super High, Wide

Run Time 15 min

Concentration Response

1 ppb 54163

10 ppb 378051

20 ppb 820335

40 ppb 1548750

50 ppb 1957851

0.9993

Table 2: Table for the analysis of BPA across the range of 1 – 50 ppb (µg/L).

Results

The BPA analyzed with the given LC conditions eluted at 5.43 mins (Figure 3). The UHPLC system was calibrated across a range of 1 – 50 ppb (µg/L) BPA (Table 2).

Sample Extraction Type µg/L µg/g

Cube water 2.04 0.068

Cube HCl ND ND

Die water 3.35 0.111

Die HCl 1.56 0.052

Dwarf water 4.32 0.144

Dwarf HCl 1.78 0.059

Table 3: Results from toy sample analysis.

Figure 3: BPA calibration standard at 1 ppb.

The limit of quantitation (LOQ) for BPA with the method pre-sented here is 1 ppb. The signal to noise at the LOQ is approxi-mately 10:1. The response across the calibration range fit a linear calibration with an r2 value of 0.9993. Blanks analyzed between standards and samples showed the system was free from any BPA contamination or carryover.

BPA in the extracts of the toy samples were quantified using the calibration curve generated during standard analysis (Table 3). Figure 4 shows the chromatogram of the water extract of the toy dwarf sample.

r2


Copyright ©2009, Perkinelmer, inc. all rights reserved. Perkinelmer® is a registered trademark of Perkinelmer, inc. all other trademarks are the property of their respective owners. 008731_01 Printed in Usa

PerkinElmer, Inc.940 Winter street Waltham, Ma 02451 Usa P: (800) 762-4000 or (+1) 203-925-4602www.perkinelmer.com

The extraction procedure which heated the toy for 24 hours in water at 40 ˚C extracted a significantly higher amount of BPA from the matrix than the extraction in acid. BPA was found in all three water extractions within the calibration range of the stan-dard curve.

Conclusion

As health concerns over exposure to BPA are raised, its analysis in plastics is becoming very important. The PerkinElmer Flexar FX-10 UHPLC system provides a sensitive and robust platform for this analysis. Demonstrated here was a calibration of BPA across a range of 1 – 50 ppb with a chromatographic run time of less than 10 minutes. This analysis was applied to 3 toy samples and BPA was identified in each sample.

Figure 4: Analysis of toy dwarf for BPA using water.

Introduction

From 2007 to 2008, the number of recalls for toys exceed-ing the U.S. limits set for lead dropped 43%. This represents however, more than 300,000 individual products posing potential hazardous exposure for children. The Consumer Product Safety Improvement Act of 2008 (CPSIA 2008) defines a children’s product as a product primarily used by a child under the age of 12 and defines new levels of lead allowed in those products1. Allowable lead in painted surfaces will be reduced from 600 mg/kg to 90 mg/kg one year from enactment of the legislation (enactment date:

August 14, 2008). Allowable total lead content (surface and substrate) is reduced from 600 mg/kg to 100 mg/kg, incrementally over the course of three years. The American Academy of Pediatrics suggests that a level close to the background level in soil of 40 mg/kg would be most protective of children’s health2.

Currently, EN-71, Part 3 and ASTM 963 specify evaluation of the toy by soaking in a mild hydrochloric acid solution at body temperature and measuring the accessible metal extracted into the solution. If a coating can be separated, a total analysis of the coating to comply with lead content requirements can be done. CPSIA 2008 provides no exemption for electroplated substrates, so that a total analysis on both coating and substrate must be done, though little other measurement guidance is currently available. EN-71 may also be revised in the near future to add other hazard-ous elements, such as aluminum, cobalt, copper, nickel, and others. The evolving need to measure lead and other metals at increasingly lower levels makes information on analysis technologies and performance valuable in making knowledgeable decisions.

Children's Products

a p p l I c a t I o n n o t e

authors

Zoe Grosser, ph.D. laura thompson lee Davidowski, ph.D. PerkinElmer Inc. Shelton, CT

Suzanne Moller Innov-X Systems Woburn, MA

Lead and Other Toxic Metals in Toys Using XRF Screening and ICP-OES Quantitative Analysis

2

A variety of techniques can be used to meet the regula-tions, including atomic absorption (both flame FLAA and graphite furnace GFAA), inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). Hand-held energy dispersive XRF, requiring minimal or no sample preparation can provide a way to screen products on-site as to determine whether further quantitative analysis is required.

The techniques are compared for several parameters in Table 1.

Since the techniques in Table 1 have different character-istics, which would be the most suitable for the variety

of children’s products, including toys that may require analysis? This question is addressed in this work using ICP-OES and hand-held XRF to examine a variety of toy materials. Ease of use and agreement between techniques at the current level for lead were evaluated.

experimental

A variety of children’s toys were obtained randomly from a church nursery room and other sources. One known recalled item, Boy Scout totem badges of differing ages were also obtained. Figure 1 shows the variety of toys, including fabric, soft and hard toys and some with painted surfaces.

Table 1. Comparison of Several Analysis Techniques for Lead Determination (mg/kg).

GFAA ICP-OES ICP-MS Hand-held XRF

Estimated detection limit for lead* 0.025 0.5 0.025 NA**

Sample prep required Yes Yes Yes No

Simultaneous multielement No Yes Yes Yes

* Includes a 500x dilution to account for sample preparation for GFAA, ICP-OES, and ICP-MS. Detection limits can be further improved if a smaller dilution is used.**NA: screening tool, detection limits matrix driven.

Table 2. Microwave Digestion Program.

Power (W) Ramp (min) Hold (min) Fan

500 5:00 15:00 1

900 10:00 15:00 1

0 20:00 2

Table 3. ICP-OES Instrumental Conditions.

Instrument Optima 7300 DV ICP-OES

RF Power 1450 W

Nebulizer Flow 0.55 L/min

Auxiliary Flow 0.2 L/min

Plasma Flow 15.0 L/min

Sample Pump Flow 1.2 mL/min

Plasma Viewing Axial

Processing Mode Area

Auto Integration 5 sec min-20 sec max

Read Delay 30 sec

Rinse 30 sec

Replicates 3

Background Correction one or two points

Spray Chamber Cyclonic

Nebulizer SeaSpray (Glass Expansion®, Pocasset, MA)

Figure 1. Variety of toys measured.

Figure 2. XRF result screen.

elements over a wide dynamic concentration range, from ppm levels up to virtually 100% by weight. An example of the result obtained on the screen is shown in Figure 2.

Results and Discussion

The analysis of the toys by hand-held XRF and ICP-OES are shown in Table 4. The check mark in the XRF column indicates the XRF analysis displayed a lead value higher than the limit of 600 mg/kg in the screened toy indicating further quantitative analysis is recommended. The value determined by ICP-OES confirms that the value was higher than the regulatory limit in the coating or for a total analysis of the substrate material. In this case, the value measured with XRF is not reported although the value would give further refinement of the concentration for the elements measured.

Detection limits for the ICP-OES are shown in Table 5 for both the digested solution and the amount in the origi-nal material. Since the amount taken for digestion may vary and the dilution can be changed, a 500x dilution was assumed for the calculation. This represents a typical 0.1 g of material diluted to a final volume of 50 mL.

Duplicate sample preparation and analysis of several samples can indicate the reproducibility of the method, provided the samples are homogeneous. Table 6 shows the results for duplicate sample preparation and analysis of three different types of samples. The fabric and the uniformly-colored plastic show good agreement between the duplicate analyses (less than 20% relative percent difference). The puzzle board required scraping paint from the surface for analysis and it was difficult to uni-formly remove only the paint without taking some of the substrate, as shown in Figure 3. This may contribute to the very different values obtained for the duplicate analysis.

Samples were prepared for ICP-OES analysis by scraping off the paint or cutting the substrate into small pieces. Approximately 0.01-0.1 g was weighed into a Teflon® microwave digestion vessel and 6 mL of concentrated nitric acid (GFS Chemical®, Columbus, Ohio) and 1 mL of concentrated hydrochloric acid (GFS Chemical®, Columbus, Ohio) were added. The samples were placed in the Multiwave™ 3000 microwave digestion system (PerkinElmer, Shelton, Connecticut) and digested according to the program shown in Table 2.

The Optima™ 7300 DV was used for analysis of the full suite of elements currently regulated in EN-71, Part 33 and referenced in ASTM D9634, and CPSIA, including lead. The conditions are as shown in Table 3.

The Innov-X® Import Guard model was used for all hand-held XRF measurements, and a general calibration was performed. For analysis of the same samples with XRF, no sample preparation was required. The system uses energy dispersive X-ray fluorescence and easily identifies

3

Figure 3. Puzzle board and scrapings.

Table 4. Results for Toys Measured with XRF and ICP-OES (mg/kg). XRF Antimony Arsenic Barium Cadmium Chromium Lead Mercury Selenium

Toy Stove Knob √ 32 <DL 2 4 773 3950 <DL 13

Yellow Mega Block √ 12 <DL 56 3 774 3690 <DL 27

Badge-1 New (Yellow Paint) √ <DL <DL 16900 14 7340 34500 <DL 85

Badge-2 Older (Yellow Paint) √ <DL <DL 21200 2 8870 42100 <DL 20

Yellow Baby Rattle √ <DL <DL 70 <DL 544 2970 <DL 8

Yellow Crib Toy Holder Strap √ 15 <DL 146 <DL 377 1900 <DL <DL

Green Cup <DL <DL 3220 2260 4 17 <DL 6

Red Ring <DL <DL 91 4 3 15 <DL 8

Table 8 shows an example for a hydrochloric acid extract from a toy, extracted and measured using procedures specified in EN-71, Part 3. Both the original set of ele-ments reported and the elements determined later (in blue) by reprocessing the data to examine the informa-tion previously stored for those elements are listed. This can be useful in assessing samples that may have been dis-posed or in better understanding the scope of samples in preparing for future analyses.

A more extensive analysis of reproducibility is shown in Table 7. The standard deviation of five separate digestions and analyses for a yellow ball (Figure 4) show excellent precision.

It is interesting to note the lead level is high, in agreement with the XRF analysis. Several other elements, such as chromium, are also high. The XRF value reported for lead in the ball was 3940 mg/kg.

Regulations are continually changing and may require different elements to be monitored in the future, at dif-ferent concentration levels. One way to help in preparing for that eventuality is the use of the universal data acqui-sition (UDA) feature, exclusive to the Optima ICP-OES software. In this case the Optima ICP-OES collects data for all of the wavelengths all of the time. If a standard is run at the time of the original data acquisition that includes more elements than the elements of interest at that moment, other elements can be measured with good quantitative accuracy by reprocessing at a later date. If an elemental concentration is of interest for an element that was not included in any of the usual multi-element standards, reprocessing can provide a semiquan-titative result, usually within ±30% of the true value.

4

Table 5. Estimated Detection Limits.

Element Detection Limit Detection Limit in Solution (mg/L) in Solid (mg/kg)

Antimony (271 nm) 0.008 3.8

Arsenic (189 nm) 0.002 1.2

Barium (233 nm) 0.004 1.9

Cadmium (228 nm) 0.002 1.1

Chromium (267 nm) 0.003 1.6

Lead (220 nm) 0.010 6.4

Mercury (254 nm) 0.005 2.2

Selenium (196 nm) 0.011 5.7

Table 6. Duplicate Sample Preparation and Analysis (mg/kg). Antimony Arsenic Barium Cadmium Chromium Lead Mercury Selenium

Green Fabric 15 <DL 302 <DL 332 1780 <DL <DL

Green Fabric -Duplicate 13 <DL 329 <DL 362 1940 <DL <DL

Puzzle Board 919 <DL 14 4 21,200 121,000 <DL 49

Puzzle Board - Duplicate 2187 <DL 5 5 14,600 82,600 <DL 15

Yellow Handle <DL <DL 360 <DL 1310 4990 <DL <DL

Yellow Handle - Duplicate <DL <DL 336 <DL 1200 4620 <DL 12

Table 7. Analysis of Five Replicate Samples of a Yellow Ball.

Element Average (mg/kg) SD

Antimony (271 nm) 10.6 0.49

Arsenic (189 nm) 12.4 1.8

Barium (233 nm) 707 3.1

Cadmium (228 nm) 78.3 0.73

Chromium (267 nm) 414 2.3

Lead (220 nm) 1980 9.7

Selenium (196 nm) 16.3 1.3

Mercury (254 nm) <DL –

Figure 4. Yellow ball measured in replicate.

For a complete listing of our global offices, visit www.perkinelmer.com/contactUs


perkinelmer, Inc. 940 Winter Street Waltham, MA 02451 USA P: (800) 762-4000 or (+1) 203-925-4602www.perkinelmer.com

conclusion

The regulatory landscape of toy measurements for hazard-ous metals is changing and will continue to change as ele-ments, concentrations, and sample preparation procedures are refined and harmonized between the U.S. and Europe. Indeed, the lowest limits of 90 and 100 ppm are designated as what the CPSC deems to be feasible at the time and lower limits may be regulated in the future.

ICP-OES is the accepted certifying tool in determining a wide variety of metals that may contaminate toys, either in the substrate or a paint coating. Lead can be determined at the current 600 mg/kg concentration level permitted and the ICP-OES has sufficient detection capability that the new limits of 90 mg/kg can be reliably detected.

ICP-OES and XRF are complementary techniques that work well together at the current regulatory level of 600 mg/kg. XRF provides rapid screening with a high degree of confi-dence when the sample is contaminated with lead. Highly accurate ICP analyses can be efficiently directed to the samples most likely contaminated using hand-held XRF’s quick screening and no-sample prep characteristics.Samples identified as contaminated can be prepared and analyzed by ICP with less wasted time on uncontaminated samples, because of the positive screening result. As the limits are lowered, XRF will continue to perform as a screening technique, with ICP-OES providing confirmation with regulatory requirements.

References

1. Consumer Product Safety Improvement Act, http://www.cpsc.gov/ABOUT/Cpsia/legislation.html

2. Testimony of Dana Best, MD, MPH, FAAP on behalf of the American Academy of Pediatrics, http://www.aap.org/visit/coeh/COEH Ltr 2007-09-20 Lead Testimony.pdf

3. EN-71, Part 3 The Safety of Toys, Migration of Certain Elements, may be purchased from http://www.standardsuk.com/shop/products_view.php?prod=26164

4. ASTM D-963-07, Standard Consumer Safety Specification for Toy Safety, may be purchased from http://www.astm.org

Table 8. Universal Data Acquisition for Additional Elemental Data.

Element mg/kg extracted from solid

Antimony (271 nm) 6.7

Arsenic (189 nm) 1.5

Barium (233 nm) 1850

Cadmium (228 nm) < DL

Chromium (267 nm) 655

Lead (220 nm) 2900

Selenium (196 nm) < DL

Aluminum (396 nm) 438

Cobalt (228 nm) < DL

Copper (327 nm) < DL

Manganese (257 nm) < DL

Nickel (231 nm) < DL

Tin (189 nm) < DL

Zinc (206 nm) 1230

Abstract

The use of an ESI SC FAST autosampler coupled to a Perkin Elmer Optima 7300 DV ICP can dramatically improve produc-tivity for the analysis of environmental samples using EPA SW-846 Method 6010C. Sample throughput, as determined by sample-to-sample run time can be improved by as much as 100% as compared

to traditional sample introduction systems and autosampler configurations. Both sample analysis time and rinse out time are significantly reduced, allowing for a doubling of overall productivity. In addition, stability of the plasma and instrument is very robust allowing for long, unattended run times while meeting calibration and method QC requirements. Valuable man hours spent on instrument maintenance and recalibration are reduced. This paper will demonstrate that these productivity enhancement claims can be accomplished for implementation SW-846 Method 6010C.

ICP-OES


Authors

Paul Krampitz

Stan Smith


Increased Laboratory Productivity for ICP-OES Applied to U.S. EPA Method 6010C

2

The analytical test methods found in SW-846 are commonly used by laboratories for the analysis of a wide range of sample matrices including, but not limited to: groundwater, surface water, leachates, soils, and a whole host of other solid and liquid wastes, both organic and aqueous. The RCRA regulatory programs for which SW-846 is most commonly used can be found in the U.S. Code of Federal Regulations (CFR), specifically Title 40 CFR Parts 122-270. One of the methods found in SW-846 that is commonly used by most environmental labora-tories for the analyses of elements in environmental samples is 6010C Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES).

Method 6010C is the fourth version of this method and was released as part of SW-846 Update IV in February, 2007. As indicated in the method, all samples other than filtered, pre-served groundwaters require acid digestion prior to analysis. There are more than 8 acid digestion methods applicable to ICP-AES found in SW-846 and some of those that are commonly used for the preparation of environmental samples include:

• 3005AAcidDigestionofWatersforTotalRecoverableorDissolved Metals for Analysis by FLAA or ICP Spectroscopy

• 3010AAcidDigestionofAqueousSamplesandExtractsfor Total Metals for Analysis by FLAA or ICP Spectroscopy

• 3015AMicrowaveAssistedAcidDigestionofAqueousSamplesandExtracts

• 3050BAcidDigestionofSediments,Sludges,andSoils

• 3051AMicrowaveAssistedAcidDigestionofSediments,Sludges, Soils, and Oils

Summary of Method

Method 6010C is a general analytical method that is applicable to a wide variety of liquid and solid samples and that provides specific procedures and references for sample collection, preservation, and preparation (i.e., acid digestion), in addition to recommended instrument procedures for calibration, detection limits, and interference correction. In addition, SW-846 6010C also contains procedures for the preparation, analysis, and acceptance limits for quality control samples needed for each batch of samples to be analyzed. While the method is intended only as a guidance document and is subject to interpretation and modification, implementation of the QC criteria as stated in the method was followed for the work performed and summarized in this paper. The EPA has approved this method for the analysis of 31 elements and Table I includes all the elements analyzed and their associated wavelengths. Following is a summary of the procedure from SW-846 6010C as performed in this work.

Introduction

Since 1980, the EPA has maintained a publication entitled SW-846 Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, more commonly referred to simply as SW-846. Currently, SW-846 is in its third edition and includes several updates. Since the third edition was released in 1986, there have been 9 updates (Updates I, II, IIA, IIB, III, IIIA, IIIB, IVA, and IVB), the most recent of which was dated February, 2007. Included in SW-846 are over 200 documents related to quality control practices, analytical test methods, sampling methods, and other topics related to the United States Environmental Protection Agency (EPA) Resource Conservation and Recovery Act (RCRA). Essentially, SW-846 is the official compendium of analytical and sam-pling methods that have been evaluated and approved by the EPA for use in complying with RCRA regulations.

As indicated by the EPA, the analytical methods in SW-846 are intended to be guidance documents and are not intended tobeoverlyprescriptiveexceptinthecaseswhereaparticular analyte or parameter is considered method defined. Such method-defined parameters are where the analytical result is wholly dependent on the process and conditions of the test or preparationmethodsuchastheToxicityCharacteristicLeachingProcedure (TCLP), Method 1311, where the conditions specified in the method directly affect the concentration of analytes extractedintotheleachingsolution.However,despitethisclearindication from the EPA that SW-846 methods are intended as guidance documents, many regulatory agencies invoke these methods with no permissible changes or modifications.

Figure 1. Schematic of FAST sample introduction system coupled to an Optima 7300 DV ICP spectrometer.

3

Summary of Method 6010C

Establish Initial Demonstration of Performance

1. Perform Instrument Detection Limits (IDL)

2. Determine Linear Dynamic Range (LDR)

a. Recovery of elements must be ±10% of the known values for each element

3. Determine whether interelement corrections are needed by

analysis of an Interference Check Solution (ICS)

Routine Analysis

1. Light plasma and warm up instrument, allow 15-30minutes

2. Optimize instrument and plasma conditions per instrument manufacturer

3. Calibrate ICP using blank and minimum of one standard

a. Rinse with blank between each standard

b. Use the average of multiple readings (3 replicates in this study) for all standards and samples

4. Verify calibration by analyzing the Initial Calibration Verification (ICV) standard

a. ICV standard must be from a separate source as used for calibration standards

b. Recovery of elements must be ±10% of the known values for each element

5. VerifythelowestquantificationlimitbyanalyzingtheLowerLimit of Quantitation Check Sample (LLQC)

a. LLQC standard should be from the same source as the calibration standards


6. Analyze the Initial Calibration Blank (ICB)

a. Target elements should not be detected at or above the Lower Limit of Quantitation

7. Analyze test samples along with appropriate batch quality control samples

8. After every 10 samples, verify calibration by analyzing the Continuing Calibration Verification (CCV) standard

a. CCV standard should be from the same source as the calibration standards


9. Immediately following the analysis of each CCV, analyze the Continuing Calibration Blank (CCB)

a. Target elements should not be detected at or above the Lower Limit of Quantitation

10. The LLCCV must be analyzed at the end of each analytical batch but is also recommended to be analyzed after every 10 samples

a. Recovery of elements must be ±30% of the known values for each element

11. At the end of the run, analyze the CCV and CCB

a. Acceptance limits are the same as in steps 8 and 9

Table I. Wavelengths Monitored and Viewing Modes Used for

SW-846 6010C.

Wavelength

Analyte Symbol Monitored (nm) View

Aluminum Al 308.215 Radial

Antimony Sb 206.836 Axial

Arsenic As 188.979 Axial

Barium Ba 233.527 Axial

Beryllium Be 234.861 Radial

Boron B 249.677 Radial

Cadmium Cd 226.502 Axial

Calcium Ca 315.887 Radial

Chromium Cr 267.716 Axial

Cobalt Co 228.616 Axial

Copper Cu 327.393 Axial

Iron Fe 238.204 Radial

Lead Pb 220.353 Axial

Lithium Li 670.784 Radial

Magnesium Mg 285.213 Radial

Manganese Mn 257.610 Axial

Molybdenum Mo 202.035 Axial

Nickel Ni 231.604 Axial

Phosphorus P 213.617 Axial

Potassium K 766.490 Radial

Selenium Se 196.026 Axial

Silicon Si 251.611 Radial

Silver Ag 328.068 Axial

Sodium Na 589.592 Radial

Strontium Sr 407.771 Radial

Thallium Tl 190.801 Axial

Tin Sn 189.927 Axial

Titanium Ti 334.940 Axial

Vanadium V 292.402 Axial

Zinc Zn 206.200 Axial

Internal Standards

Yttrium Y 371.029 Radial/Axial

Tellurium Te 214.281 Radial/Axial

Initial Performance Demonstration

Instrument Detection Limits

The Instrument Detection Limits (IDL) for all elements were determined using a reagent blank solution according the procedures in Section 9.3 of SW-846 6010C. Specifically, a reagent blank was analyzed seven consecutive times, with routine rinsing procedures between each analysis, for all ele-ments three times on non-consecutive days. The IDLs were then estimated by calculating the average of each element’s standard deviation. The obtained IDLs are presented in Table III.

Evaluation of Interferences

Interferences were evaluated according to Section 4.2.10 of Method 6010C. An interference check solution containing 500mg/LofAl,Ca,Mg,Na,200mg/LofFeand50mg/LofK was used for evaluation.

Batch Quality Control Samples

1. Analyze the Method Blank

a. Target elements should not be detected at or above 10% of the Lower Limit of Quantitation

2. Analyze the Laboratory Control Sample (LCS)

a. Recovery of elements must be ±20% of the spiked values for each element

3. AnalyzetheMatrixSpike

a. Recoveryofelementsmustbe±25%ofthespiked values for each element

4. AnalyzetheSampleDuplicateorMatrixSpikeDuplicate

a. The precision criterion for duplicates is a relative percent difference of no greater than 20%

Experimental

Instrument

An Optima 7300 DV (PerkinElmer, Shelton, CT) was used in conjunction with an SC-FAST (Elemental Scientific Inc., Omaha,NE)fortheanalysisofallsamplesdescribedinthiswork. The FAST sample introduction system is controlled through the Optima WinLab32™ software and a schematic of the FAST is shown in Figure 1. The elements, wavelengths, and plasma viewing modes used are listed in Table I. The instrument conditions for both the Optima ICP-OES and the SC-FASTaswellastheexperimentalparametersusedare provided in Table II.

Standards

All calibration standards and non-sample solutions were prepared with ASTM Type I (i.e., >18MΩ-cm) deionized water and trace metals grade or better nitric acid.

Internal Standards

Allsampleswerespikedwith1.5mg/Lofyttriumand2.5mg/Lof tellurium. The spiking solution was made from 1000 mg/L single element stock solutions.

Calibration

The calibration blank and standards were prepared in 1% nitric acid. Calibration was performed using a calibration blank and a single standard containing all elements at 1 mg/L. The calibration standard was prepared from a combination of single element and multi-element stock solutions, all containing elements at 1000 mg/L.

Monitored Wavelengths

As previously mentioned, the monitored elements, wavelengths, and plasma viewing modes used are listed in Table I.

4

Table II. FAST-Optima 7300 DV Instrumental Conditions and

Experimental Parameters.

Optima 7300 DV Parameters

RF Power 1450 watts

Plasma Gas Flow 15 L/min

Auxiliary Gas Flow 0.2 L/min

Nebulizer Gas Flow 0.6 L/min

Peristaltic Pump Speed 0.85 mL/min

Nebulizer/Spray Chamber Sea Spray/Glass cyclonic

Torch Cassette Position -3

Purge Normal

Resolution Normal

Integration Time 2 s min/5 s max

Read Delay 14 s

Wash Time 1 s

Number of Replicates 3

FAST Parameters

Sample Loop Volume 2 mL

Sample Loop Fill Rate 27 mL/min

Carrier Pump Tubing Black/Black (0.76 mm i.d.)

Sample Load Time 7 s

Rinse 1 s

Analysis Time (total) 75 s (sample-to-sample)

Experimental Parameters

Carrier Solution 1% HNO3 plus 0.05% surfactant

Rinse Solution 1% HNO3

Acidity of Stds/Samples 1% HNO3

Linear Range

The Linear Dynamic Range (LDR) was determined for each element and met the criterion in Section 10.4 of SW-846 6010C as found in Table III. That is, the upper linear range was established by analyzing standards against the same calibration used for analyzing samples and obtaining recoveries within ±10% of the known concentration value. The Lower Limit of Quantitation was confirmed through the analysis of the Lower Level Check Standard (LLICV and LLCCV) and obtaining recoveries within ±30% of the known concentration value. The LLICV and LLCCV were run at a concentration of500ug/Lforthisstudy.

Memory Effects

Memory effect studies were performed to obtain the rinse time needed between sample measurements using the ESI FAST system. The elements studied were the most likely elements to be high for envi-ronmental samples run under SW 846: Al,Ca,Fe,K,Mg,andNa.Allofthedatacan be found in Figure 2. Five blanks were run, then five standards, then five blanks again to obtain the rinse out profiles. Al,Ca,Mg,andNawererunat500mg/L.Fe was run at 200 mg/L and K was run at 50mg/L.TheFASTparametersusedwerethe same as listed in Table II above.

5

Table III. Instrument Detection Limit (IDL) Data and Linear Dynamic Ranges (LDR).

Analyte Wavelength IDL IDL IDL 6010C, LDR,

RUN 1 RUN 2 RUN 3 IDL, ug/L mg/L

Ag 328.068 0.159 0.103 0.172 0.14 100

Al 308.215 1.732 0.630 1.898 1.42 2000

As 188.979 0.349 0.415 0.774 0.51 100

B 249.677 4.504 1.400 1.109 2.34 2000

Ba 233.527 0.056 0.016 0.034 0.04 25

Be 234.861 0.034 0.018 0.075 0.04 50

Ca 317.933 0.544 0.550 0.783 0.63 900

Cd 226.502 0.041 0.037 0.073 0.05 100

Co 228.616 0.076 0.092 0.078 0.08 250

Cr 267.716 0.086 0.099 0.071 0.09 100

Cu 327.393 0.062 0.047 0.158 0.09 300

Fe 259.939 0.256 0.230 0.168 0.22 400

K 766.49 7.269 5.270 5.499 6.01(0.24) 2000

Mg 279.077 1.763 2.030 3.108 2.30 700

Mn 257.61 0.005 0.009 0.018 0.01 40

Mo 202.031 0.132 0.097 0.180 0.14 125

Na 589.592 1.147 2.364 1.609 1.71(0.2) 900

Ni 231.604 0.178 0.188 0.161 0.18 125

Pb 220.353 0.427 0.229 0.368 0.34 100

P 213.617 1.543 1.091 1.249 1.29 3000

Li 670.784 0.214 0.176 0.364 0.25(0.03) 200

Sb 206.836 0.662 0.586 0.226 0.49 100

Se 196.026 0.875 0.953 0.485 0.77 100

Si 251.611 2.546 0.569 1.080 1.40 2500

Sr 421.552 0.025 0.029 1.139 0.40(0.01) 50

Sn 189.927 1.928 1.218 0.095 1.08(0.35) 2000

Ti 334.94 0.017 0.018 1.863 0.63 50

Tl 190.801 0.574 0.568 0.114 0.42 100

V 292.402 0.070 0.059 0.781 0.30 50

Zn 206.2 0.051 0.039 0.086 0.06 100

( ) = Axial

Quality Control and Sample Analysis

The accuracy and precision of the implementation of Method 6010C was demonstrated through the analysis of several reference materials and a local filtered, treated surface water sample (Lake Michigan). The quality control procedures specified in SW-846 were followed throughout the work performed. Immediately following calibration, the ICV (second source), LLICV, and ICB were analyzed and all results were determined to be within method-specified criteria, ±10%, ±30%, and <LLQC respectively. Following the analysis of each sequence of ten samples, the CCV, LLCCV, and CCB were analyzed and found to be within the method-specified criteria (same as for ICV, LLICV, and ICB). In additional to the sequential run QC (10% frequency), batch QC samples were also prepared and analyzed. As all

6

Figure 2. Above figures show the rinse out time using the ESI FAST system. Al, Ca, Mg, and Na were run at 500 mg/L. Fe was run at 200 mg/L and K was run at 50 mg/L. Samples were rinsed out to near baseline in 7 seconds.

samples analyzed were synthetic or natural water samples with no detectable turbidity or suspended solids, no acid digestion procedures were performed. The batch QC consisted of a method blank, a sample duplicate (DUP), a Laboratory ControlSample(LCS),aMatrixSpike(MS),andaMatrixSpike Duplicate (MSD). A natural surface water sample was used to prepare the DUP, MS, and MSD. Results of all batch QC samples were found to be within method-specified criteria. That is, no elements were detected within 10% of the LLQC, all elements detected in the sample and the sample DUP above the LLQC had relative percent differences of less than 20, all elements in the LCS were recovered within 20% of the known spike concentration, all elements in both the MSandMSDrecoveredwithin25%oftheknownspikeconcentration, and all spiked elements in the MS and MSD had relative percent differences of less than 20.

In addition to the batch QC samples, several reference materials were analyzed and included two Standard Reference Materials®(SRM)fromtheNationalInstitute of Standards & Technology (NIST),oneCertifiedReferenceMaterial(CRM)fromtheNationalResearchCouncilCanada(NRCC),andtwocommerciallyavailable water Proficiency Test (PT) samples.TheNISTsamplesincludedSRM1643e Trace Elements in Water and SRM 1640TraceElementsinNaturalWater.TheNRCCsamplewasSLRS-4RiverWaterReference Material for Trace Metals. This CRM is typically used for ICP-MS instru-mentation due to the low concentrations of elements, however, it has been included toshowtheexcellentsensitivityoftheOptima 7300 DV. The two commercial PT samples included WP Trace Metals and WS Trace Metals. Results of all five refer-ence materials are presented in Table IV – Table VIII.

Stability

The Continuing Calibration Verification (CCV) standard was analyzed repeatedly throughout each analytical run and no less frequently than after every 10 sam-ples. The recoveries for each of the CCVs obtained have been plotted against time for a period of four hours. The results are shown in Figure 3. All 30 elements moni-tored in this study were well within the method-specified acceptance criterion of ±10% of the known value. Typical drift for most elements was less than 3%.

Data Handling

All data obtained from the Optima 7300 DV was collected using the WinLab32 software loaded on a desktop PC attached to the instrument. Analytical results were computed using the WinLab32 software andexportedintoMicrosoft® Excel®. The textanddatatablesusedinthisreportwere created using Microsoft®Excel® and Word.

7

Figure 3. Four hour CCV stability.

Table IV. NIST 1640 Trace Elements in Natural Water. Certified Run 1 Run 2 Average mg/L units % REC.

Ag 328.068 0.007683478 0.007578301 0.00763089 0.0076 100

As 188.979 0.027794979 0.027058423 0.027426701 0.027 102

B 249.677 0.321778774 0.31648758 0.319133177 0.3 106

Ba 233.527 0.148039192 0.146252596 0.147145894 0.148 99

Ca 317.933 7.287467245 7.29179424 7.289630743 7.045 103

Cd 226.502 0.02461 0.024202 0.024406 0.0228 107

Co 228.616 0.022373993 0.022173326 0.02227366 0.022 101

Cr 267.716 0.041212275 0.040675621 0.040943948 0.0386 106

Cu 327.393 0.090707058 0.088824718 0.089765888 0.0852 105

Fe 259.939 0.034529324 0.033692193 0.034110759 0.0343 99

K 766.490 1.015084221 1.007176206 1.011130214 0.994 102

Mg 279.077 5.648166692 5.633282915 5.640724804 5.819 97

Mn 257.610 0.124362054 0.122821057 0.123591555 0.1215 102

Mo 202.031 0.049788978 0.049545748 0.049667363 0.04675 106

Na 589.592 29.22808031 28.92173556 29.07490794 29.35 99

Ni 231.604 0.029560106 0.029416086 0.029488096 0.0274 108

Pb 220.353 0.027413987 0.027680616 0.027547302 0.02789 99

Li 670.784 0.05139438 0.050218507 0.050806444 0.0507 100

Se 196.026 0.023501 0.023504 0.0235025 0.022 107

Si 251.611 4.747666191 4.644475617 4.696070904 4.73 99

Sr 421.552 0.12522384 0.125293217 0.125258528 0.124 101

V 292.402 0.013012505 0.012822827 0.012917666 0.013 99

Zn 206.200 0.057402 0.056602 0.057002 0.0532 107

Be 234.861 0.036510499 0.036158461 0.03633448 0.035 104

8

Table V. NIST 1643e Trace Elements in Water. Certified Run 1 Run 2 Average mg/L units % REC.

Ag 328.068 0.00082799 0.000982703 0.000905346 0.001 91

Al 308.215 0.14958319 0.145968533 0.147775861 0.142 104

As 188.979 0.05863297 0.060202348 0.059417659 0.0605 98

Ba 233.527 0.526201428 0.53185025 0.529025839 0.544 97

Ca 317.933 31.36350994 31.38490986 31.3742099 32.3 97

Cd 226.502 0.006803606 0.006802601 0.006803103 0.00657 104

Co 228.616 0.027229571 0.027465911 0.027347741 0.02706 101

Cr 267.716 0.021901845 0.021954832 0.021928339 0.0204 107

Cu 327.393 0.022717423 0.022755897 0.02273666 0.02276 100

Fe 259.939 0.09995466 0.10046584 0.10021025 0.0981 102

K 766.490 2.115235445 2.134464228 2.124849837 2.034 104

Mg 279.077 7.594261315 7.676997678 7.635629497 8.037 95

Mn 257.610 0.036795431 0.037161031 0.036978231 0.03897 95

Mo 202.031 0.127822547 0.128341294 0.128081921 0.1214 106

Na 589.592 19.36434423 19.37433937 19.3693418 20.74 93

Ni 231.604 0.062047849 0.062322707 0.062185278 0.0624 100

Pb 220.353 0.017716846 0.018946104 0.018331475 0.01963 93

Li 670.784 0.018412973 0.018762553 0.018587763 0.0174 107

Sb 206.836 0.056414629 0.057170312 0.05679247 0.0583 97

Se 196.026 0.011186647 0.012221246 0.011703946 0.01197 98

Sr 421.552 0.313265799 0.31293833 0.313102065 0.323 97

Tl 190.801 0.006104 0.00703 0.006567 0.007445 88

V 292.402 0.036212595 0.036634849 0.036423722 0.03786 96

Zn 206.200 0.074767001 0.075143809 0.074955405 0.0785 95

Be 234.861 0.014348862 0.014500296 0.014424579 0.014 103

Table VI. National Reasearch Council Canada

Riverine Water. Certified Run 1 mg/L units % REC.

Ca 317.933 6.088272145 6.2 98

Fe 259.939 0.108512603 0.103 105

K 766.490 0.671190352 0.68 99

Mg 279.077 1.544935545 1.6 97

Na 589.592 2.189781306 2.4 91

Sn 189.927 0.028264829 0.0263 107

K 766.490 0.000887947 0.00093 95

Mg 279.077 0.661790584 0.68 97

Na 589.592 1.660975302 1.6 104

Li 670.784 2.193887808 2.4 91

Be 234.861 0.058305976 0.054 108


Copyright ©2009, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners. 008773A_01


Table VIII. WS Trace Metals. Certified Run 1 Run 2 Average mg/L units % REC.

Ag 328.068 0.205841482 0.206784064 0.206312773 0.201 103

Al 308.215 1.503360942 1.509021475 1.506191209 1.5 100

As 188.979 0.04707919 0.048926848 0.048003019 0.0485 99

Ba 233.527 0.67227925 0.67399818 0.673138715 0.647 104

Be 313.107 0.009084418 0.009042679 0.009063548 0.0087 104

Cd 226.502 0.00998403 0.01004741 0.01001572 0.00927 108

Cr 267.716 0.136730412 0.137652362 0.137191387 0.132 104

Cu 327.393 0.715153403 0.720991073 0.718072238 0.677 106

Fe 259.939 0.913585704 0.915318141 0.914451923 0.93 98

Mn 257.610 0.358912563 0.357960513 0.358436538 0.366 98

Mo 202.031 0.043977706 0.044482171 0.044229939 0.0437 101

Ni 231.604 0.109153638 0.109458221 0.109305929 0.107 102

Pb 220.353 0.068196964 0.06857344 0.068385202 0.0668 102

Sb 206.836 0.043471699 0.042509311 0.042990505 0.0432 100

Se 196.026 0.074839851 0.074040603 0.074440227 0.0747 100

Tl 190.801 0.006336361 0.006970729 0.006653545 0.00717 93

V 292.402 0.480020599 0.481743476 0.480882038 0.456 105

Zn 206.200 0.712322194 0.711716612 0.712019403 0.706 101

Conclusion

The FAST system coupled with the Optima 7300 DV has been shown to produce results that meet the requirements outlined in U.S. EPA Method SW-846 while doubling sample productivity when compared to analyses with conventional introduction systems. Since the FAST system eliminates virtually all of the rinse and read delay times, most of the time is now spent running samples, therefore increasing productivity. The user will also have much less torch and injector mainte-nance since the system will see the sample matrixforamuchshorterperiodoftime.Also, since the FAST reaches a steady state signal much more quickly than conventional sample introduction, instrument detection limits are improved almost 2-fold for many analytes. Consequently, the Optima 7300 DV when used in conjunction with the SC-FAST autosampler provides a rugged, automated sample introduction system that can significantly reduce labor costs and improve laboratory productivity.

Table VII. WP Trace Metals. Certified Run 1 Run 2 Average mg/L units % REC.

Ag 328.068 0.415039553 0.415691157 0.415365355 0.4 104

Al 308.215 2.161214156 2.178741769 2.169977963 2.25 96

As 188.979 0.206215282 0.211098072 0.208656677 0.198 105

Be 313.107 0.104177959 0.104164917 0.104171438 0.107 97

Cd 226.502 0.162228771 0.162383871 0.162306321 0.162 100

Co 228.616 0.596703569 0.596119333 0.596411451 0.575 104

Cr 267.716 0.172615602 0.172950538 0.17278307 0.162 107

Cu 327.393 0.405182422 0.405208121 0.405195272 0.378 107

Fe 259.939 1.392941099 1.392462656 1.392701878 1.41 99

Mn 257.610 1.925099213 1.927471996 1.926285605 1.95 99

Ni 231.604 0.325614799 0.326326585 0.325970692 0.317 103

Pb 220.353 0.475584088 0.478602286 0.477093187 0.496 96

Se 196.026 0.752168839 0.766870842 0.75951984 0.721 105

Sr 421.552 0.122143791 0.122530301 0.122337046 0.122 100

Tl 190.801 0.65022971 0.657954117 0.654091913 0.633 103

V 292.402 1.122841516 1.12365243 1.123246973 1.13 99

Zn 206.200 0.610901508 0.611869781 0.611385645 0.613 100

Be 234.861 0.101283259 0.101227224 0.101255241 0.107 95

Abstract

The application of an SC-FAST sample introduction system to the analysis of natural and certified water samples is described. The SC-FAST system consists of an autosampler, sample loop, switching valve, high efficiency nebulizer and a glass cyclonic spray chamber to perform analysis by direct nebulization. The potential benefits of this introduction system are numerous and include: increased throughput, reduced memory effects, increased stability, lower reagent consumption and reduced instrument maintenance. These parameters are evaluated as the system is applied to U.S. EPA Method 200.7 Version 4.4.

Results indicate that sample throughput can be nearly tripled while still meeting the requirements outlined in Method 200.7. Sample-to-sample analysis (according to Method 200.7 protocol) is accomplished in 77 s with significantly improved washout compared to ICP-OES analysis by conventional introduction.

Introduction

The analysis of drinking water and wastewater for trace metal contamination is an important step in ensuring human and environmental health. More productive analyses make better use of public dollars and provide laboratories with a better cost of ownership for instrumentation. One way to improve productivity for metals analysis is by using a more sophisticated and automated sample introduction system to maximize the time spent on measurements and minimize the time spent on wash-in and wash-out of the sample. This work describes the coupling of the Optima™ 7300 DV with the ESI SC-FAST sample introduction system applied to a rigorous U.S. EPA method, drinking water/wastewater 200.7. Initial demonstration of capability and continuing quality control checks are measured as a demonstration of the method performance.

Inductively Coupled Plasma – Optical Emission Spectroscopy


Authors

Laura Thompson

Zoe Grosser, Ph.D.

Paul Krampitz


Increased Sample Throughput for ICP-OES Applied to U.S. EPA Method 200.7

The SC-FAST sample introduction system consists of an autosampler, sample loop, vacuum pump, 6-port switching valve, a sea spray nebulizer and utilizes flow injection to perform analysis by direct nebulization. The FAST system provides a number of advantages over conventional ICP-OES introduction systems, the most significant of which is higher sample throughput and reduced memory effects. The sample loop is in close proximity to the nebulizer which reduces the time required for sample uptake. Furthermore, the sample loop prevents samples from contacting the peristaltic pump tubing, which greatly improves sample washout. In addition to higher throughput and reduced memory effects, the FAST system allows for the online addition of internal standards which simplifies sample preparation and helps minimize errors and contamination.

Summary of Method

EPA Method 200.7 contains a lengthy description of proce-dures that should be followed when collecting, preserving and preparing samples for analysis. The details concerning instrument performance, quality control, and daily analysis routines are loosely defined and are, therefore, open to various interpretations1. For the sake of clarity, the proce-dure followed in this work is summarized in Table 1.

Table 1. Summary of U.S. EPA Method 200.7.

Establish Initial Performance Data

1. Linear Range

2. Perform IDLs and MDLs

3. Analyze Quality Control Samples with acceptable performance

Daily Analysis

1. Light plasma, allow 15 minutes for warm-up

2. Record Instrument Sensitivity

a. Use 1 ppm Mn for axial view, 10 ppm Mn for radial view

b. Record the counts for each and watch for significant changes as compared to signals obtained in previous days/weeks

3. Calibrate using blank and standards

4. Examine data and adjust background and measured wavelengths as needed

5. Screen new samples for relative levels and natural presence of internal std elements

6. Run instrument performance QCS

7. Run analytical QCS

8. Run samples

9. Review results of quality control samples for PASS/FAIL criteria

2

Experimental

Instrument

An Optima 7300 DV (PerkinElmer®, Shelton, CT) was used for the analysis of all samples described in this work. An SC-FAST (Elemental Scientific Inc., Omaha, NE) was coupled to the ICP-OES for sample introduction. The FAST system is controlled through the Optima WinLab32™ software and is shown schematically in Figure 1. The wavelengths monitored and the viewing modes used for the analytes in Method 200.7 are listed in Table 2. Instrument conditions for the Optima ICP-OES and FAST, as well as experimental parameters used throughout this work, are listed in Table 3.

Standards

All solutions were prepared using ASTM Type I (>18 MΩ-cm) water and double-distilled nitric acid. All acid concentra-tions reported in this document are described as a relative (v/v) percentage. Reference materials for this work were obtained from High Purity Standards (Charleston, SC) and from NIST, (Gaithersburg, MD).

Figure 1. Schematic of a FAST introduction system.

Table 3. FAST-Optima 7300 DV Instrumental Conditions and Experimental Parameters.

Optima 7300 DV Parameters

RF Power 1450 watts

Plasma Gas Flow 15 L min-1

Auxiliary Gas Flow 0.2 L min-1

Nebulizer Gas Flow 0.6 L min-1

Peristaltic Pump Speed 0.85 mL min-1

Nebulizer/Spray Chamber Sea Spray

Torch Cassette Position -3

Purge Normal

Resolution Normal

Integration Time 2 s min/5 s max

Read Delay 14 s

Wash Time 1 s

Number of Replicates 3

FAST Parameters

Sample Loop Volume 2 mL

Sample Loop Fill Rate 27 mL min-1

Carrier Pump Tubing Black/Black (0.76 mm i.d.)

Sample Load Time 7 s

Rinse 5 s

Analysis Time (total) 77 s (sample-to-sample)

Experimental Parameters

Carrier Solution 1% HNO3

Rinse Solution 1% HNO3

Acidity of Stds/Samples 1% HNO3

Sensitivity Check

Solutions containing 1 ppm Mn and 10 ppm Mn were analyzed periodically to monitor the sensitivity of the instrument. The Mn solutions were analyzed weekly and after the initial installation of the introduction system. The 1 ppm and 10 ppm Mn solutions were prepared by diluting 50 μL and 500 μL into 50 mL of 1% HNO3, respectively.

Internal Standards

All solutions were spiked with 1.5 ppm Y and 2.5 ppm of Te. The spiking solution was made from single element stock solutions.

Calibration

Since Method 200.7 outlines the analysis of water (both drinking water and wastewater) and soils, each element was calibrated to levels typically encountered in those samples. The concentrations used in the calibration standards are listed in Table 4. Each standard contained all elements listed in Table 4.

3

Table 2. Wavelengths Monitored and Viewing Modes Used for Method 200.7.

Wavelength Analyte Symbol Monitored (nm) View

Aluminum Al 308.215 Radial

Antimony Sb 206.836 Axial

Arsenic As 188.979 Axial

Barium Ba 233.527 Axial

Beryllium Be 313.042 Radial

Boron B 249.677 Radial

Cadmium Cd 226.502 Axial

Calcium Ca 315.887 Radial

Cerium Ce 413.765 Radial

Chromium Cr 267.716 Axial

Cobalt Co 228.616 Axial

Copper Cu 327.393 Axial

Iron Fe 238.204 Radial

Lead Pb 220.353 Axial

Lithium Li 670.784 Radial

Magnesium Mg 285.213 Radial

Manganese Mn 257.610 Axial

Mercury Hg 194.168 Axial

Molybdenum Mo 202.035 Axial

Nickel Ni 231.604 Axial

Phosphorus P 213.617 Axial

Potassium K 766.490 Radial

Selenium Se 196.026 Axial

Silicon Si 251.611 Axial

Silver Ag 328.068 Axial

Sodium Na 589.592 Radial

Strontium Sr 407.771 Radial

Thallium Tl 190.801 Axial

Tin Sn 189.927 Axial

Titanium Ti 334.940 Axial

Vanadium V 292.402 Axial

Zinc Zn 206.200 Axial

Internal Standards

Yttrium Y 371.029 Radial/Axial

Tellurium Te 214.281 Radial/Axial

Interference Check

Cerium Ce 413.764 Radial

The linear range results should be viewed with the under-standing that a combination of elements in the presence of a complicated matrix can cause interference effects and reduce the linear range for a number of elements. For results that more accurately reflect an individual experiment, the linear range should be established using standards in a matrix that replicates the sample matrix as closely as possible.

Table 5. Optima 7300 DV IDLs, MDLs and Linear Ranges for Method 200.7.

MDL IDL MDL Spike Linear Analyte Wavelength (ppb) (ppb) Level Range

Ag 328.068 0.5 1.1 5 100

Al 308.215 1.5 6.6 20 2000

As 188.979 1.8 1.2 20 100

B 249.677 2.0 (0.4) 1.9 (0.2) 5 2000

Ba 233.527 0.2 0.2 2 25

Be 313.107 0.2 0.5 2 50

Ca 317.933 1.3 (0.3) 1.0 (0.1) 5 900

Cd 226.502 0.4 0.4 2 100

Ce 413.764 7.6 (0.9) 12.8 (1.4) 20 100

Co 228.616 0.3 0.5 2 250

Cr 267.716 0.4 0.6 2 50

Cu 327.393 0.4 0.3 2 300

Fe 259.939 1.0 (0.5) 0.7 (0.2) 5 400

K 766.490 41.1 (2.1) 28.1 (3.6) 100 2000

Mg 279.077 2.5 (0.4) 4.6 (1.0) 20 700

Mn 257.610 0.1 0.5 2 40

Mo 202.031 0.4 0.5 5 125

Na 589.592 7.6 (0.2) 4.7 (0.5) 20 900

Ni 231.604 0.7 0.5 2 125

Pb 220.353 0.6 1.1 20 100

P 213.617 2.9 5.6 20 3000

Li 670.784 0.5 (0.01) 0.5 (0.1) 5 200

Hg 253.652 1.6 9.6 20 100

Sb 206.836 2.6 2.1 20 100

Se 196.026 1.1 1.8 20 100

Si 251.611 2.6 (1.3) 13.3 (4.7) 5 2500

Sr 421.552 1.6 (0.1) 1.6 (0.5) 2 50

Sn 189.927 5.6 (0.5) 6.7 (1.9) 20 2000

Ti 334.940 0.1 0.5 2 50

Tl 190.801 1.1 1.8 20 100

V 292.402 0.2 0.6 2 50

Zn 206.200 0.2 0.4 2 100

( ) = axial

Table 4. Calibration Standard Concentrations.

Analytes Standard Concentration μg L-1

Al, As, Ag, B, Ba, Be, Ca, Cd, Ce, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Si, Se, Sn, Sr, Ti, Tl, V, Zn 1000

Monitored Wavelengths

As mentioned earlier, the wavelengths monitored, along with the viewing mode used for each analyte in Method 200.7, are listed in Table 2. All analyses were performed using the instrument’s auto-integration feature with a minimum of 2 seconds and a maximum of 5 seconds.

Initial Performance Demonstration

IDLs

Instrument detection limits (IDLs) were estimated using multiple replicate measurements of the calibration blank (1% nitric acid). The IDL was calculated to be the concentration equal to three times the standard deviation of those replicate measurements; results are shown in Table 5. The IDL calcula-tion was followed according to the procedure outlined in Method 200.71.

MDLs

Method detection limits (MDLs) were based upon seven rep-licate measurements of a series of spiked calibration blanks. Each blank solution was spiked with analytes at concentra-tions between 2 and 10 times the calculated IDLs. The MDL was calculated by multiplying the standard deviation of the seven replicate measurements by the appropriate Student’s t test value according to:

MDL = (S) x (t)

Note that the Student's t-value is based on a 99% confi-dence level. Both the Student’s t-value and the standard deviation are based on n-1 degrees of freedom (t = 3.14 for six degrees of freedom).

Linear Range

A linear calibration range was established for each element listed in Method 200.7. No special detector optimization was done prior to conducting this procedure. The linear dynamic range for each analyte was calculated to be the highest concentration for which the recovery was within ±10% of the true (i.e., known) value of the standard. The results from this study are based upon multi-element stan-dards in a 1% nitric acid matrix and are given in Table 5.

4

drinking water sample. Certified reference materials were analyzed without modification to determine the accuracy as compared to the certified values. Recoveries of spiked reference materials and the local drinking water sample were calculated. Results from High Purity Standards “Trace Metals in Drinking Water”, NIST SRM 1643e “Trace Metals in Water” and a local drinking water sample are listed in Tables 6, 7 and 8, respectively. The results for the analysis of High Purity Standards interference check standards “INFCS I + INFCS IV” are listed in Table 9. Note that INFCS I was diluted 10,000 fold and INFCS IV was diluted 1,000 fold before the stan-dards were combined into one sample vial.

5

Data Handling

All data from the Optima 7300 DV was collected using a desktop computer attached to the instrument. The analytical results presented here were computed using the WinLab32 software and exported as report files. The text and support-ing data tables were generated using Microsoft® Word and Excel®.

Sample Analysis/Quality Control

The accuracy and precision of the above-described method were verified using certified reference materials and a local

Table 6. Precision and Recovery Data for High Purity “Trace Metals in Drinking Water” (CRM).

Avg Meas. Std. % Certified Recovery of Spike Avg. Spike Std. Dev. Conc. Dev. RSD Value Certified Level Recovery of Spike % Analyte μg L-1 μg L-1 μg L-1 μg L-1 Value (%) μg L-1 (%) Rec RSD

Ag --- --- --- 2 --- 100 99.4 0.8 0.6

As 69.9 0.7 1.0 80 87.4 100 102 3.0 2.9

B --- --- --- NA --- 100 99.7 1.1 1.1

Be 19.8 0.1 0.5 20 99.0 100 102 0.3 0.3

Ca 33400 18 0.1 35000 95.4 100 --- --- ---

Cd 9.66 0.2 1.7 10 96.6 100 101 1.0 1.0

Co 23.3 0.2 0.8 25 93.2 100 100 0.2 0.2

Cu 19.8 0.7 3.4 20 99.0 100 102 1.0 1.0

Cr 19.4 0.3 1.5 20 97.0 100 102 0.7 0.7

Fe 93.2 1.9 2.0 100 93.2 100 102 5.0 4.9

K 2380 31 1.3 2500 95.2 100 --- --- ---

Li 19.3 0.8 4.3 20 96.5 100 102 1.4 1.4

Mg 8530 125 1.5 9000 94.8 100 --- --- ---

Mn 38.6 0.5 1.3 40 96.5 100 103 1.2 1.1

Mo 101 0.7 0.6 100 101 100 101 1.6 1.6

Na 5580 6.9 0.1 6000 93.0 100 --- --- ---

Ni 57.8 0.5 0.9 60 96.3 100 98.6 2.5 2.6

Pb 39.7 3.1 7.7 40 99.2 100 103 2.9 2.8

Sb --- --- --- 10 --- 100 107 2.8 2.7

Se --- --- --- 10 --- 100 110 6.5 5.9

Sn --- --- --- NA --- 100 100 2.2 2.2

Sr 246 0.4 0.2 250 98.4 100 94.3 3.0 3.2

Ti --- --- --- NA --- 100 105 0.4 0.4

Tl --- --- --- 10 --- 100 99.5 4.7 4.7

V 29.8 0.4 1.4 30 99.3 100 103 0.5 0.5

Zn 69.5 0.6 0.9 70 99.3 100 98.8 1.6 1.7

NA = Not Applicable

6

Table 7. Precision and Recovery Data for NIST SRM 1643e “Trace Elements in Water”.

Rec. of Avg. Meas. Certified Certified Spike Avg. Spike Std. Dev. Analyte Conc. μg L-1 Std. Dev. μg L-1 % RSD μg L-1 Value μg L-1 Value (%) Level μg L-1 Recovery (%) of Spike Rec % RSD

Ag --- --- --- 1.062 --- 100 90.3 1.7 1.9

Al 133 0.3 0.3 141.8 94.1 100 94.0 1.1 1.2

As 60.2 1.9 3.7 60.45 99.6 100 109 4.3 4.0

B 150 0.3 0.2 157.9 95.0 100 98.5 2.4 2.4

Ba 504 11 2.1 544.2 92.6 100 --- --- ---

Be 13.6 0.1 0.5 13.98 97.3 100 104 0.5 0.4

Ca 29600 95 0.3 32300 91.6 100 --- --- ---

Cd 6.00 0.2 4.1 6.568 91.4 100 102 1.6 1.6

Co 25.2 0.2 0.6 27.06 93.1 100 103 0.9 0.9

Cr 20.4 0.2 0.8 20.40 100 100 105 1.0 0.9

Cu 23.6 0.3 1.2 22.76 101 100 108 0.2 0.1

Fe 97.6 7.0 7.2 98.1 99.5 100 99.7 4.8 4.9

K 1920 46 2.4 2034 94.4 100 --- --- ---

Li 18.3 0.9 5.0 17.4 105 100 104 0.8 0.8

Mg 7600 70 0.9 8037 94.5 100 --- --- ---

Mn 38.7 1.6 4.0 38.97 99.4 100 102 1.1 1.1

Mo 125 0.3 0.2 121.4 103 100 105 1.4 1.3

Na 19100 100 0.5 20740 92.1 100 --- --- ---

Ni 59.5 0.9 1.4 62.41 95.3 100 102 1.1 1.1

Pb 19.4 0.5 2.6 19.63 98.8 100 107 2.1 2.0

Sb 59.9 3.7 6.1 58.30 103 100 102 0.8 0.7

Se --- --- --- 11.97 --- 100 105 5.3 5.0

Sr 319 0.9 0.3 323.1 98.7 100 101 9.5 9.4

Sn --- --- --- n/a --- 100 104 0.03 0.03

Ti --- --- --- n/a --- 100 108 0.3 0.3

Tl --- --- --- 7.445 --- 100 106 6.4 6.1

V 37.0 0.2 0.5 37.86 97.7 100 107 0.6 0.6

Zn 76.6 0.7 0.9 78.5 97.6 100 101 0.7 0.6

NA = Not Applicable

7

Table 8. Results and Spike Recoveries for Local Drinking Water.

Low Spike Low Spike Low Spike High Spike High Spike High Spike Analyte Wavelength (nm) LDW Conc. μg L-1 Level μg L-1 Results μg L-1 % Recovery Level μgL-1 Results μg L-1 % Recovery

Al 308.215 7.50 100 100.3 100.3 500 475 95.0

As 188.979 < MDL 100 102.9 102.9 500 487 97.4

B 249.677 11.2 100 100.1 100.1 500 472 94.4

Ba 233.527 69.0 200 192.9 96.5 1000 946 94.6

Be 313.042 0.120 100 103.8 103.8 500 490 98.0

Ca 315.887 7120 100 --- --- 500 --- ---

Cd 226.502 < MDL 100 98.8 98.8 500 484 96.8

Co 228.616 < MDL 100 102.1 102.1 500 486 97.2

Cr 267.716 < MDL 100 101.6 101.6 500 484 96.8

Cu 327.393 97.6 100 106 106 500 478 95.6

Fe 238.204 83.5 100 94.5 94.5 500 491 98.2

K 766.490 877.7 100 --- --- 500 --- ---

Li 670.784 < MDL 100 102 102 500 492 98.4

Mg 285.213 1710 100 --- --- 500 --- ---

Mn 257.610 16.4 100 102 102 500 503 101

Mo 202.035 < MDL 100 101 101 500 480 96.0

Na 589.592 12800 100 --- --- 500 --- ---

Ni 231.604 0.730 100 99.4 99.4 500 482 96.4

P 213.617 < MDL 100 99.0 99.0 500 476 95.2

Pb 220.353 < MDL 100 99.7 99.7 500 487 97.4

Sb 206.836 < MDL 100 102 102 500 492 98.4

Se 196.026 < MDL 100 105 105 500 525 105

Sn 189.927 2.94 100 97.4 97.4 500 475 95.0

Sr 407.771 52.4 100 101 101 500 488 97.6

Ti 334.940 < MDL 100 103 103 500 503 101

Tl 190.801 < MDL 100 104 104 500 475 95.0

V 292.402 0.220 100 103 103 500 487 97.4

Zn 206.200 47.2 100 100 100 500 478 95.6

Table 9. Results for High Purity INFCS I + INFCS IV.

INFCS Run #1 INFCS Run #2 INFCS Avg. Duplicate INFCS True Analyte Wavelength (nm) μg L-1 μg L-1 Result μg L-1 RPD Value μg L-1 % Recovery

As 188.979 110 111 111 0.8 100 111

Ba 233.527 30.0 28.5 29.3 5.2 30 97.7

Be 313.042 10.9 10.9 10.9 0.1 10 109

Ca 315.887 4950 4910 4930 0.8 5000 98.6

Cd 226.502 32.2 33.2 32.7 2.9 30 109

Co 228.616 31.0 31.5 31.3 1.6 30 104

Cr 267.716 31.5 31.4 31.5 0.4 30 105

Cu 327.393 31.3 31.1 31.2 0.5 30 104

Fe 238.204 5230 4910 5070 6.2 5000 101

Hg 194.168 4.97 5.54 5.30 10.8 5 105

K 766.490 2130 2150 2140 0.7 2000 107

Mg 285.213 5070 5050 5060 0.3 5000 101

Mn 257.610 20.8 19.5 20.1 6.4 20 100

Ni 231.604 30.9 31.5 31.2 2.1 30 104

Pb 220.353 105 108 106 2.9 100 106

Se 196.026 53.9 48.8 51.4 10.1 50 103

Tl 190.801 102 103 103 1.1 100 103

V 292.402 31.1 31.1 31.1 0.2 30 104

Zn 206.200 34.8 32.6 33.7 6.7 30 112




Conclusions

The FAST system coupled with the Optima 7300 DV has been shown to produce results that meet the requirements outlined in U.S. EPA Method 200.7 while increasing sample productivity over 200% when compared to analyses with conventional introduction systems. Since the FAST system eliminates virtually all of the rinse and read delay times, most of the time is now spent running samples, therefore increasing productivity. Also, since the FAST reaches a steady state signal much more quickly than conventional sample introduction, instrument and method detection limits are improved almost 2-fold for many analytes. When used in conjunction with the SC autosampler and Optima 7300 DV, the FAST system provides a rugged, automated sample introduction system that can significantly reduce labor costs and improve laboratory productivity.

Acknowledgement

We would like to thank Maura Mahar, a graduate student at University of Massachusetts and summer intern for her excellent work contributing to this application. Special thanks also to Stan Smith, PerkinElmer Product Specialist and to Matthew Knopp of ESI for their time and input.

References

1. EPA Method 200.7, “Determination of Metals and Trace Metals in Water and Wastes by Inductively Coupled Plasma-Atomic Emission Spectrometry,” Revision 4.4, 1994, Environmental Monitoring Systems Laboratory, Office of Research and Development, United States Environmental Protection Agency, Cincinnati, OH 45268.

Summary

Mercury has long been recognized as a serious global pollutant that has a significant impact upon our ecosystem. Unlike most other pollutants, it is highly mobile, non-biodegradable, and bio-accumulative and as a result has to be closely monitored to ensure its harmful effects on local populations are minimized. Approximately 50 tons of mercury particulates are emitted into the atmosphere every year by a variety

of different man-made and natural sources including coal-fired power plants, solid waste incineration plants, volcanoes and forest fires. When the mercury falls back to earth it is deposited on the land and gets into the soil, river sediments and water ecosystems, where it is converted into the highly toxic organo mercury compound, methyl mercury (CH3Hg+). This toxicant enters both the plant and aquatic system food chain, and eventually ends up in the crops, vegetables and seafood we consume.

This application note will focus on a rapid test method for determining mercury directly in soils and river sediments using the principles of thermal decomposition, amalgamation and detection by atomic absorption described in EPA Method 7473 and ASTM Method 6722-01. Because there is no sample dissolution required, this novel approach can determine the total mercury content of a soil or sediment sample in less than five minutes, which is significantly faster than the traditional wet chemical reduction method.

Atomic Absorption


The Determination of Total Mercury in Soils and River Sediments Using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption

2

Study

The goal of this study was to evaluate a novel approach for the determination of total mercury in an SRM (standard ref-erence material) soil and an SRM river sediment directly in the solid material using aqueous calibration standards. The SRM soil was NIST 2709, while the SRM river sediment was NIST 8406.

Instrumentation

The SMS 100 mercury analyzer (PerkinElmer, Inc., Shelton, CT) was used for the study. This is a dedicated mercury analyzer for the determination of total mercury in solid and liquid samples using the principles of thermal decomposition, amalgamation and atomic absorption described in EPA Method 7473 (5) and ASTM Method 6722-016. The SMS 100 uses a decomposition furnace to release mercury vapor instead of the chemical reduction step used in traditional liquid-based analyzers. Both solid and liquid matrices can be loaded onto the instrument’s autosampler and analyzed without acid digestion or sample preparation prior to analysis. Because this approach does not require the conversion of mercury to mercuric ions, lengthy sample pretreatment steps are unnecessary. As a result, there is no need for reagents such as highly corrosive acids, strong oxidizing agents or reducing chemical, which means, no hazardous waste to be disposed of.

Principles of Operation

A small amount of the solid material (0.05-1.00 gms, depending on the mercury content) is weighed into a nickel sample boat. The boat is heated in an oxygen rich furnace, to release all the decomposition products, including mercury. These products are then carried in a stream of oxygen to a catalytic section of the furnace. Any halogens or oxides of nitrogen and sulfur in the sample are trapped on the catalyst. The remaining vapor is then carried to an amalga-mation cell that selectively traps mercury. After the system is flushed with oxygen to remove any remaining gases or decomposition products, the amalgamation cell is rapidly heated, releasing mercury vapor. Flowing oxygen carries the mercury vapor through an absorbance cell positioned in the light path of a single wavelength atomic absorption spectrophotometer. Absorbance is measured at the 253.7 nm wavelength as a function of the mercury concentration in the sample. A detection limit of 0.005 ng (nanogram) of mercury is achievable with a 25 cm path length cell, while a 2 cm cell allows a maximum concentration of 20 µg (microgram) of mercury. A schematic of the SMS 100 is shown in Figure 1.

Introduction

Mercury is distributed throughout the environment in a number of different forms. It is found as elemental mercury vapor in the atmosphere, while most of the mercury in water, sediments, soil, plants, and animals is found as inorganic and organic forms of the element. Natural sources of mercury come from volcanoes, forest fires and the weathering of mercury-bearing rocks. However, this is small compared to the vast amount of mercury which is generated from anthropogenic sources (human activities), such as fossil fuel combustion, solid waste incineration, mining and smelting, manufacture of cement and the use of mercury cells in the commercial production of chlorine.

Of all the anthropogenic activities, by far the largest polluters are coal-fired power plants, which release approximately 50 tons of elemental mercury into the atmosphere each year via the effluent generated by the combustion process1. Once released, the mercury particulates fall back down to the ground and get absorbed by soils, where they eventually get into commercial farming crops and vegetables. Mercury also enters surface waters, such as lakes, rivers, wetlands, estuaries and the open ocean, where it is converted to organic mercury (mainly methyl mercury – CH3Hg+) by the action of anaerobic organisms. The methyl mercury bio-magnifies up the aquatic food chain as it is passed from a lower food chain to a subsequently higher food chain level through feeding and eventually finds its way into the fish we eat.

As a result of this, the EPA considers there is sufficient evidence for methyl mercury to be considered a developmental toxicant that can potentially change the genetic material of an organism and thus increases the frequency of mutations above the natural background level2. At particular risk are women of childbearing age because the developing fetus is the most sensitive to the toxic effects of methyl mercury. It has been proven that children exposed to methyl mercury before birth may be at increased risk of poor performance on neuro-behavioral tasks, such as those measuring attention, fine motor function, language skills, visual-spatial abilities and verbal memory.

For that reason the EPA initiated the Clean Air Interstate Rule (CAIR)3 and the Clean Air Mercury Rule (CAMR)4 in March 2005, which is a two-phase plan to reduce the amount of mercury emission from coal-fired power stations from 48 tons to 15 tons by the year 2018, requiring new and improved mercury-specific control technology for power utilities.

Figure 2. Under similar operating conditions, different sample matrices generate similar absorbance values as shown by the straight line calibration graph obtained from different concentrations of mercury in widely different samples.

3

For this study, the soil and river sediment were calibrated against standards made up in dilute nitric acid. Calibration graphs of 0-50 ng and 50-500 ng of mercury were gener-ated from 0.1 and 1.0 ppm aqueous standards in 10% nitric acid respectively, by injecting different weights into a nickel sampling boat. The 0-50 ng calibration was obtained using the high sensitivity 25 cm optical path length cell, while the optional 2 cm cell was used for the 50-500 ng. The 0-50 ng calibration plot is shown in Figure 3, while the 50-500 ng plot is shown in Figure 4. The low calibration plot was then used to determine mercury in the SRM river sediment, while the high calibration plot was used for the SRM soil.

Operating Conditions

Table 1 shows the instrumental operating conditions for both the coal and fly ash samples.

Table 1. The SMS 100 operating conditions for both the SRM soil and sediment.

Parameter Setting

Sample Weight 0.500 gm (weighed accurately)

Sample Boat Nickel

Drying Temp/Time 300 °C for 45 sec

Decomposition Temp/Time 800 °C for 150 sec

Catalyst Temp 600 °C

Catalyst Delay Time 60 sec

Gold Trap Temp 700 °C for 30 sec

Measurement Time 90 sec

Oxygen Flow Rate 300 mL/min

Calibration

The SMS 100 measurement process involves the thermal generation of mercury vapor from the sample, which means the instrument can either be calibrated with aqueous standards or directly with solid certified reference materials. However, it is not critical that the calibration standards are of a similar matrix to the sample, because under similar operating condi-tions, different sample matrices generate similar absorbance values. This is shown by the straight line calibration graph in Figure 2 obtained from different concentrations of mercury in widely different samples, such as oyster tissue, dogfish, sediment and coal7.

Figure 1. A schematic of the SMS 100 mercury analyzer.

Figure 3. 0-50 ng mercury calibration plot in 10% nitric acid.




Conclusion

The study shows that the thermal decomposition, amalgamation and atomic absorption technique gives excellent correlation with standard reference materials for the determination of mercury in an SRM soil and river sediment. The fact that a sample can be analyzed in approximately 5 minutes using aqueous calibration standards, means the lengthy sample preparation steps associated with traditional wet chemical-based mercury analyzers can be avoided.

References

1. Pollution from FF Power Plants: http://en.wikipedia.org/wiki/Fossil_fuel_power_plant

2. Effects of Methyl Mercury: http://en.wikipedia.org/wiki/Methylmercury

3. EPA Clean Air Interstate Rule (CAIR) – http://www.epa.gov/CAIR/

4. EPA Clean Air Mercury Rule (CAMR) – http://www.epa.gov/oar/mercuryrule/

5. EPA Method 7473: http://www.epa.gov/osw/hazard/ testmethods/sw846/pdfs/7473.pdf

6. ASTM Method D6722-01: http://www.astm.org/Standards/D6722.html

7. Determination of Total Mercury in Coal and Fly Ash Using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption. PerkinElmer LAS Application Note # 008646_01: URL address if posted on your website.

Results

The SMS 100 results for the SRM soil and sediment are shown in Table 2.

Table 2. Determination of mercury in NIST SRM 2709 soil and SRM

8406 river sediment using the SMS 100.

Mercury Mercury Sample Certificate Measured % Matrix SRM Value (µg/g) Value (µg/g) Recovery

Soil NIST 2709 1.4 1.52 108.6

River Sediment NIST 8406 0.060 0.061 101.7

Figure 4. 50-500 ng mercury calibration plot in 10% nitric acid.

Summary

Mercury has long been recognized as a serious global pollutant that has a significant impact upon our ecosystem. Unlike most other pollutants, it is highly mobile, non-biodegradable, and bio-accumulative and as a result has to be closely monitored to ensure its harmful effects on local populations are minimized. Approximately 50 tons of mercury particulates are emitted into the atmosphere

every year by a variety of different man-made and natural sources including coal-fired power plants, solid waste incineration plants, volcanoes and forest fires. When the mercury falls back to earth it is deposited on the land and gets into the soil, river sediments and water ecosystems, where it is converted into the highly toxic organo mercury compound, methyl mercury (CH3Hg+). This toxicant enters both the plant and aquatic system food chain, and eventually ends up in the crops, vegetables and seafood we consume. In addition to being ingested via the food we eat, mercury can also enter the human body through contact with the skin and by inhalation into the lungs, where it can eventually end up in the bloodstream.

Atomic Absorption


The Determination of Total Mercury in Whole Blood Using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption

2

In addition to being ingested through the food we consume, mercury can also enter the body via the lungs and absorption through the skin. Repeated exposure to mercury has adverse health effects whose symptoms are well-documented. Individuals at high risk of exposure or those who are suspected of mercury intoxication are typically monitored through analysis of blood and urine samples. The mercury blood test will detect all types of mercury but because mercury remains in the bloodstream for only a few days, the test should be performed as soon after exposure as possible. It is important to emphasize that the only way that exposure to total mercury can be assessed, is by analyzing whole blood. The urine test only measures inorganic and elemental mercury, because organic forms of the element, particularly methyl mercury are not excreted from the human body.

As a result, the EPA considers there is sufficient evidence for methyl mercury to be considered a developmental toxicant that can potentially change the genetic material of an organism and thus increases the frequency of mutations above the natural background level.2 At particular risk are women of childbearing age because the developing fetus is the most sensitive to the toxic effects of methyl mercury. It has been proved that children who are exposed to methyl mercury before birth may be at increased risk of poor performance on neuro-behavioral tasks, such as those measuring attention, fine motor function, language skills, visual-spatial abilities and verbal memory. For that reason, the EPA has initiated the Clean Air Interstate Rule (CAIR)3 and the Clean Air Mercury Rule (CAMR)4 in March 2005, which is a two-phase plan to reduce the amount of mercury emission from coal-fired power stations from 48 tons to 15 tons by the year 2018, requiring new and improved mercury-specific control technology for power utilities.

This application note will focus on a rapid test method for determining mercury directly in whole blood using the principles of thermal decomposition, amalgamation and detection by atomic absorption described in EPA Method 7473 and ASTM Method 6722-01. Because there is very little sample preparation required, this novel approach can determine the total mercury content in whole blood samples in less than five minutes, which offers significant time-saving over traditional methods, which use dilution and/or acid digestion/oxidation followed by conventional chemical reduction using cold vapor atomic absorption spectrometry (CVAA).

Introduction

Mercury is distributed throughout the environment in a number of different forms. It exists mainly as elemental mercury vapor in the atmosphere, while most of the mercury found in water, sediments, soil, plants, and animals is in the inorganic and organic forms of the element. Natural sources of mercury come from volcanoes, forest fires and the weathering of mercury-bearing rocks. However, this is small compared to the vast amount of mercury which is generated from anthropogenic sources (human activities), such as fossil fuel combustion, solid waste incineration, mining and smelting, manufacture of cement and the use of mercury cells in the commercial production of chlorine.

Of all the anthropogenic activities, by far the largest polluters are coal-fired power plants, which release approximately 50 tons of elemental mercury into the atmosphere each year via the effluent generated by the combustion process.1 Once released, the mercury particulates fall back down to the ground and get absorbed by soils, where it eventually gets into agricultural crops and vegetables. It also enters surface waters, such as lakes, rivers, wetlands, estuaries and the open ocean, where it is converted to organic mercury (mainly methyl mercury – CH3Hg+) by the action of anaerobic organisms. The methyl mercury bio-magnifies up the aquatic food chain as it is passed from a lower food chain to a subsequently higher food chain level through feeding and eventually finds its way into the fish we eat.

Figure 1. A schematic of the SMS 100 mercury analyzer. Figure 2. Under similar operating conditions, different sample matrices generate similar absorbance values as shown by the straight line calibration graph obtained from different concentrations of mercury in widely different samples.

3

Instrumentation

The SMS™ 100 mercury analyzer (PerkinElmer, Inc., Shelton, CT) was used for the study. This is a dedicated mercury analyzer for the determination of total mercury in solid and liquid samples using the principles of thermal decomposition, amalgamation and atomic absorption described in EPA Method 74737 and ASTM Method 6722-01.8 The SMS 100 uses a decomposition furnace to release mercury vapor instead of the chemical reduction step used in traditional liquid-based analyzers. Both solid and liquid matrices can be loaded onto the instrument’s autosampler and analyzed without acid digestion or sample preparation prior to analysis. Because this approach does not require the conversion of mercury to mercuric ions, the lengthy sample pretreatment and digestion steps mentioned earlier, are unnecessary. As a result, there is no need for reagents such as strong acids, oxidizing chemicals or reducing agents, which means there is no hazardous waste to be disposed of.


A small amount of the sample (0.05-1.00 gms, depending on the mercury content) is weighed into a nickel sample boat. The boat is heated in an oxygen rich furnace, to release all the decomposition products, including mercury. These products are then carried in a stream of oxygen to

The Study

Traditional methods for the determination of total mercury in environmental and biological samples typically involve dilution with a suitable surfactant and/or hotplate/micro-wave digestion using a highly corrosive acid, followed by oxidation with a strong oxidizing agent and finished off by the addition of a reducing agent to generate mercury vapor, which is then measured using cold vapor atomic absorption spectrometry.5 Besides being extremely labor intensive and time consuming, all the sample preparation steps are a potential source of contamination and error. Even though on-line methods have been developed over the years using flow injection techniques,6 it’s still difficult to fully automate, and as a result sample throughput is significantly affected. An additional disadvantage to this method is the need to dispose of all the hazardous chemicals used for the analysis.

The goal of this study was to therefore evaluate a novel approach using the principles of thermal decomposition, amalgamation and detection by atomic absorption to determine total mercury directly in a series of freeze-dried whole blood standard reference materials (Lypho 1, 2 and 3 SRMs) using aqueous calibration standards. The benefit of this approach is that very little sample preparation/pretreatment is required, which translates into an analysis time of less than five minutes per sample.

Figure 3. 0-50 ng mercury calibration plot in 10% nitric acid used for the analysis of Lypho 1 SRM.

Figure 4. 50-500 ng mercury calibration plot in 10% nitric acid used for the analysis of Lypho 2 and 3 SRMs.

For this study, all the freeze-dried Lypho SRMs were calibrated against standards made up in dilute nitric acid. Calibration graphs of 0-50 ng and 50-500 ng of mercury were generated from 0.1 and 1.0 ppm aqueous standards in 10% nitric acid respectively, by injecting different weights into a nickel sampling boat. The 0-50 ng calibration was obtained using the high sensitivity 25 cm optical path length cell, while the optional 2 cm cell was used for the 50-500 ng. The 0-50 ng calibration plot is shown in Figure 3, and the 50-500 ng plot is shown in Figure 4. Both calibration plots are displayed as absorbance against total mercury injected. The low calibration plot was then used to determine mercury in Lypho 1, and the high calibration plot was used for the Lypho 2 and 3 SRM samples.

Results

The SMS 100 results for all the Lypho SRMs evaluated are shown in Table 2.

Conclusion

The study shows that the thermal decomposition, amalgamation and atomic absorption technique gives excellent correlation with standard reference materials for the determination of mercury in a series of freeze-dried blood SRMs. The fact that a sample can be analyzed in approximately 5 minutes using aqueous calibration standards, means the lengthy sample preparation steps associated with the analysis of whole blood by traditional wet chemical-based mercury analyzers, can be avoided.

a catalytic section of the furnace. Any halogens or oxides of nitrogen and sulfur in the sample are trapped on the catalyst. The remaining vapor is then carried to an amalga-mation cell that selectively traps mercury. After the system is flushed with oxygen to remove any remaining gases or decomposition products, the amalgamation cell is rapidly heated, releasing mercury vapor. Flowing oxygen carries the mercury vapor through an absorbance cell positioned in the light path of a single wavelength atomic absorption spectrophotometer. Absorbance is measured at the 253.7 nm wavelength as a function of the mercury concentration in the sample. A detection limit of 0.005 ng (nanogram) of mercury is achievable with a 25 cm path length cell, while a 2 cm cell allows a maximum concentration of 20 µg (microgram) of mercury. A schematic of the SMS 100 is shown in Figure 1.


Table 1 shows the instrumental operating conditions for all the Lypho SRMs.

Table 1. The SMS 100 operating conditions for all three Lypho SRMs.

Parameter Setting


Sample Boat Nickel








Calibration

The SMS 100 measurement process involves the thermal generation of mercury vapor from the sample, which means the instrument can either be calibrated with aqueous standards or directly with solid certified reference materials. However, it is not critical that the calibration standards are of a similar matrix to the sample, because under similar operating conditions, different sample matrices generate similar absorbance values. This is shown by the straight line calibration graph in Figure 2 obtained from different con-centrations of mercury in widely different samples, such as coal9 river sediment,10 oyster tissue and dogfish samples.11

4

Table 2. Results of the direct determination of mercury in a series of freeze-dried blood SRMs using the SMS 100.

Certified Accepted Conc. Conc. Range Found Recovery Blood SRM (ppb) (ppb) (ppb) (%)

Lypho 1 9.6 7.7-11.6 9.08 94.8

Lypho 2 39 31-47 35.5 90.9

Lypho 3 73 58-87 66.7 91.4




References

1. Pollution from Fossil Fuel Power Plants: http://en.wikipedia.org/wiki/Fossil_fuel_power_plant




5. Ultratrace Analysis of Mercury and Methylmercury in Rain Water Using Cold Vapor Atomic Absorption Spectrometry: R. Ahmed, K. May and M. Stoeppler; Fresenius’ Anal. Chem., Vol. 326, pp. 510-516, (1987).

6. On-Line Microwave Sample Pretreatment for the Determination of Mercury in Blood by Flow Injection Cold Vapor Atomic Absorption: T. Guo and J. Baasner, Talanta, Vol. 40, No. 12, pp. 1927-1936, (1993)



9. Determination of Total Mercury in Coal and Fly Ash Using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption. PerkinElmer, Inc. Application: http://las.perkinelmer.com/content/ApplicationNotes/ APP_DeterminationMercuryCoalAmalgamation CoupledAtomicAbsorption.pdf

10. Determination of Total Mercury in Soils and River Sediments Using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption. PerkinElmer, Inc.

11. Determination of Total Mercury in Fish and Agricultural Plant Materials Using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption. PerkinElmer, Inc.

Introduction

The United States does not have specific regulations specifying the allowable lev-els of toxic elements in foods, but many other countries do. For example, Canada has a specific tolerance level for arsenic of 0.1 ppm in ready to serve fruit juices, nectars, and beverages1. The toxic nature of arsenic is such that chronic exposure to

the element can lead to internal cancers of the bladder and kidney, skin cancer, neurological effects, and cardiovascular disease.

Arsenic can find its way into food through a variety of paths. In the recent past, various organic arsenicals were used as herbicides and antimicrobial agents in growth fields as well as applied directly on fruits and fruit trees. Prior to 2003, arsenic was commonly used as a wood preservative. Sawing and/or sanding of this wood would yield arsenic contaminated sawdust. In some areas, arsenic is naturally found in rock formations and can enter soil and water which is used in the growth of food products. Foods can also be contaminated during manufac-turing, processing, packaging and transport processes.

Atomic Absorption


Authors

Lee Davidowski, Ph.D.

Praveen Sarojam, Ph.D.


Determination of Arsenic in Baby Foods and Fruit Juices by GFAAS

2

There are a few specific analytical challenges that an analyst must consider in the determination of arsenic in foods by GFAAS. Toxic elements, such as arsenic, which may be present in foods are biologically important at very low concentrations. The U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry (ATSDR) defines a minimal risk level for chronic inorganic arsenic exposure to be 0.0003 mg As/kg/day. For a 45 lb. child drinking a liter of fruit juice a day, the minimal risk level for that juice would then be about 6 µg/L. Therefore, the analytical technique employed for this application must have the capability to accurately measure arsenic in sample digestates at the sub-ppb concentration level.

A complete method has been developed for the determination of arsenic (As) in baby foods and baby fruit juices by Graphite Furnace Atomic Absorption Spectroscopy (GFAAS). This method includes sample preparation steps using microwave assisted closed vessel digestion. Foods come in a wide variety of complex sample types and matrices, but their fundamental major components are water and various carbohydrates. In this work, the samples were totally digested in a microwave oven so that the samples’ various carbohydrate matrices were completely destroyed prior to instrumental analysis. Microwave digestion has several analytical advantages for this type of analysis. Because the sample is placed in a sealed Teflon® polymer (PTFE) digestion vessel, contamination is minimized and there is no loss of volatile elements during the digestion procedure. In a sealed vessel, higher temperatures of digestion are reached thereby quickly yielding complete matrix decomposition. With the microwave system used here, each sample’s digestion process is thoroughly documented as to time, pressure and temperature. This gives an analytically repeatable and transferable digestion process.

Figure 1. Examples of samples used in this work.

Experimental

A Multiwave™ 3000 Microwave Oven (PerkinElmer®, Shelton, CT USA) was used for the microwave-assisted digestion. This is an industrial-type oven which can be equipped with various accessories to optimize the sample digestion. In this case, the foods were digested in the Rotor 8XF100 which is a rotor with 8 high pressure vessels made of PTFE-TFM and surrounded by a ceramic jacket. TFM is chemically modified PTFE that has enhanced mechanical properties at high tem-peratures compared to conventional PTFE. This vessel has a “working” pressure of 60 bar (580 psi) and can operate at temperatures up to 260 ˚C with an internal volume of 100 mL. All vessels’ temperatures were monitored with the IR Temperature Sensor Accessory. This device gives thermal protection to the reactions in all of the vessels by measuring the temperature remotely on the bottom surface of each vessel liner during the digestion process. Pressure is continu-ously monitored in all vessels using load-cell technology in the upper rotor plate.

Samples of fruit juices and solid fruit purees were weighed directly into the PTFE-TFM digestion vessel liners (Figure 2). Sample weights were approxi-mately 2 grams for the liquid juices and 1 gram for the fruit purees. To each sample, 6 mL of concentrated nitric acid and 0.5 mL of concentrated hydrochloric acid were added. A pre-digestion spike of arsenic

was added to some of the samples to measure analyte recovery through the digestion process. Some vessels contained only the acids with no sample to act as analytical reagent blanks. The vessels were sealed and placed into the rotor for the microwave digestion. The acids used were high purity GFS Chemical™ (Columbus, OH, USA) which are packaged in Teflon® containers. After the digestion process, the digestates were transferred to polypropylene 50-mL autosampler vials (PerkinElmer part number B0193234) and laboratory ASTM type I water was added to a final total weight of 25 grams.

Table 1. Microwave Digestion Program.

Step Power (Watts) Ramp (min) Hold (min) Fan Speed

1 750 10 10 1

2 1200 10 10 1

3 0 (cool-down) 0 15 3

Figure 2. The Multiwave Rotor.

3

Table 3. THGA Heating Program.

Step Temperature Ramp Time Hold Time Argon Gas (˚C) (sec) (sec) (mL/min)

1* 120 1 30 250

2 140 5 15 250

3 1100 10 15 250

4** 1900 0 5 0

5 2450 1 3 250

* = Injection Temperature = 100 ˚C. **= Atomization Step

Table 1 shows the power/time program used for the sample digestions. To ensure a safe digestion, the Multiwave 3000’s IR sensor measures the temperature of each vessel. If a vessel nears its maximum operating temperature of 260 ˚C, then the Multiwave oven will automatically decrease the applied power. Also, the pressure sensor sends data to the Multiwave oven controller during the digestion. The Multiwave oven will automatically reduce power if the maximum pressure of 60 bar is approached.

An AAnalyst™ 800 Atomic Absorption Spectrometer (PerkinElmer) was used for the GFAAS measurements of arsenic in the digested samples. The AAnalyst 800 features longitudinal Zeeman-effect background correction2 and a solid-state detector which is highly efficient at low wave-lengths (arsenics’s primary AA wavelength is 193.7 nm). The AAnalyst 800 uses a transversely heated graphite atomizer (THGA) which provides uniform temperature distribution across the entire length of the graphite tube. The THGA features an integrated L’vov platform3 which is useful in overcoming potential chemical interference effects common to the GFAAS technique.

For instrument calibration, a 10 µg/L As standard was prepared from serial dilutions of a 1000 mg/L stock standard (PE Pure, PerkinElmer Part Number N9300102). The AAnalyst 800 autosampler then prepared a calibration curve of 2.5, 5.0 and 10.0 µg/L from that 10 µg/L arsenic standard. A QC standard was also measured by this method, High Purity Standards TM-A, (Charleston, SC 29423) and is certified to be 10 µg/L arsenic. A mixed matrix modifier of palladium and magnesium nitrate was prepared by diluting and combining individual stock matrix modifier solutions. The mixed modifier solution is prepared by combining 5 mL of the stock palladium modifier (1% solution, PerkinElmer Part Number B0190635) and 0.5 mL of the magnesium nitrate stock modifier (PerkinElmer Part Number B0190634) and diluting to 50 mL with ASTM Type I water. Other instrumental parameters are given in Tables 2 and 3.

A typical calibration curve is shown in Figure 3 and calibration standard profiles are shown in Figure 4. The curve has good linearity and the sensitivity is good at low concentrations.

Table 2. AAnalyst 800 Instrumental Parameters.

Wavelength (nm) 193.7

Source Lamp (mA) EDL 380

Slit Width (nm) 0.7

Background Correction Zeeman-effect

Measurement Mode Peak Area, 3 replicates

Calibration Algorithm Linear thru Zero

Integration Time 5.0

Sample Volume 24

Matrix Modifier Volume 6

THGA Standard THGA Tube

Figure 3. Arsenic calibration curve.

Figure 4. Arsenic atomic profile signals for calibration standards and blank.




Table 4 shows the mean of the three replicate measurements for the food sample corrected for weight used and final volume, the standard deviation of those measurements (SD), and the relative standard deviation of the three replicates (%RSD). Also, the first seven samples shown were digested in duplicate. The difference between the two are shown in the column labeled % Diff. The relatively high percent differ-ences in the pear puree samples is due to the fact that the concentration of arsenic is very low in this sample, near the method detection limit for the puree of 3 ng/g.

For samples that were split and spiked with arsenic prior to digestion, that measure of the spike recovery is shown as the percentage of the recovery in the last column of Table 4. A recovery value of near 100% shows that there is little or no loss of analyte during the digestion process and that there are no unresolved matrix interferences with the analytical method.

Conclusion

It has been shown that this method can be successfully applied to the determination of arsenic in these types of foods. The Multiwave 3000 Digestion System gave completely digested, clear samples with no loss of arsenic during the high temperature, high pressure process. The AAnalyst 800 with longitudinal Zeeman-effect background correction and THGA tube containing the L’vov platform, gave good spike recoveries with no matrix interference. The detection limit estimated to be 3 ng/g was well below the Canadian limit of 100 ng/g in the original juice or puree and offers room for lower regulatory limits that may be established in the future to also be satisfactorily measured.

References

1. Department of Justice Canada, http://laws.justice.gc.ca/en/showdoc/cr/C.R.C.-c.870

2. Hadgu, G. and Frech, W. Spectrochim Acta 49B, 445 (1994).

3. L’vov, B.L., Spectrochim Acta, 45B, 633 (1990).

Results

The Multiwave 3000 Digestion System with the rotor-8 produced clear, fully digested, sample solutions. No filtration was necessary. The AAnalyst 800 gave a characteristic mass (Mo) of 36 pg for arsenic with these conditions which is in good agreement with the manufacturers recommended Mo value of 40 pg. Nine different samples of baby juice and puree foods were analyzed by this method. The fruit juices and one of the puree samples were prepared in duplicate to check the entire method’s reproducibility. These samples were also “spiked” prior to digestion with the equivalent in the undiluted sample of approximately 240 ng/g arsenic. The percent recovery of this spike will be used to check for any losses of arsenic during the digestion and to check for the presence of any matrix interferences. All of those data are given in Table 4.

Table 4. Results for the Analyses of Baby Foods by GFAAS.

Sample ID Mean SD %RSD % DIFF %Recovery (ng/g) (ng/g) of Spike*

B_Pear Juice 10.2 1.2 12 9.9 93.9

G_Pear Juice 15.1 0.65 4.3 3.3 90.0

B_Grape Juice 27.4 2.2 8.2 0.70 85.0

B_Apple Juice 12.4 0.96 7.8 3.4 92.6

G_Apple Juice 18.2 0.29 1.6 4.7

B_Cherry Juice 10.3 0.77 7.5 23

B_Pear Puree 5.00 2.0 35 55 95.7

G_Pear Puree <3

B_Apple Sauce <3

HP QC TM-A 10.0 0.051 0.51 99.9 (µg/L) (µg/L)

*Predigestion spike of 5 µg/L in the final solution or analysis

Summary

Mercury has long been recognized as a serious global pollutant that has a significant impact upon our ecosystem. Unlike most other pollutants, it is highly mobile, non-biodegradable, and bio-accumulative and as a result has to be closely monitored to ensure its harmful effects on local populations are minimized. Approximately 50 tons of mercury particulates are emitted into the atmosphere every year by a variety of

different man-made and natural sources including coal-fired power plants, solid waste incineration plants, volcanoes and forest fires. When the mercury falls back to earth it is deposited on the land and gets into the soil, river sediments and water ecosystems, where it is converted into the highly toxic organo mercury compound, methyl mercury (CH3Hg+). This toxicant enters both the plant and aquatic system food chain, and eventually ends up in the crops, vegetables and seafood we consume.

This application note will focus on a rapid test method for determining mercury directly in food materials and agricultural crops using the principles of thermal decomposition, amalgamation and detection by atomic absorption described in EPA Method 7473 and ASTM Method 6722-01. Because there is no sample dissolution required, this novel approach can determine the total mercury content in these types of samples in less than five minutes, which is significantly faster than the traditional wet chemical reduction method for quantifying mercury.

Atomic Absorption


The Determination of Total Mercury in Fish and Agricultural Plant Materials Using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption

2

Table 1. The standard reference materials evaluated in this study.

Sample Matrix SRM Name

Tuna BCR 463

Dogfish Muscle NRC Dorm 2

Dogfish Liver NRC Dolt 3

Spinach Leaves NIST 1570A

Apple Leaves NIST 1515

Wheat Flour NIST 8437

Instrumentation

The SMS™ 100 mercury analyzer (PerkinElmer Inc., Shelton, CT) was used for the study. This is a dedicated mercury analyzer for the determination of total mercury in solid and liquid samples using the principles of thermal decomposition, amalgamation and atomic absorption described in EPA Method 74735 and ASTM Method 6722-01.6 The SMS 100 uses a decomposition furnace to release mercury vapor instead of the chemical reduction step used in traditional liquid-based analyzers. Both solid and liquid matrices can be loaded onto the instrument’s autosampler and analyzed without acid digestion or sample preparation prior to analysis. Because this approach does not require the conversion of mercury to mercuric ions, lengthy sample pretreatment steps are unnecessary. As a result, there is no need for reagents such as highly corrosive acids, strong oxidizing agents or reducing chemical, which means, no hazardous waste to be disposed of.


A small amount of the solid material (0.05-1.00 gms, depending on the mercury content) is weighed into a nickel sample boat. The boat is heated in an oxygen rich furnace, to release all the decomposition products, including mercury. These products are then carried in a stream of oxygen to a catalytic section of the furnace. Any halogens or oxides of nitrogen and sulfur in the sample are trapped on the catalyst. The remaining vapor is then carried to an amalga-mation cell that selectively traps mercury. After the system is flushed with oxygen to remove any remaining gases or decomposition products, the amalgamation cell is rapidly heated, releasing mercury vapor. Flowing oxygen carries the mercury vapor through an absorbance cell positioned in the light path of a single wavelength atomic absorption spectrophotometer. Absorbance is measured at the 253.7 nm wavelength as a function of the mercury concentration in the sample. A detection limit of 0.005 ng (nanogram) of mercury is achievable with a 25 cm path length cell, while a 2 cm cell allows a maximum concentration of 20 µg (microgram) of mercury. A schematic of the SMS 100 is shown in Figure 1.

Introduction

Mercury is distributed throughout the environment in a number of different forms. It exists mainly as elemental mercury vapor in the atmosphere, while most of the mercury found in water, sediments, soil, plants, and animals is in the inorganic and organic forms of the element. Natural sources of mercury come from volcanoes, forest fires and the weathering of mercury-bearing rocks. However, this is small compared to the vast amount of mercury which is generated from anthropogenic sources (human activities), such as fossil fuel combustion, solid waste incineration, mining and smelting, manufacture of cement and the use of mercury cells in the commercial production of chlorine.

Of all the anthropogenic activities, by far the largest polluters are coal-fired power plants, which release approximately 50 tons of elemental mercury into the atmosphere each year via the effluent generated by the combustion process.1 Once released, the mercury particulates fall back down to the ground and get absorbed by soils, where it eventually gets into commercial farming crops and vegetables. It also enters surface waters, such as lakes, rivers, wetlands, estu-aries and the open ocean, where it is converted to organic mercury (mainly methyl mercury – CH3Hg+) by the action of anaerobic organisms. The methyl mercury bio-magnifies up the aquatic food chain as it is passed from a lower food chain to a subsequently higher food chain level through feeding and eventually finds its way into the fish we eat.

As a result of this, the EPA considers there is sufficient evi-dence for methyl mercury to be considered a developmental toxicant that can potentially change the genetic material of an organism and thus increases the frequency of mutations above the natural background level.2 At particular risk are women of childbearing age because the developing fetus is the most sensitive to the toxic effects of methyl mercury. It has been proved that children who are exposed to methyl mercury before birth may be at increased risk of poor performance on neuro-behavioral tasks, such as those measuring attention, fine motor function, language skills, visual-spatial abilities and verbal memory.

For that reason the EPA initiated the Clean Air Interstate Rule (CAIR)3 and the Clean Air Mercury Rule (CAMR)4 in March 2005, which is a two-phase plan to reduce the amount of mercury emission from coal-fired power stations from 48 tons to 15 tons by the year 2018, requiring new and improved mercury-specific control technology for power utilities.

Study

The goal of this study was to evaluate a novel approach for the direct determination of total mercury in a range of food and plant SRMs (standard reference material) using aqueous calibration standards. The samples evaluated are shown in Table 1.

3

plot is shown in Figure 4. The low calibration plot was then used to determine mercury in the spinach, apple leaves and wheat flour samples, while the high calibration plot was used for the tuna and dogfish samples,


Table 2 shows the instrumental operating conditions for all the SRMs.

Table 2. The SMS 100 operating conditions for all the SRMs.

Parameter Setting


Sample Boat Nickel








Calibration

The SMS 100 measurement process involves the thermal generation of mercury vapor from the sample, which means the instrument can either be calibrated with aqueous standards or directly with solid certified reference materials. However, it is not critical that the calibration standards are of a similar matrix to the sample, because under similar operating condi-tions, different sample matrices generate similar absorbance values. This is shown by the straight line calibration graph in Figure 2 obtained from different concentrations of mercury in widely different samples, such as oyster tissue, dogfish, coal7 and sediment samples.8

For this study, all the food and plant SRMs were calibrated against standards made up in dilute nitric acid. Calibration graphs of 0-50 ng and 50-500 ng of mercury were generated from 0.1 and 1.0 ppm aqueous standards in 10% nitric acid respectively, by injecting different weights into a nickel sampling boat. The 0-50 ng calibration was obtained using the high sensitivity 25 cm optical path length cell, while the optional 2 cm cell was used for the 50-500 ng. The 0-50 ng calibration plot is shown in Figure 3, while the 50-500 ng

Figure 1. A schematic of the SMS 100 mercury analyzer.

Figure 2. Under similar operating conditions, different sample matrices generate similar absorbance values as shown by the straight line calibration graph obtained from different concentrations of mercury in widely different samples.

Figure 3. 0-50 ng mercury calibration plot in 10% nitric acid used for the spinach, apple leaves and wheat flour samples.

Conclusion

The study shows that the thermal decomposition, amalga-mation and atomic absorption technique gives excellent correlation with standard reference materials for the determination of mercury in a range of fish and plant material SRMs. The fact that a sample can be analyzed in approximately 5 minutes using aqueous calibration standards, means the lengthy sample preparation steps associated with traditional wet chemical-based mercury analyzers can be avoided.

References

1. Pollution from FF Power Plants: http://en.wikipedia.org/wiki/Fossil_fuel_power_plant






7. Determination of Total Mercury in Coal and Fly Ash Using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption. PerkinElmer, Inc.

8. Determination of Total Mercury in Soils and River Sediments Using Thermal Decomposition and Amalgamation Coupled with Atomic Absorption. PerkinElmer, Inc.

Results

The SMS 100 results for all the SRMs evaluated are shown in Table 3.

Figure 4. 50-500 ng mercury calibration plot in 10% nitric acid used for the tuna and dogfish samples.




Table 3. Results of the direct determination of mercury in a range of fish and plant material SRMs using the SMS 100.

Certified Conc. Conc. Found Recovery Sample Matrix CRM Name (ppm) (ppm) (%)

Tuna BCR 463 2.85 3.04 105

Dogfish Muscle NRC Dorm 2 4.64 4.73 102

Dogfish Liver NRC Dolt 3 3.37 3.51 104

Spinach Leaves NIST 1570A 0.030 0.033 109

Apple Leaves NIST 1515 0.044 0.046 104

Wheat Flour NIST 8437 0.004 0.0042 105

Studies suggest that the isoflavones found in soy can exert positive physiological effects.

A P P L I C A T I O N N O T e

Liquid ChromatographyIncreased Throughput and Reduced Solvent Consumption for the Determination of Isoflavones by UHPLC

Introduction

All plant foods are complex mixtures of chemicals including both nutrients and biologically active non-nutrients, referred to as phytochemicals. Soy is known for having high concentrations of several physiologically-active phytochemicals, including isoflavones, phytate (inositol hexaphosphate), saponins, phytosterols and protease inhibitors. The isoflavones are what makes soy unique. Soy iso-flavones are non-steroidal molecules structurally and functionally related to 17β-estradiol. Soybeans and soy foods are the only natural dietary sources that provide nutritionally relevant amounts of iso-flavones.

Clinical studies suggest that consumption of isoflavones can exert positive physiological effects1. Recent data has demonstrated that isoflavones have potent antioxidant properties, comparable to that of the well known antioxidant vitamin E2. Research in several areas of healthcare has linked iso-flavones to lowering risks for disease, easing menopause symptoms, reducing heart disease and can-cer risk, and improving prostate and bone health. As a result of the potential health benefits of iso-flavones, many soy products and isoflavone supplements are available to consumers. These fall into a category of products known as nutraceuticals or functional foods, which provide a potential health benefit from a naturally occurring substance. This has created the need for an analytical technique which can qualify and quantify the type and amount of isoflavones in a nutraceutical product.

Authors:

Padmaja Prabhu, PerkinElmerWilhad Reuter, PerkinElmer

2

Experimental

The PerkinElmer® Flexar™ FX-10 UHPLC system was used for this application. A 1.5 µm particle, 50 mm length, C18 column was used to separate the analytes of interest and matrix. This col-umn required an operating pressure of approximately 8500 psi resulting in a mobile phase flow rate of approximately 0.7 mL/min. A Flexar FX-UV/Vis UHPLC detector was operated at 254 nm. Table 1 presents the detailed operating parameters of the UHPLC system. The instrument interaction, data analysis, and reporting was completed with the PerkinElmer, Chromera® data system.

This application note will demonstrate a rapid method for the identification and quantification soy isoflavones using ultra high performance liquid chromatography (UHPLC). This UHPLC method is nearly 10x faster, and saves 92% of the mobile phase solvent, compared to conventional HPLC methods.

The focus will be on three major isoflavones found in soy-beans, genistein, daidzein, and glycitein, and their glycosidic conjugates (Figure 1). In addition to qualitative and quanti-tative analysis, we will compare the analytical time and sol-vent use of this UHPLC application with a similar technique using conventional HPLC. The savings in both time and sol-vent consumption will be discussed. Lastly, three commer-cial formulations of supplements will be analyzed and isofla-vone identification and content determined.

Figure 1. Chemical structure of a common soy isoflavone, daidzein, and its glycosidic conjugate, daidzin

HPLC System PerkinElmer Flexar FX-10 UHPLC

Autosampler Flexar UHPLC Autosampler

Detector Flexar FX UV/Vis UHPLC Detector

Column Grace Vision HT C18 (50 mm x 1.5 μ, 2.1 mm i.d.)

Column Temperature 30 C

Detector Wavelength 254 nm

Injection Volume 2 μL (partial loop)

Flow Rate 1 mL/min

Mobil Phase A Water pH adjusted to 3.0 with orthophosphoric acid

Mobil Phase B Acetonitrile Gradient Program

Type Time Flow % A % B Curve (min) (mL/min)

Equil 0.5 0.7 90 10 0

Run 0.3 0.7 90 10 0

Run 0.3 0.7 85 15 0

Run 0.8 0.7 80 20 0

Run 0.9 0.7 75 25 0

Run 0.5 0.7 65 35 0

Run 0.5 0.7 90 10 0

Run 1.2 0.7 90 10 0

Table 1: Detailed instrument conditions used in the determination of isoflavones.

Figure 2. Resultant chromatograms of the analysis of reference material under the instrument conditions presented here (overlay of three replicates).

3

Standard preparation: The reference standards were procured from Chromadex (Irvine, CA).

Stock Solution: 1 mg of each of daidzin, glycitin, genistin, daid-zein, glycitein and genistein were dissolved in 10 mL of water:acetonitrile (1:1), making a stock solution at a concentra-tion of 100 µg/mL.

Calibration curve: The stock solution (100 µg/mL) was diluted in 9:1 (water:acetonitrile) to create an 8 level calibration (Table 2). The three low calibration points were serially diluted from the 10 µg/mL level, to reduce inaccuracies in the measurement to small volumes. The diluent in the calibration curve was used so that the solvent composition was as close as possible to the mobile phase composition at the time of injection. This will mini-mize baseline disturbance associated with injection. This is espe-cially important in UHPLC where peak shapes can be distorted as a result of disturbance of the mobile phase composition.

Calibration Concentration Volume of Final Volume Level (µg/mL) Standard Solution (mL) Added (mL)

1. 0.5 0.5* 10

2. 1 1* 10

3. 2 2* 10

4. 4 0.4 10

5. 6 0.6 10

6. 8 0.8 10

7. 10 1.0 10

8. 12 1.2 10

Table 2: Scheme used for the creation of an eight level calibration.

Calibration: The UV detector was calibrated across the range of 0.5 to 12 µg/mL, each calibration point was run in triplicate to demonstrate the precision of the system. The average coefficient of determination for a line of linear regression was 0.9965 for all 6 compounds. The calibration curves for daidzein and daidzin are pictured in Figure 3. Also in Figure 3 is the percent relative stan-dard deviation (%RSD) for each calibration point (n=3). The precision of the system across the calibration range is excellent, the %RSD for diadzein and diadzin with an average of approxi-mately 0.5%.

Sample preparation: Three commercially available supplements were analyzed with the method developed here. The samples are referred to as: sample 1, sample 2 and sample 3. The sample preparation used was relatively straightforward. A 0.5 gram sam-ple of each supplement was ground with a mortar and pestle. The ground sample was extracted in 100 mL of (1:1) water: acetoni-trile, in an ultrasonic bath. The sample extracts were filtered through a 0.2µm nylon filter. Following filtration, 2 mL of sample extract was diluted to 10 mL final volume in 9:1 (water:acetonitrile), this reduced the concentration of the isofla-vones in the extract within the range of the calibration curve and made the diluents and mobile phase more alike.

Figure 3. Example calibration results, via Chromera CDS.

4

Results

Under the conditions presented here, the analytical run was 4.5 minutes long with an elution order of daidzin, glycitin, genistin, daidzein, glycitein and genistein. In similar applications per-formed with conventional HPLC, the analytical run time was 43 minutes. Therefore, this method has reduced the run time by 38.5 minutes, while maintaining complete resolution of all ana-lyte peaks. The minimum resolution (critical pair) of analytes in this separation was 2.8, occurring between daidzin and glycitin.

The analysis of samples 1 and 2 resulted in detection of signifi-cant levels of isoflavones, with 49 and 52 mg of isoflavones in each sample, respectively. The label on the bottle for both sam-ples 1 and 2 stated that each contained 55 mg of isoflavones per tablet, the determined values for each sample equate to 89% and 95% recovery. The sample analysis is summarized in Table3. The analysis of sample 3 resulted in no detection of isoflavones; this was expected, as sample 3 was a multi-vitamin that did not list any isoflavones on its label.

Figure 4: Example chromatogram of sample 1.

Measured Isoflavone Labeled Isoflavone Percent Recovery Content (mg) Content (mg)

Sample 1 49 55 89%

Sample 2 52 55 95%

Sample 3 ND 0 n/a

Table 3. Summary of the results determined in the analysis of supplement samples for isoflavone content.

Conclusions

The technique presented in this application note applies UHPLC instrumentation to the determination of isoflavones in nutraceu-tical supplements. A commercial reference standard was used to identify 3 isoflavones and their glycosidic conjugates by retention time. The separation used a short small particle (1.5 µm) LC col-umn and achieved adequate resolution of all isoflavone peaks commonly found in soy materials. A multilevel calibration curve using the UV/Vis detector at 254 nm was used to quantitatively determine the amount of isoflavone in three dietary supplements. In addition to providing a precise and accurate result for the determination of isoflavones in supplements, this UHPLC appli-cation has reduced the analytical runtime by nearly 10x and elim-inated nearly 40 mL of solvent use per sample. When compared to conventional HPLC, this directly translates into solvent sav-ings of 92%.

References

1. www.soyconnection.com, IsofavonesFactSheet.pdf

2. http://www.isoflavones.info


Copyright ©2009, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners.

008849-01 Printed in USA

PerkinElmer, Inc.940 Winter Street Waltham, MA 02451 USA P: (800) 762-4000 or (+1) 203-925-4602www.perkinelmer.com

Introduction

D-Limonene, shown in Figure 1, is a common naturally occurring compound with a citrus scent. It is often used as an additive in food products and fragrances, and is classified by the U.S. Food and Drug Administration (FDA) as Generally Recognized as Safe (GRAS)1. It has also been approved by the U.S. Environmental Protection Agency (EPA) for usage as a natural pesticide and insect repellent1. Limonene has also been studied for its anti-carcinogenic properties2. Orange oil, which contains a

considerable amount of limonene, has numerous applications including a combustant in engines3, a powerful degreaser in cleaning applications, and a natural pesticide4. These uses may require a known concentration of limonene with a limited amount of impurities. This exemplifies the need for a reliable method of extraction of limonene from its natural source, citrus rinds, followed by a quantitative analysis of the extract for limonene and possible impurities.

A method for the extraction and quantification of limonene from citrus fruit peels is discussed in this applications note. Beyond demonstrating the use of GC/MS in the analysis of citrus fruit for limonene content, this application demonstrates a simple, inexpensive technique to introduce students to method development, calibration and quantification using a chromatographic technique. The analysis of citrus fruit for limonene may be an ideal laboratory assignment at the undergraduate level. The techniques used are safe, simple and easy.

Gas Chromatography/ Mass Spectrometry


Authors

Stephen Davidowski

Brian DiMarco


The Extraction and Quantification of Limonene from Citrus Rinds Using GC/MS

Figure 1. Molecular structure of limonene.

2

Table 1. Operation Specifications for GC.

Gas Chromatograph: PerkinElmer Clarus 500 GC

Analytical Column: Elite-5ms (30 m x 0.25 mm x 0.25 μm)

Injector-Port Type: Capillary

Injector-Port Temp: 250 ˚C

Injection Type: Split (20 mL/min)

Syringe Volume: 5 μL

Injection Volume: 0.5 μL

Injection Speed: Fast

Rinse Solvent: Methanol

Carrier-Gas Program: 1 mL/min

Oven Program: Temperature Hold Time Rate

80 ˚C 3 min 5 ˚C/min

140 ˚C 0 min 45 ˚C/min

275 ˚C Hold

Table 2. Operation Specifications for MS.

Mass Spectrometer: PerkinElmer Clarus 560 D MS

GC Inlet Temp: 250 ˚C

Ion-Source Temp: 250 ˚C

Function Type: Full Scan

Full-Scan Range: m/z 40-300

Full-Scan Time: 0.15 sec

Interscan Delay: 0.05 sec

Solvent Delay: 2.5 min

Experimental

External Calibration Curve

A limonene standard (SPEX CertiPrep®, Metuchen, NJ) with a concentration of 1000 µg/mL was diluted to 100 µg/mL by a 10:1 dilution with methanol. The remaining solutions were prepared by serial 2:1 dilutions resulting in final limonene concentrations of 50, 25, 12.5, and 6.25 µg/mL.

Extraction of limonene

Samples of lemon, orange, and grapefruit rinds were carefully collected using a razor blade. The samples were checked to ensure that none of the white flesh under the rind was included in the sample, as shown in Figures 2 and 3. The white flesh contributes to the mass of the sample but contains little limonene; this makes the rinds appear to have a lower limonene concentration. Then each sample was cut down to a mass of approximately 0.1 g. The rind samples were each placed in 7 mL vials with 5 mL of methanol. The vials were shaken vigorously for 5 minutes and then allowed to stand for an additional 5 minutes. After the 10-minute extraction was complete, 0.5-mL aliquots of methanol from each vial were diluted volumetrically (20:1 for lemon and grapefruit rinds, and 10:1 for orange rind). These dilutions were necessary in order to prepare solutions with concentra-tions of analyte within the range of the previously prepared calibration curve.

Analysis and quantification of limonene

The analysis of the standards and samples was performed with a PerkinElmer® Clarus® 560 D GC/MS, using the parameters shown in Table 1. The GC was fitted with a capillary injector port using a 4-mm standard glass liner packed with quartz wool configured for split operation (PerkinElmer Part No. N6121010). A PerkinElmer Elite™-5ms (30 m x 0.25 mm x 0.25 µm) column (PerkinElmer Part No. N9316282) was used throughout; the details of the method are shown in Tables 1 and 2.

Figure 2. Example of an orange rind being cut with a razor blade.

Figure 3. Example of a good sample of orange rind. (None of the white flesh is on the sample).

3

Table 3. Intermediate and Final Results for the Analysis of Lemon, Grapefruit and Orange Rinds.

Diluted Undiluted Mass Mass of Conc. Conc. Extracted Sample % (µg/mL) (µg/mL) (µg) (g) wt/wt

Lemon 35.66 713.2 3566 0.1199 2.97

Grapefruit 44.55 891.0 4455 0.1557 2.86

Orange 35.62 356.2 1781 0.1096 1.63

Conclusion

This application note demonstrates a simple extraction and quantification method for limonene using GC/MS. The limonene extraction and calibration curve preparation were discussed, as well as the method for analysis. The results obtained by following this method were presented along with the final %wt/wt of oil in the rinds. It was discovered that while all of these fruits had limonene in their rinds, lemon contained the highest concentration. Students con-ducting this analysis will gain valuable experience in sample preparation, solid-liquid extractions, and one of the most sensitive analytical techniques for the analysis of volatile compounds.

Discussion

Mass spectra for the limonene standard and limonene in the extract are shown in Figure 4. The limonene spectrum and retention time in the standard matched those of the fruit extract, and a NIST library search also supported the iden-tification as limonene. The chromatogram for m/z 136 was chosen for quantification because it is a unique, high m/z peak that is relatively abundant; higher m/z peaks generally experience a better signal-to-noise ratio.

The extracted m/z 136 ion chromatogram for the orange sample is shown in Figure 5. The amount of limonene in each sample was quantified by plotting a calibration curve using the instrument response at m/z 136, shown in Figure 6. The linear regression analysis of the calibration curve in Figure 6 yielded Equation 1, which was used to calculate the concentration of limonene in the sample. These concen-trations were then used to calculate the concentrations of the undiluted solutions, which were then used to determine the wt/wt % of limonene in each fruit’s rind; these results are shown in Table 3.

Equation 1: y = 941.4172x + 2317.1604

Figure 5. The extracted ion chromatogram for the 100 μg/mL limonene standard (top) and the diluted orange extract (bottom) at m/z 136.

Figure 6. Calibration curve of limonene used to quantify the samples.

Figure 4. Mass spectrum for limonene in the rind extract (top) and in the standard (bottom).




References

1. Limonene. R.E.D. Facts. 1994. USA EPA: http://www.epa.gov/oppsrrd1/REDs/factsheets/3083fact.pdf

2. Crowell PL, Gould MN. “Chemoprevention and therapy of cancer by d-limonene.” 1994 Crit Rev Oncog.; 5(1):1-22

3. Cyclone Power Technologies Inc. Why It’s Better 2009. http://www.cyclonepower.com/better.html

4. Orange Oil: http://en.wikipedia.org/wiki/Orange_oil

Introduction

Hydrochloric acid (HCl) is widely used in the semiconductor industry. Semiconductor devices are currently being designed with smaller line widths and are more susceptible to low-level impurities. In more critical processes, the impurities in HCl need to be monitored for continuous performance at desired and achievable levels of quality. SEMI Standard C27-07081 specifies the maximum con-taminant levels for each metal ranging from ppt to 0.1 ppm depending upon the grade or tier.

ICP-Mass Spectrometry

a p p l i c a t i o n B R i E F

Authors

Jianmin Chen, Ph.D.

Wilson You


Analysis of Impurities in Semiconductor Grade Hydrochloric Acid by Dynamic Reaction Cell ICP-MS

2

The Dynamic Reaction Cell (DRC™) is another technique which uses a quadrupole mass filter where both RF and DC voltages can be applied. The advantage of this configura-tion is that ions of a specific mass range pass through the cell, while ions outside of this range are ejected from the cell. This process is known as Dynamic Bandpass Tuning (DBT). As a result of this capability, undesirable by-product ions do not form within the cell, even when very reactive gases are used, such as NH3 and O2.

This application demonstrates the DRC’s ability to easily remove interferences so that trace levels of impurities in HCl can be measured using hot plasma conditions for all analytes during a single analysis.

Experimental conditions

Twenty percent HCl (Tamapure-AA 100, TAMA Chemicals, Japan) was analyzed directly without any sample preparation or dilution. Standard solutions were made from a 10 mg/L multi-element standard (PerkinElmer Pure, PerkinElmer, Inc., Shelton, CT USA).

The instrumentation used for this experiment was an ELAN® DRC II (PerkinElmer, Shelton, CT). Instrumental parameters and sample introduction components are shown in Table 1.

Inductively coupled plasma mass spectrometry (ICP-MS) traditionally has been an indispensable analytical tool for quality control because of its ability to rapidly determine analytes simultaneously at the ultratrace (ng/L or parts-per-trillion) level in various process chemicals. However, it should be pointed out that under conventional plasma conditions, argon ions combine with matrix components to generate polyatomic interferences. Some of the chloride-based inter-ferences observed during the analysis of HCl are 37Cl1H2 on 39K, 35Cl16O on 51V, 35Cl16O1H on 52Cr, 37Cl16O on 53Cr, 37Cl16O16O on 69Ga, 40Ar35Cl on 75As.

While cold plasma has been shown to be effective in reducing argon based interferences, it is even more prone to matrix suppression than hot plasma. Additionally, because of the low plasma energy, other polyatomic interferences which are not seen under hot plasma conditions may be preferentially formed. Collision cells using multipoles and low reactive gases have proven useful in reducing polyatomic interferences. This approach necessitates the use of kinetic energy dis-crimination to remove the unwanted by-products. However kinetic energy discrimination results in the loss of sensitivity, which is an issue when analyzing ng/L levels. Additionally, sensitivity loss is more significant for lighter analytes.

Table 1. Instrumental parameters and sample introduction components for ELAN DRC II ICP-MS.

Spray chamber Quartz Nebulizer PFA-100

Torch Quartz-High efficiency Plasma gas 16 L/min

Torch injector Pt Auxiliary gas 1.5 L/min

Sampler cone Pt RF power 1600 W

Skimmer cone Pt Integration time 1 sec/mass

Figure 1. Four hour long-term stability at 100 ng/L spiked level in 20% HCl. Both DRC and standard condition elements were determined in the same multi-element run with the total measurement time less than 4 minutes per sample.


Copyright ©2009-2011, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners. 008757A_01


Table 2. DLs and BECs, spike recoveries at 25 ng/L level and 4 hr long-term stability

results at 100 ng/L level for all analytes in 20% HCl.

BEC DL Recovery Stability

Analytes m/z Mode ng/L ng/L % %

Li 7 Standard 0.7 0.1 102 2.2

Be 9 Standard 2.5 1.5 103 3.2

B 11 Standard 6.3 4.1 117 2.5

Na 23 Standard 0.7 0.4 102 1.8

Mg 24 Standard N.D. 0.5 101 1.9

Al 27 DRC 2.0 1.2 115 4.5

K 39 DRC 20.6 4.9 109 4.3

Ca 40 DRC 2.5 1.0 106 3.3

Ti 48 DRC 4.7 3.0 97 6.6

V 51 DRC N.D. 10.0 112 5.9

Cr 52 DRC 3.6 2.8 105 4.7

Mn 55 DRC 1.7 0.6 98 2.5

Fe 56 DRC 13.2 2.1 96 1.8

Co 59 DRC 1.1 0.3 111 4.3

Ni 60 DRC 5.3 0.8 114 4.0

Cu 63 DRC 5.3 2.2 109 4.5

Zn 66 DRC 10.1 1.7 118 3.0

Ga 69 DRC 2.6 1.1 102 2.6

Ge 74 Standard 3.3 1.5 91 3.5

Sr 88 Standard 2.5 1.4 109 2.2

AsO 91 DRC 7.2 2.6 89 3.2

SeO 96 DRC 6.1 2.6 92 5.2

Mo 98 Standard 1.8 0.9 103 2.0

Ag 107 Standard 0.6 0.4 102 1.7

Cd 111 Standard 1.8 1.3 101 2.0

Sn 120 Standard 1.8 1.0 112 1.4

Sb 121 Standard 1.5 0.3 121 1.3

Ba 138 Standard 0.3 0.2 106 1.6

Au 197 Standard 1.2 0.9 113 1.7

Pb 208 DRC 0.2 0.1 109 3.8

Results

20% HCl samples were quantitatively analyzed using the method of additions calibrations; results are summarized in Table 2. The Detection Limits (DLs) were calculated by three times the standard deviation of 20% HCl and accounting for analytes sensitivity in 20% HCl. The Background Equivalent Concentrations (BECs) were calculated by measuring the signal intensities of 20% HCl and considering the analytes sensitivities in 20% HCl. For the spike recoveries, values were calculated at 25 ng/L level, and the four hour long-term stability results were obtained at 100 ng/L level. Figure 1 clearly shows good data quality over time which highlights the accuracy of ELAN DRC II ICP-MS for the determination of all SEMI required elements in HCl matrix.

Conclusion

The ELAN DRC II ICP-MS is shown to be robust and suitable for the routine quantifica-tion of ultratrace impurities at the ng/L level in 20% HCl. By means of computer controlled switching between standard mode and DRC mode, interference-free analysis using hot plasma conditions for all analytes was possible during a single sample run.

Reference

1. SEMI Standard C27-0708, SEMI Standards, http://www.semi.org/en/index.htm

N.D. = Not Detected; Standard = Standard mode; DRC = DRC mode.

Introduction

Ultrapure Water (UPW) is used for the cleaning of instru-ments and containers in trace analysis and for dilution of samples. The analysis of impurities in UPW requires increasingly lower levels of detection and higher instru-ment productivity. SEMI Standard F63-03091 specifies a maximum contamination for metals of 0.02-0.1 ppb for each element for ultrapure water used in semiconductor processing.



Authors

Jianmin Chen, Ph.D.

Wilson You


Analysis of Impurities in Ultrapure Water by Dynamic Reaction Cell ICP-MS

2

The Dynamic Reaction Cell (DRC™) is another technique which uses a quadrupole mass filter where both RF and DC voltage can be applied. The advantage of this configuration is that ions of a specific mass range pass through the cell, while ions outside of this range are ejected from the cell. This process is known as Dynamic Bandpass Tuning (DBT). As a result of this capability, undesirable by-product ions do not form within the cell, even when very reactive gases are used, such as NH3 and O2.

This application demonstrates the DRC’s ability to easily remove interferences so that trace levels of impurities in UPW can be measured using hot plasma conditions for all analytes during a single analysis.


It is recommended to add small amount of HNO3 (about 1%) to stabilize the analytes in the samples and to avoid absorption of the analytes onto the sample tubing. Standard solutions were made from a 10 mg/L multi-element standard (PerkinElmer Pure, PerkinElmer, Inc., Shelton, CT, USA).

The instrumentation used for this experiment was an ELAN® DRC™ II (PerkinElmer, Shelton, CT). Instrumental parameters and sample introduction components are shown in Table 1.

Inductively coupled plasma mass spectrometry (ICP-MS) traditionally has been an indispensable analytical tool for a useful quality control because of its ability to rapidly determine analytes simultaneously at the ultratrace (ng/L or parts-per-trillion) level in various process chemicals. However, it should be pointed out that under conventional plasma conditions, argon ions combine with matrix com-ponents to generate polyatomic interferences. Some of the common interferences are 38Ar1H on 39K, 40Ar on 40Ca, 40Ar16O on 56Fe.

While cold plasma has been shown to be effective in reducing argon based interferences, it is even more prone to matrix suppression than hot plasma. Additionally, because of the low plasma energy, other polyatomic interferences which are not seen under hot plasma conditions, may be preferentially formed. Collision cells using multipoles and low reactive gases have proven useful in reducing polyatomic interferences. This approach necessitates the use of kinetic energy dis-crimination to remove the unwanted by-products. However kinetic energy discrimination results in the loss of sensitivity, which is an issue when analyzing ng/L levels. Additionally, sensitivity loss is more significant for lighter analytes.







Figure 1. A four hour long-term stability analysis for all analytes spiked at 100 ng/L in UPW. Both DRC and standard condition elements were determined in the same multi-element run with the total measurement time less than 4 minutes per sample.




Table 2. DLs and BECs, spike recoveries at 10 ng/L level and 4 hr long-term stability

results at 100 ng/L level for all analytes in UPW.



Li 7 Standard 0.7 0.1 93 1.1

Be 9 Standard 4.4 1.3 98 1.6

B 11 Standard 8.5 2.2 114 1.4

Na 23 Standard N.D. 0.06 95 1.4

Mg 24 Standard 0.3 0.2 95 1.7

Al 27 DRC 0.3 0.1 103 2.7

K 39 DRC 2.9 0.2 105 2.1

Ca 40 DRC 0.5 0.2 99 2.6

Ti 48 DRC 0.7 0.7 108 3.6

V 51 DRC 0.9 0.3 97 3.6

Cr 52 DRC 0.9 0.2 102 2.5

Mn 55 DRC 0.4 0.6 101 2.9

Fe 56 DRC 1.4 0.3 102 2.7

Co 59 DRC 0.10 0.04 103 2.2

Ni 60 DRC 0.7 0.1 102 3.7

Cu 65 DRC 0.7 0.1 103 2.1

Zn 66 DRC 1.4 0.5 91 2.0

Ga 69 Standard N.D. 0.8 96 1.6

Ge 74 Standard N.D. 0.6 99 3.4

As 75 Standard 2.0 1.6 97 3.5

Sr 88 Standard 0.06 0.01 99 1.8

Mo 95 Standard N.D. 0.15 97 1.8

Ag 109 Standard 0.15 0.11 99 1.6

Cd 114 Standard 0.22 0.03 95 1.1

In 115 Standard N.D. 0.10 98 1.7

Sn 118 Standard 0.28 0.02 98 3.8

Sb 121 Standard 0.18 0.06 95 2.8

Ba 138 Standard 0.08 0.07 94 1.8

W 184 Standard 0.15 0.07 95 1.5

Au 197 Standard 0.15 0.15 99 1.8

Tl 205 Standard 0.06 0.04 96 1.4

Pb 208 DRC N.D. 0.04 102 1.9

Bi 209 Standard N.D. 0.02 97 1.9

Results

UPW samples were quantitatively analyzed using the method of additions calibrations results are summarized in Table 2. The Detection Limits (DLs) were calculated by three times the standard deviation of UPW and accounting for analytes sensitivity in UPW. The Background Equivalent Concentrations (BECs) were calculated by measuring the signal intensities and considering the analytes sensitivities in UPW. For the spike recoveries, values were calculated at 10 ng/L level, and the four hour long-term stability result were obtained at 100 ng/L level. Figure 1 clearly shows the good data quality over time which highlights the accuracy of ELAN DRC II ICP-MS for the determination of all SEMI required elements in UPW.

Conclusion

The ELAN DRC II ICP-MS is shown to be robust and suitable for the routine quantifica-tion of ultratrace impurities at the ng/L level in UPW. By means of computer controlled switching between standard mode and DRC mode, interference-free analysis using hot plasma conditions for all analytes was possible during a single sample run.

Reference

1. SEMI Standard F63-0309, SEMI Standards, http://www.semi.org/en/index.htm

N.D. = Not Detected; Standard = Standard mode; DRC = DRC mode.

Introduction

Tetramethylammonium hydroxide (TMAH) is a clear, water-soluble, strongly alkaline organic solvent which is widely used as a developer in the photolithography process for semiconductor and Liquid Crystal Display (LCD) manufacturing. Because of its wide use, the analysis of impurities in TMAHs becomes more critical in these demanding applications. SEMI Standard C46-03061 specifies limits for 25% TMAH, generally limiting contamination to less than 10 ppb for each element, although some users may require lower levels of impurities.



Authors

Jianmin Chen, Ph.D.

Wilson You


Analysis of Semiconductor Grade TMAH by Dynamic Reaction Cell ICP-MS

2

The Dynamic Reaction Cell (DRC™) is another technique which uses a quadrupole mass filter where both RF and DC voltages can be applied. The advantage of this configuration is that ions of a specific mass range pass through the cell, while ions outside of this range are ejected from the cell. This process is known as Dynamic Bandpass Tuning (DBT). As a result of this capability, undesirable by-product ions do not form within the cell, even when very reactive gases are used, such as NH3 and O2.

This application demonstrates the DRC’s ability to easily remove interferences so that trace levels of impurities in TMAH can be measured using hot plasma conditions for all analytes during a single analysis.


Normally the concentration of TMAH is about 25%, and sample preparation consisted of a five-fold dilution with pure water, resulting in a 5% (W/W) solution. Standard solutions were made from a 10 mg/L multi-element standard (PerkinElmer Pure, PerkinElmer, Inc., Shelton, CT USA).


Inductively coupled plasma mass spectrometry (ICP-MS) traditionally has been an indispensable analytical tool for useful quality control because of its ability to rapidly determine analytes simultaneously at the ultratrace (ng/L or parts-per-trillion) level in various process chemicals. However, it is extremely important to address the significant matrix-derived polyatomic interferences which form, as well as matrix suppression effects due to carbon content. These issues arise when analyzing organic solvents directly.

While cold plasma has been shown to be effective in reducing argon based interferences, it is even more prone to matrix suppression than hot plasma. Additionally, because of the low plasma energy, other polyatomic interferences which are not seen under hot plasma conditions, may be preferentially formed. Collision cells using multipoles and low reactive gases have proven useful in reducing polyatomic interferences. This approach necessitates the use of kinetic energy discrim-ination to remove the unwanted by-products. However kinetic energy discrimination results in the loss of sensitivity, which is an issue when analyzing ng/L levels. Additionally, sensitivity loss is more significant for lighter analytes.







Figure 1. A four hour long-term stability test of 200 ng/L spikes in 5% TMAH. Sample was continuously introduced without rinse and both DRC and standard condition elements were determined in the same multielement run with the total measuring time less than 4 minutes per sample.




Table 2. DLs, BECs, Spike recoveries and 4 hr long-term stability test at 200 ng/L level

for all analytes in 5% TMAH.



Li 7 Standard 1.0 0.4 112 1.8

B 11 Standard 50.7 8.9 92 1.9

Na 23 Standard 7.4 1.3 102 2.0

Mg 24 DRC 9.8 4.1 93 4.5

Al 27 DRC 1.8 2.6 103 3.9

K 39 DRC 21.2 3.6 107 3.5

Ca 40 DRC 3.3 1.3 93 4.7

Ti 48 DRC 2.0 0.9 106 5.0

V 51 DRC 5.0 0.9 94 4.7

Cr 52 DRC 4.9 1.7 103 4.3

Mn 55 DRC 1.8 0.6 98 3.4

Fe 56 DRC 13.7 1.0 113 3.1

Co 59 DRC 6.7 2.7 106 3.7

Ni 60 DRC 32.3 1.9 100 4.4

Cu 63 DRC 7.3 0.6 113 4.4

Zn 64 DRC 3.7 1.8 96 2.9

As 75 Standard 1.3 0.3 114 3.6

Se 82 Standard 15.7 5.0 108 3.1

Sr 88 Standard 2.5 0.2 95 1.9

Mo 95 Standard 3.8 1.5 96 2.4

Ag 107 Standard 2.2 0.7 82 3.6

Cd 112 Standard 1.2 0.6 92 2.3

Sn 118 Standard 9.2 0.7 91 1.5

Sb 121 Standard 8.9 0.8 92 3.8

Ba 138 Standard 1.1 0.4 107 1.5

Pb 208 DRC 0.1 0.1 93 3.5

Results

TMAH samples were quantitatively analyzed using the method of additions calibrations; results are summarized in Table 2. The Detection Limits (DLs) were calculated by three times the standard deviation of 5% TMAH and accounting for analytes sensitivity in 5% TMAH. The Background Equivalent Concentrations (BECs) were calculated by measuring the signal intensities in 5% TMAH and considering the analyte sensitivities in 5% TMAH. For the four hour long-term stability test, 200 ng/L spikes in 5% TMAH were continuously introduced without rinse, and Figure 1 clearly showed the good data quality over time, which highlights the accuracy of ELAN DRC II ICP-MS for the determination of

all SEMI required elements in TMAH matrix.

Conclusion

The ELAN DRC II ICP-MS is shown to be robust and suitable for the routine quantifica-tion of ultratrace impurities at the ng/L level in UPW. By means of computer controlled switching between standard mode and DRC mode, interference-free analysis using hot plasma conditions for all analytes was possible during a single sample run.

Reference

1. SEMI Standard C46-0306, Guideline for Tetramethylammonium hydroxide, available from http://www.semi.org/en/index.htm

Introduction

Nitric acid (HNO3) is widely used in the semiconductor industry. Semiconductor devices are currently being designed with smaller line widths and are more susceptible to low level impurities. In more critical processes, the impurities in HNO3 need to be monitored for continuous performance at desired and achievable levels of quality. SEMI Standard C35-07081 specifies the maximum concentration of metal contaminants by element and tier for nitric acid.



Authors

Jianmin Chen, Ph.D.

Wilson You


Analysis of Impurities in Nitric Acid by Dynamic Reaction Cell ICP-MS

2

The Dynamic Reaction Cell (DRC™) is another correction technique which uses a quadrupole mass filter where both RF and DC voltage can be applied. The advantage of this configuration is that ions of a specific mass range pass through the cell, while ions outside of this range are ejected from the cell. This process is known as Dynamic Bandpass Tuning (DBT). As a result of this capability, undesirable by-products ions do not form within the cell, even when very reactive gases are used, such as NH3 and O2.

This application demonstrates the DRC’s ability to easily remove interferences so that trace levels of impurities in HNO3 can be measured using hot plasma conditions for all analytes during a single analysis.


Normally the concentration of HNO3 is around 70%, and at least a two-fold dilution is recommended (Tamapure-AA 10, TAMA Chemicals, Japan). Standard solutions were made from a 10 mg/L multi-element standard (PerkinElmer Pure, PerkinElmer, Inc., Shelton, CT USA).


Inductively coupled plasma mass spectrometry (ICP-MS) traditionally has been an indispensable analytical tool for quality control because of its ability to rapidly determine analytes simultaneously at the ultratrace (ng/L or parts-per-trillion) level in various process chemicals. However, it should be pointed out that under conventional plasma conditions, argon ions combine with matrix components to generate polyatomic interferences. Some of the common interfer-ences are 38Ar1H on 39K, 40Ar on 40Ca, 40Ar16O on 56Fe.

While cold plasma has been shown to be effective in reducing argon-based interferences, it is even more prone to matrix suppression than hot plasma. Additionally, because of the low plasma energy, other polyatomic interferences which are not seen under hot plasma conditions, may be preferentially formed. Collision cells using multipoles and low reactive gases have proven useful in reducing polyatomic interferences. This approach necessitates the use of kinetic energy discrimination to remove the unwanted by-products. However, kinetic energy discrimination results in the loss of sensitivity, which is an issue when analyzing ng/L levels. Additionally, sensitivity loss is more significant for lighter analytes.







Figure 1. A four hour long-term stability test at 100 ng/L spike for selected analytes in 28% HNO3. Both DRC and standard condition elements were determined in the same multi-element run with the total measuring time less than 4 minutes per sample.




Table 2. DLs and BECs for all analytes in 10% HNO3, spike recoveries at 10 ng/L level

and 4 hr long-term stability results at 100 ng/L level for all analytes in 28% HNO3.

BEC DL Recovery Stability Analytes m/z Mode ng/L ng/L % %

Li 7 Standard 0.9 0.4 114 2.7

Be 9 Standard 1.2 0.2 103 2.8

B 11 Standard 39.6 2.6 92 2.9

Na 23 Standard 0.8 0.1 105 2.1

Mg 24 Standard 0.5 0.4 104 1.9

Al 27 DRC 0.7 0.2 103 3.7

K 39 DRC 6.8 0.1 109 2.5

Ca 40 DRC 3.4 0.8 112 2.6

Ti 48 DRC 3.7 0.4 97 4.4

V 51 DRC 0.8 0.2 103 1.7

Cr 52 DRC 1.9 0.3 104 2.4

Mn 55 DRC 0.4 0.1 102 2.1

Fe 56 DRC 2.8 0.4 101 1.7

Co 59 DRC 0.1 0.1 95 2.1

Ni 60 DRC 1.4 1.0 102 2.8

Cu 65 DRC 4.0 0.4 104 2.1

Zn 66 DRC 2.2 0.8 97 2.3

Ga 69 Standard 3.7 0.4 105 1.8

Ge 74 Standard 2.1 0.7 98 1.6

As 75 Standard 9.9 2.9 102 1.5

Sr 88 Standard 0.3 0.2 104 0.9

Mo 95 Standard 1.8 0.4 101 1.4

Ag 109 Standard 1.0 0.2 102 0.8

Cd 114 Standard 0.16 0.02 100 0.8

In 115 Standard 0.18 0.02 101 0.7

Sn 118 Standard 1.4 0.3 99 1.0

Sb 121 Standard 0.3 0.2 99 1.0

Ba 138 Standard 0.3 0.2 103 0.9

W 184 Standard 0.13 0.04 102 1.0

Au 197 Standard 0.23 0.04 101 1.3

Tl 205 Standard 0.08 0.15 104 1.3

Pb 208 DRC 0.12 0.09 102 1.8

Bi 209 Standard 0.09 0.09 104 1.4

Results

HNO3 samples were quantitatively analyzed using the method of additions calibrations; results are summarized in Table 2. The Detection Limits (DLs) were calculated by three times the standard deviation of 10% HNO3 and accounting for analytes sensitivity in 10% HNO3. The Background Equivalent Concentrations (BECs) were calculated by measuring the signal intensities in 10% HNO3 and considering the analytes sensitivi-ties in 10% HNO3. For the spike recoveries, values were calculated at 10 ng/L level in 28% HNO3. In addition, 100 ng/L spikes also in 28% HNO3 were continuously introduced without rinse to generate the four hour long-term stability result, and Figure 1 shows the good data quality over time which highlights the accuracy of ELAN DRC II ICP-MS for the determination of all SEMI-required elements in HNO3 matrix.

Conclusion

The ELAN DRC II ICP-MS is shown to be robust and suitable for the routine quantification of ultratrace impurities at the ng/L level in HNO3. By means of computer controlled switching between standard mode and DRC mode, interference-free analysis using hot plasma conditions for all analytes was possible during a single sample run taking less than 4 minutes.

Reference

1. SEMI Standard C35-0708, SEMI Standards, http://www.semi.org/en/index.htm

Standard = Standard mode; DRC = DRC mode.

PerkinElmer, Inc.940 Winter StreetWaltham, MA 02451 USAP: (800) 762-4000 or(+1) 203-925-4602www.perkinelmer.com


Copyright ©2009, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners.

008861B_02

USEFUL LINKS

Access our application archives

By Industry:

• Consumer Product Safety• Environmental• Food, Flavors and Agricultural Analysis• Forensic Analysis• Petrochemical Analysis• Pharmaceutical Development & Manufacturing• Polymers• Renewable Energy• Semiconductor & Electronics

By Technology:

• Atomic Absorption (AA)• Elemental Analysis• Gas Chromatography (GC)• GC Mass Spectrometry (GC/MS)• ICP Mass Spectrometry (ICP-MS)• Inductively Coupled Plasma (ICP-OES & ICP-AES)• Infrared Spectroscopy (FT-IR & IR)• LIMS & Data Handling• Liquid Chromatography (HPLC & UHPLC)• Mass Spectrometry• Raman Spectroscopy• Thermal Analysis• UV/Vis & UV/Vis/NIR

Sign Up Now!

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=Atomic+Absorption+%5bAA%5d

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=Elemental+Analysis

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=Gas+Chromatography%2fMass+Spectrometry

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=Gas+Chromatography

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=ICP+Optical+Emission+%5bICP-OES%5d

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=ICP-Mass+Spectrometry

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=LIMS+%2f+Software

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=FTIR+%26+FTNIR+Spectrometers

http://las.perkinelmer.com/Catalog/FamilyPage.htm?CategoryID=Raman+Spectrometers

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=Mass+Spectrometry+%5bGC%2fMS+and+ICP-MS%5d

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=Liquid+Chromatography+HPLC+and+UHPLC

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=UV%2fVis+Spectrophotometers

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=Thermal+Analysis

http://web2.perkinelmer.com/?elqPURLPage=610

http://www.perkinelmer.com/Industries/Consumer_Products_Manufacturing/cat1/NAV_03_IND_Industries_002/cat2/NAV_IND_Consumer%20Products%20-%20Manufacturing_006

http://www.perkinelmer.com/Industries/Environmental/cat1/NAV_03_IND_Industries_002/cat2/NAV_IND_Environmental_010

http://www.perkinelmer.com/Industries/Food-Beverage-Nutraceuticals/cat1/NAV_03_IND_Industries_002/cat2/NAV_IND_Food%20and%20Beverage%20Nutraceuticals_014

http://www.perkinelmer.com/Industries/Forensics/cat1/NAV_03_IND_Industries_002/cat2/NAV_IND_Forensics_018

http://las.perkinelmer.com/FocusAreas/Mkt+Petrochemical+Analysis/Default.htm

http://www.perkinelmer.com/Industries/Pharmaceutical-Biotechnology/cat1/NAV_03_IND_Industries_002/cat2/NAV_IND_Pharmaceutical%20and%20Biotechnology_048

http://las.perkinelmer.com/Catalog/CategoryPage.htm?CategoryID=Polymers+and+Plastics

http://las.perkinelmer.com/FocusAreas/Mkt+Sustainable+Energy/Default.htm

http://las.perkinelmer.com/Catalog/Mkt.htm?CategoryID=Mkt+Semiconductor+Electronics

Spotlight on Analytical Applications Complete e-Zine Vol. 1

Technology

release of formaldehyde

formaldehyde resinsare

formaldehyde stock solution

high level of formaldehyde

method of analysis

applications ezine volume

determination ofisoflavones

standard solution