www.flowinjection.com Page | 1 Trace-Level Iron Determination – FIA-120 PRINCIPLE This method is designed for the determination of iron in water. The sample is prepared offline to ensure that all iron is present in trivalent form and then introduced to the FIAlab analyzer. A chelating resin is used for in-line preconcentration of iron, followed by elution with acid. Iron generates a chemiluminescence signal when mixed with luminol and hydrogen peroxide. This method is designed to be run on the FIAlyzer-1000. SUMMARY This method is designed for the determination of iron in water. The method is capable of detecting iron in the range of 1-20 nmol / L. Note: range is highly dependent on preconcentration time. For more information, see the section on performance metrics. SAFETY The toxicity or carcinogenicity of all reagents used in this method must be taken into account and therefore each chemical listed below should be handled accordingly. Each laboratory is responsible for maintaining compliance with OSHA regulations regarding the safe handling of the chemicals specified in this method. Material Safety Data Sheets (MSDS) should be made available to all personnel using the method. All waste materials should be disposed of in a responsible manner, in accordance with federal, state, local, and any other applicable regulations. The following chemicals have the potential to be highly toxic or highly hazardous; for detailed explanations consult the MSDS: o Hydrogen peroxide o Hydrochloric acid o Acetic acid o Ammonia o Triethylenetetramine Method for Iron Determination by Luminol, Version 2.1
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Method for Iron Determination by Luminol, Version 2...Trace-Level Iron Determination – FIA-120 PRINCIPLE This method is designed for the determination of iron in water. The sample
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Page | 1
Trace-Level Iron Determination – FIA-120
PRINCIPLE
This method is designed for the determination of iron in water. The sample is prepared offline to ensure
that all iron is present in trivalent form and then introduced to the FIAlab analyzer. A chelating resin is
used for in-line preconcentration of iron, followed by elution with acid. Iron generates a
chemiluminescence signal when mixed with luminol and hydrogen peroxide.
This method is designed to be run on the FIAlyzer-1000.
SUMMARY
This method is designed for the determination of iron in water. The method is capable of detecting iron
in the range of 1-20 nmol / L. Note: range is highly dependent on preconcentration time. For more
information, see the section on performance metrics.
SAFETY
The toxicity or carcinogenicity of all reagents used in this method must be taken into account and
therefore each chemical listed below should be handled accordingly.
Each laboratory is responsible for maintaining compliance with OSHA regulations regarding the safe
handling of the chemicals specified in this method. Material Safety Data Sheets (MSDS) should be made
available to all personnel using the method.
All waste materials should be disposed of in a responsible manner, in accordance with federal, state,
local, and any other applicable regulations.
The following chemicals have the potential to be highly toxic or highly hazardous; for detailed
explanations consult the MSDS:
o Hydrogen peroxide o Hydrochloric acid o Acetic acid o Ammonia o Triethylenetetramine
Method for Iron Determination by Luminol, Version 2.1
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Trace-Level Iron Determination – FIA-120
EQUIPMENT AND SUPPLIES
Equipment: o Balance, analytical, with a 0.01 g resolution o Pipettes for making standards
Glassware: o Acid-cleaned PP (polypropylene) volumetric flasks or measuring cylinders. o Pipettors with plastic trace metal clean tips o Acid-cleaned LDPE (low density polyethylene) or PP (polypropylene) storage containers o Note: acid cleaning = soak in ~1 M trace metal grade HCl for at least 7 days. Then rinse
with copious amounts of deionized water.
Autosampler (for high sample loads):
o Cetac ASX-280/560 (recommended) or AIM-3200/3300
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Trace-Level Iron Determination – FIA-120
REAGENTS AND STANDARDS
Chemical part numbers refer to Sigma-Aldrich unless noted otherwise. Note: (T) = TOSOH Bioscience PN
a For ultralow-level work, deionized water should be purified further with polishing cartridges for metal removal.
b For lowest level detection, it is recommended that ammonium hydroxide is purified by distillation (isothermal or elevated temperature). c For lowest level detection, it is recommended that acetic acid is purified by distillation (isothermal or elevated temperature). d For lowest level detection, it is recommended that hydrochloric acid is purified by distillation (isothermal or elevated temperature). Distillation is typically carried out after diluting HCl to ~6M strength.
Preparation of Reagents
o Carrier: 0.23 M hydrochloric acid (1L) □ Dilute 23mL of 30% hydrochloric acid to 1L with DI water.
o Luminol Stock Solution: 0.1M luminol (15mL)
□ Dissolve 0.27g of luminol together with 0.50g of sodium carbonate in 15mL of deionized water.
□ Keep shaking periodically until fully dissolved. □ Store in refrigerator. Prepare fresh weekly.
o Reagent 1: 0.24 mM luminol / 0.7 mM TETA solution (1 L)
□ Add 2.4mL of luminol stock solution and 40μL of TETA to 0.8L of deionized water.
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Trace-Level Iron Determination – FIA-120
□ Add deionized water to a total volume of 1L.
o Reagent 2: 0.44M ammonia (1 L) □ Add 30mL of 25% ammonia to 0.8L of deionized water. □ Add deionized water to a total volume of 1L.
Reagent 3: 0.3M hydrogen peroxide (1 L)
□ Add 30mL of 30% hydrogen peroxide to 0.8L of deionized water. □ Add deionized water to a total volume of 1L.
o Sample oxidation solution: 0.06% hydrogen peroxide (10mL)
□ Add 20 μL of 30% hydrogen peroxide to 10mL of deionized water.
o Sample buffer: 0.35M CH3COOH – 0.11M NH3, pH 4.5 (1L) □ Add 20mL of glacial acetic acid to 600mL of deionized water and mix. □ Add 7.6mL of 25% ammonia and mix. □ Add deionized water to a total volume of 1L.
o Probe Wash Solution: Water with 0.1% Brij L23 (1L)
□ Add 3.3mL Brij L23 to 800mL of deionized water, dilute to 1L. □ Mix well and store in a polyethylene bottle. □ The wash solution should be clear with no particles in it.
Notes on reagent shelf life:
o Use of high quality laboratory glass bottles is important. o Carrier should be prepared every month. o Luminol stock solution should be prepared every week. Store in refrigerator. o Reagent 1 should be prepared fresh daily. o Reagent 2 should be prepared every 3 months. o Reagent 3 should be prepared fresh daily. o Sample oxidation solution should be prepared fresh daily. o Sample buffer should be prepared fresh every month.
Preparation of Standards
o Dilute 1000 mg/L (18mM) Fe stock solution with deionized water to the desired range of iron standards.
o Acidify to pH ~ 1.8 by adding 1 part of 11 M HCl to 500 parts of standard solution (e.g. 120µL HCl to 60mL standard).
o Add 1 part of sample oxidation solution to 1000 parts standard solution (e.g. 60μL sample oxidation solution to 60mL standard).
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Trace-Level Iron Determination – FIA-120
SAMPLE COLLECTION AND PRETREATMENT
Sample collection and filtering depends on practices and apparatus in each individual laboratory
and is not described in this document.
Acidify filtered water samples to pH ~1.8 by adding 1 part of 11 M hydrochloric acid to 500 parts
of sample (e.g. 120µL HCl to 60mL sample).
One day before analysis, add 1 part of sample oxidation solution to 1000 parts sample (e.g. 60μL
sample oxidation solution to 60mL sample). This is to ensure that all iron is in the Fe(III) state.