APMP.QM-S5 Essential and Toxic Elements in Seafood Final Report Authors: Liliana Valiente (INTI) 1 , John W. Bennett (ANSTO) 2 , Rodrigo Caciano de Sena (INMETRO) 3 , Boriana Kotzeva (BIM) 4 , Gabriela Massiff (CMQ) 5 , Jingbo Chao and Jun Wang (NIM) 6 , Randa Nasr (NIS) 7 , Guillaume Labarraque (LNE) 8 , Elias Kakoulidis Eugenia Lampi (EIM) 9 , Della Wai-mei Sin, Chuen-shing Mok, Siu-kay Wong and Yiu-chung Yip (GLHK) 10 , Shankar Gopala Aggarwal Prabhat K. Gupta (NPLI) 11 , Yanbei Zhu and Shin-ichi Miyashita (NMIJ) 12 , Yong-Hyeon Yim (KRISS) 13 , Osman Zakaria (SIRIM) 14 , Judith Velina Lara Manzano (CENAM) 15 , Richard Shin (HSA) 16 , Milena Horvat (JSI) 17 , Charun Yafa (NIMT) 18 1 Instituto Nacional de technologia Industrial/Quimica, Argentina 2 Australian Nuclear Science and Technology Organisation, Australia 3 Instituto Nacional de Metrologia, Normalizacaoe Qualidade Industrial, Brazil 4 Bulgarian Institute of Metrology, National Centre of Metrology, Bulgaria 5 Chemical Metrology Center, Fundacion Chile 6 National Institute of Metrology, China 7 National Institute for Standards, Egypt 8 Laboratorie national de metrologie et d’essais, France 9 Hellenic Metrology Institute, EXHM, Greece 10 Government Laboratory, Hong Kong, China 11 CSIR-National Physical Laboratory, India 12 National Metrology Institute of Japan, Japan 13 Korean Research Institute of Standards & Science, Korea 14 National Metrology Laboratory, SIRIM BERHAD, Malaysia 15 Centro Nacional de Metrologia, Mexico 16 Health Sciences Authority, Singapore 17 Jozef Stefan Institute, Department of Environmental Sciences, Slovenia 18 National Institute of Metrology, Thailand
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APMP.QM-S5
Essential and Toxic Elements in Seafood
Final Report
Authors:
Liliana Valiente (INTI)1, John W. Bennett (ANSTO)
2, Rodrigo Caciano de Sena
(INMETRO)3, Boriana Kotzeva (BIM)
4, Gabriela Massiff (CMQ)
5, Jingbo Chao and Jun
Wang (NIM)6, Randa Nasr (NIS)
7, Guillaume Labarraque (LNE)
8, Elias Kakoulidis Eugenia
Lampi (EIM)9, Della Wai-mei Sin, Chuen-shing Mok, Siu-kay Wong and Yiu-chung Yip
(GLHK)10
, Shankar Gopala Aggarwal Prabhat K. Gupta (NPLI)11
, Yanbei Zhu and Shin-ichi Miyashita (NMIJ)
12, Yong-Hyeon Yim (KRISS)
13, Osman Zakaria (SIRIM)
14, Judith Velina
Lara Manzano (CENAM)15
, Richard Shin (HSA)16
, Milena Horvat (JSI)17
, Charun Yafa (NIMT)
18
1 Instituto Nacional de technologia Industrial/Quimica, Argentina
2 Australian Nuclear Science and Technology Organisation, Australia
3 Instituto Nacional de Metrologia, Normalizacaoe Qualidade Industrial, Brazil
4 Bulgarian Institute of Metrology, National Centre of Metrology, Bulgaria
5 Chemical Metrology Center, Fundacion Chile
6 National Institute of Metrology, China
7 National Institute for Standards, Egypt
8 Laboratorie national de metrologie et d’essais, France
9 Hellenic Metrology Institute, EXHM, Greece
10 Government Laboratory, Hong Kong, China
11 CSIR-National Physical Laboratory, India
12 National Metrology Institute of Japan, Japan
13 Korean Research Institute of Standards & Science, Korea
14 National Metrology Laboratory, SIRIM BERHAD, Malaysia
15 Centro Nacional de Metrologia, Mexico
16 Health Sciences Authority, Singapore
17 Jozef Stefan Institute, Department of Environmental Sciences, Slovenia
18 National Institute of Metrology, Thailand
Abstract
The Supplementary Comparison APMP.QM-S5 was undertaken to demonstrate the
capability of participating national metrology institutes (NMIs) and designated institutes
(DIs) in measuring the contents of the incurred essential elements (iron and zinc) and toxic
elements (total arsenic and cadmium) at g/g levels in a test sample of dried shrimp by
various analytical techniques.
At the APMP TCQM Meeting held in Pattaya, Thailand in November 2010, Government
Laboratory of the Government of the Hong Kong Special Administrative Region (GLHK)
proposed this APMP supplementary comparison. The proposal was further discussed and
agreed upon at the CCQM Inorganic Analysis Working Group Meeting held in Paris in April
2011. GLHK was the coordinating laboratory for the supplementary comparison. For
enhancing the collaboration amongst specialized regional bodies in Asia-Pacific and to help
build the laboratory capacity of NMIs/DIs from developing economies, the reference values
of the supplementary comparison are used for evaluation of performance of participants of
an APMP proficiency testing programme (APMP PT 11-01), an Asia-Pacific Laboratory
Accreditation Cooperation proficiency testing programme (APLAC T082) and an
Asia-Pacific Economic Co-operation proficiency testing programme (APEC PT), which
were concurrently run using the same testing material as in APMP.QM-S5.
The supplementary comparison serves to facilitate claims by participants on the Calibration
and Measurement Capabilities (CMCs) as listed in Appendix C of the Key Comparison
Database (KCDB) under the Mutual Recognition Arrangement of the International
Committee for Weights and Measures (CIPM MRA).
Totally 18 institutes registered for the supplementary comparison and all of them submitted
their results. Most of the participants used microwave acid digestion methods for sample
dissolution. For the instrumental determination, a variety of techniques like ICP-MS,
ICP-OES, INAA and AAS were employed by the participants. For this supplementary
comparison, inorganic core capabilities have been demonstrated by concerned participants
with respect to methods including ICP-MS (without isotope dilution), ID-ICP-MS, ICP-OES,
INAA and AAS on the determination of total arsenic, cadmium, iron and zinc in a matrix of
seafood.
Page 1 of 47
Table of Content
Page
1 Introduction 2
2 Participating Institutes 3
3 Samples and Instructions to Participants 4
3.1 Materials 4
3.2 Homogeneity and Stability Study 4
3.3 Instructions to Participants 6
4 Methods of Measurement 7
5 Results and Discussion 11
5.1 General 11
5.2 Calculation of reference mass fraction values and associated
uncertainties
16
5.3 Equivalence statements 23
6 Demonstration of Core Capabilities 32
7 Conclusion 32
Acknowledgement 33
References 33
Appendix 34
Page 2 of 47
1. Introduction
Food contamination with toxic elements is one of the major food safety issues in the
Asia-Pacific region. Most economies have laboratories that carry out routine analyses of
toxic elements in seafood for regulatory compliance and surveillance purposes.
Examinations of essential elements are performed for nutritional studies and quality
assurance.
The Asia-Pacific Metrology Programme (APMP) has been organizing inter-comparisons for
the purpose of establishing the technical basis for mutual recognition of measurement
capabilities among national metrology institutes (NMIs)/designated institutes (DIs) in the
Asia-Pacific region and worldwide. At the APMP TCQM Meeting held in Pattaya,
Thailand in November 2010, Government Laboratory of the Government of the Hong Kong
Special Administrative Region (GLHK) proposed an APMP supplementary comparison
(APMP.QM-S5) on the determination of essential elements (iron and zinc) and toxic
elements (total arsenic and cadmium) in a dried shrimp material. The proposal was further
discussed and agreed upon at the CCQM Inorganic Analysis Working Group Meeting held in
Paris in April 2011. For enhancing the collaboration amongst specialized regional bodies in
Asia-Pacific and to help build the laboratory capacity of NMIs/DIs from developing
economies, the reference values of the supplementary comparison would be used for
evaluation of performance of participants of an APMP proficiency testing programme
(APMP PT 11-01), an Asia-Pacific Laboratory Accreditation Cooperation proficiency testing
programme (APLAC T082) and an Asia-Pacific Economic Co-operation proficiency testing
programme (APEC PT), which are concurrently run using the same testing material as in
APMP.QM-S5. Dried shrimps are prepared by drying of seawater shrimps under the sun and
are commonly consumed to impart a characteristic flavour to many Asian cuisines. The
study is based on the analysis of naturally incurred materials. Its aim is to demonstrate the
capability of participating NMIs and DIs in measuring the contents of the incurred analytes
(iron, zinc, total arsenic and cadmium) at g/g levels in a test sample of dried shrimp by
various analytical techniques.
The supplementary comparison serves to facilitate claims by participants on the Calibration
and Measurement Capabilities (CMCs) as listed in Appendix C of the Key Comparison
Database (KCDB) under the Mutual Recognition Arrangement of the International
Committee for Weights and Measures (CIPM MRA). Participants are requested to complete
the Inorganic Core Capabilities Tables as a means of providing evidence for their CMC
claims.
Page 3 of 47
2. Participating Institutes
Totally 18 institutes registered for the Supplementary Comparison APMP.QM-S5. The list
showing the countries’ names of the participating NMIs/DIs in alphabetical order is given in
Table 1.
Table 1. List of participating NMIs/DIs for APMP.QM-S5
No. Institute Country Contact person
Results
submitted for
measurand
1
INTI
Instituto Nacional de technologia
Industrial/Quimica
Argentina Liliana Valiente As, Cd, Fe, Zn
2
ANSTO
Australian Nuclear Science and Technology
Organisation
Australia John W. Bennett As, Fe, Zn
3
INMETRO
Instituto Nacional de Metrologia,
Normalizacaoe Qualidade Industrial
Brazil Rodrigo Caciano
de Sena As, Cd, Fe, Zn
4
BIM
Bulgarian Institute of Metrology, National
Centre of Metrology
Bulgaria Boriana Kotzeva Zn
5 CMQ
Chemical Metrology Center, Fundacion Chile Chile Gabriela Massiff As, Cd, Fe, Zn
6 NIM
National Institute of Metrology, P.R. China China
Jingbo Chao
Jun Wang As, Cd, Fe, Zn
7 NIS
National Institute for Standards Egypt Randa Nasr As, Cd, Fe, Zn
8 LNE
Laboratorie national de metrologie et d’essais France
Guillaume
Labarraque As, Cd, Fe
9 EIM
Hellenic Metrology Institute, EXHM Greece
Elias Kakoulidis
Eugenia Lampi As, Cd, Fe, Zn
10 GLHK
Government Laboratory, Hong Kong, China
Hong Kong,
China Yiu-chung Yip As, Cd, Fe, Zn
11 NPLI
CSIR-National Physical Laboratory India
Shankar Gopala
Aggarwal
Prabhat K. Gupta
As, Cd, Fe, Zn
12 NMIJ
National Metrology Institute of Japan Japan
Yanbei Zhu,
Shin-ichi Miyashita As, Cd, Fe, Zn
13
KRISS
Korean Research Institute of Standards &
Science
Korea,
Republic of Yong-Hyeon Yim As, Cd, Fe, Zn
14
SIRIM
National Metrology Laboratory, SIRIM
BERHAD
Malaysia Osman Zakaria As, Cd, Fe, Zn
15 CENAM
Centro Nacional de Metrologia Mexico
Judith Velina Lara
Manzano As, Cd, Fe, Zn
16 HSA
Health Sciences Authority Singapore Richard Shin Fe
17
JSI
Jozef Stefan Institute, Department of
Environmental Sciences
Slovenia Milena Horvat As, Cd, Fe, Zn
18 NIMT Thailand Charun Yafa As, Cd, Fe, Zn
Page 4 of 47
No. Institute Country Contact person
Results
submitted for
measurand
National Institute of Metrology (Thailand)
Remarks: (i) KRISS did not submit results for Fe due to contamination problems found by the institute.
(ii) Both NMIJ and JSI submitted two sets of results using different determination techniques.
3. Samples and Instructions to Participants
3.1. Materials
About 13 kg of dried shrimps was purchased from the local market in Hong Kong. The dried
shrimps were confirmed to contain quantities of incurred iron, zinc, arsenic and cadmium.
The dried shrimps were rinsed with anhydrous methanol to remove dirt and foreign matter
and air-dried in a Class 1000 cleanroom. The air-dried shrimps were blended in a high-speed
blender (25000 revolutions per minute), then de-fatted with n-hexane and air-dried in the
cleanroom. The air-dried sample was further blended and ground to powder using a
high-speed blender (25000 revolutions per minute). The powder was subject to a sieving
process through 200 m calibrated sieves. The sieved powder was thoroughly homogenized
in a 3-dimensional mixer for 5 days. The powdered material was irradiated using a 137
Cs
gamma source at a dose of about 10 kGy for disinfection. The irradiated material was
packed into pre-cleaned and nitrogen-flushed amber glass bottles. About 300 bottles, each
containing about 25 g of powered sample, were prepared. Finally, each bottled sample was
vacuum-sealed in a polypropylene bag and stored at room temperature (20 ± 5 C) prior to
distribution or use.
3.2. Homogeneity and Stability Study
The homogeneity study was conducted after the testing material was bottled and irradiated.
10 bottles of the test material (conditioned at 20 ± 5 C) were randomly selected from the
whole lot of bottles prepared. Two test portions of 0.5 g were taken from each bottle for
analysis.
The test portions were digested using microwave-assisted digestion. Following validated
procedures, the digested samples and method blanks were analysed using standard additions
with high resolution ICP-MS for the analysis of As, Cd and Zn, and using standard additions
with ICP-AES for the analysis of Fe.
ANOVA technique was applied to assess the between-bottle heterogeneity and the standard
uncertainty originated from the between-bottle heterogeneity was calculated using the
equation (1) given below in accordance with ISO Guide 35:2006 [1]. The results are
Page 5 of 47
summarized in Table 2.
within
withinbb
2
MSνn
MSu (1)
where
ubb is the standard uncertainty due to between bottles heterogeneity;
MSwithin is the mean square of within bottles variance;
MSwithin is the degree of freedom of MSwithin;
n is the number of replicates.
Table 2. Summary of homogeneity study results
Measurand ANOVA test on heterogeneity Relative standard uncertainty due to
between-bottle heterogeneity, ubb (%) F-statistics Critical value
As 1.22 3.02 0.95
Cd 2.08 3.02 1.21
Fe 1.25 3.02 1.05
Zn 1.40 3.02 1.26
The homogeneity study results indicated that no significant heterogeneity was observed in
the test material. The test material was considered fit for the purpose of the supplementary
comparison.
Long-term and short-term stability studies were conducted for the test material using the
same analytical procedures as for the homogeneity study. The long-term stability is
associated with the behavior of the test material under storage in participating laboratories
while the short-term stability studies aimed to show the stability of the material during its
transport. The long-term stability was conducted at 20 ºC covering the period from the
distribution of test material to the deadline for submission of results. The short-term stability
was conducted at 40 ºC and 50 ºC over a 4-week period (sampling points: 1 week, 2 weeks
and 4 weeks).
The trend-analysis technique proposed by ISO Guide 35:2006 [1] was applied to assess the
stability of the test material at 20 ºC, 40 ºC and 50 ºC. The basic model for the stability study
is expressed as the equation (2).
Y = 0 + 1X + (2)
Page 6 of 47
where 0 and 1 are the regression coefficients; and denotes the random error component.
With appropriate t-factors, 1 can be tested for significance of deviation from zero. Table 3
summarizes the results of the stability tests at 20 ºC, 40 ºC and 50 ºC respectively.
Table 3. Summary of stability study results
Measurand p-value for significance test for 1
20 ºC 40 ºC 50 ºC
As 0.267 0.583 0.931
Cd 0.173 0.649 0.640
Fe 0.142 0.378 0.570
Zn 0.668 0.569 0.173
As all p-values were greater than 0.05, it was concluded that the corresponding 1 value was
not significantly deviated from zero at 95% level of confidence. In other words, no
instability was observed for the test material at 20 ºC, 40 ºC and 50 ºC during the testing
period. The test material was considered fit for the purpose of the supplementary
comparison.
To monitor the highest temperature that the test material would be exposed to during the
transportation, temperature recording strips were sent along with the test material to the
participating institutes. According to the information provided by the participants in the
Sample Receipt Forms, the maximum temperatures that the test material experienced were
all below 40 ºC.
3.3. Instructions to Participants
Participants were free to choose the analytes and any analytical methods for examination.
They were advised to mix the sample thoroughly before processing. A sample size of at least
0.5 g was recommended for testing. Participants were requested to perform at least three
independent measurements on three separate portions of the sample and to determine the
mass fractions of the analytes of interest. For determination of dry mass correction, a
minimum of three separate portions (recommended size to be about 1 g each) of the sample
was recommended to be placed over anhydrous calcium sulphate (DRIERITE®) in a
desiccator at room temperature for a minimum of 10 days until reaching a constant mass.
Participants were also advised to carry out dry mass correction and analysis of the test
material at the same time.
Participants were asked to report the mean value of at least 3 independent measurements of
the mass fractions of measurands in g/g for arsenic (total), cadmium, iron and zinc on a dry
Page 7 of 47
mass basis and its associated uncertainty (combined standard uncertainty at 1 sigma level).
Participants were requested to provide (i) description of analytical methods (including
sample dissolution procedures if any); (ii) details of the uncertainty estimation (including
complete specification of the measurement equations and description of all uncertainty
sources and their typical values); and (iii) sources and purity of any reference materials used
for calibration purposes.
4. Methods of Measurement
ICP-MS, AAS and INAA were widely used by the participants. The dissolution method
mostly used was microwave assisted digestion. A summary of the methods of measurement
used by the participants is given in Table 4. The information about dry mass correction is
shown in Table 5.
Table 4. Summary of methods of measurement used by the participants
Capabilities/Challenges Not tested Tested Specific challenges
encountered
Sample preparation
Procedures used to prepare samples for irradiation;
determination of the mass basis (e.g., determination of
dry mass basis); procedures to minimize sample loss
during preparation; procedures to minimize
contamination with the elements of interest (highest
difficulty for determination of low levels of elements that
are ubiquitous in the sample preparation environment).
ANSTO, JSI,
KRISS
JSI: Aliquots varied from 0.23 to
0.24 g. Samples were pelletized
using a manual hydraulic press
into pellets 10 mm in diameter
and 2.8 mm high. Each pellet was
sealed in polyethylene foil.
KRISS: Aliquots of about 0.16 g
of the sample were pelletized
using a manual hydraulic press in
diameter 13 mm and 2 mm thick.
Standards preparation
Procedures used to prepare element standards or other
comparators used for standardization. (e.g., low
difficulty for use of pure elements or compounds; higher
difficulty for procedures involving dissolution and
dilution, or dilution with solid matrices.)
All JSI: IRMM-530R Al-0.1%Au
alloy in form of foil with
thickness of 0.1 mm was used.
Discs of about 6 mm in diameter
were prepared. Each disc was
sealed in polyethylene foil.
KRISS: Arsenic standard solution
was transferred to cellulose filter
papers. They were air dried and
pelletized using a manual
hydraulic press in diameter 13
mm and 1.3 mm thick.
General applications
Procedures associated with specific method of NAA and
the evaluation of the associated uncertainties for
comparator NAA, ko NAA, or other method specific
parameters not described below.
ANSTO, JSI,
KRISS
JSI: A sample and standard
Al-0.1%Au were stacked
together, fixed in the polyethylene
vial in sandwich form and
irradiated in the TRIGA reactor.
Characterization of irradiation
channel in the carousel facility
(CF) of TRIGA reactor and
absolute calibration of the HPGe
detector are needed. Optimization
and validation of the k0-INAA
with different matrix certified
reference materials are necessary.
Concentration levels in the
sample for As, Fe and Zn have to
be suitable for INAA.
Determination of peak areas (complex
spectra/small peaks)
Procedures used to determine peak areas. (e.g., high
difficulty for small peak areas on complex backgrounds
or determination of areas for multiple unresolved peaks.)
ANSTO, JSI,
KRISS
JSI: For peak area evaluation, the
HyperLab 2002 program was
used. No difficulties in net peak
areas determination were
encountered for As-76 at 559.1
Page 44 of 47
Capabilities/Challenges Not tested Tested Specific challenges
encountered
keV, Fe-59 at 1099.3 keV and
1291.6 keV, and for Zn-65 at
1115.5 keV. Expected peak of
Cd/In-115m at 336.2 keV was
below the background.
KRISS: Net count rate of the peak
of the primary gamma-ray energy
(559 keV) was small (~ 3 cps) but
not so bad for qualification.
Correction for spectral interferences
Procedures used to determine peak areas from
interfering nuclides and subtraction of the appropriate
number of counts from the peak of interest. Level of
difficulty increases with the number of corrections
needed and the magnitude of the corrections relative to
the total peak area.
All JSI: Negligible background
spectrum corrections were used in
this study (subtraction of recent
background spectrum for all
gamma spectra was applied). No
corrections for gamma-ray
interferences were applied for
radionuclides As-76, Fe-59 and
Zn-65.
KRISS: No gamma-ray peak from
the elements which might cause
spectral interference with 559
keV of As-76 was found.
Correction of fast neutron and fission
interferences
Procedures used to determine the contributions from fast
neutron reactions or fission of U to the peak area of
interest. The level of difficulty is related to the magnitude
of the corrections needed.
All JSI: Used irradiation channel in
the CF of the TRIGA reactor
(IC-40) has a
thermal-to-epithermal flux ratio
of 28.6 and a thermal-to-fast flux
ratio of 7.8. For the studied
radionuclides the threshold
reactions are negligible.
KRISS: The irradiation facility is
well thermalized.
Fission interference does not
cause any problem for As
analysis.
Corrections for sample and standard
geometry differences
Procedures used to determine correction factors for
differences in sample and standard irradiation and
counting geometries. These may include, e.g., use of flux
monitors to determine irradiation geometry correction
factors, and calculated correction factors based on
measured thicknesses and sample-to-detector distances.
Level of difficulty increases with the magnitude of the
correction.
All JSI: A standard Al-0.1%Au was
used as comparator and neutron
flux monitor. A sample and
standard Al-0.1%Au were stacked
together, fixed in the polyethylene
vial in sandwich form and
irradiated. Based on this
procedure, corrections for axial
neutron flux gradient inside the
polyethylene vial were applied.
Differences in sample/standard
geometry are taken into account
and they are calculated by the
Kayzero for Windows
(KayWin®) software.
Corrections or uncertainty assessments for
high count rates
All JSI: HPGe detector with 40 %
relative efficiency connected to
Page 45 of 47
Capabilities/Challenges Not tested Tested Specific challenges
encountered
Procedures used to correct for losses in the analyzer due
to high count rates; e.g., set up and validation of
loss-free counting hardware, use of mathematical
corrections for pulse pileup as a function of analyzer
dead time, etc. Level of difficulty increases with the
magnitude of the correction.
MULTIPORT II multichannel
analyzer (Canberra) and
GENIE-2000 Spectroscopy
software were used.
Measurements were carried out at
such distances that the dead time
was kept below 5 % with
negligible random coincidences.
KRISS: Detector dead time was
less than 4 %.
Corrections for neutron absorption or
scattering differences between samples and
standards
Procedures used to correct for differences between
neutron exposure of samples and standards associated
with differences in the absorbing and scattering power;
e.g., corrections derived from measurements of different
amounts of materials or thicknesses of materials, or
calculations based on cross-section values to correct for
neutron attenuation. Level of difficulty increases with the
magnitude of the correction.
All JSI: The standard Al-0.1%Au
(nuclide Au-198 (T1/2=2.695 d)
at gamma line of 411.8 keV) was
used for axial neutron flux
gradient corrections in the
sample. Radial flux gradient is
negligible due to similar diameter
of sample and standard. Thermal
and epithermal self-shielding
factors are equal to 1.
KRISS: Major composition of the
sample is nearly the same as that
of cellulous filter paper (standard
comparator).
Corrections for differences in neutron
exposure of samples and standards
For some NAA applications, samples and standards are
irradiated individually and corrections are needed for
any differences in neutron exposures. Corrections may
be based on, e.g., results from flux monitors or estimates
based on knowledge of the facility.
All JSI: The samples and standards
were irradiated together.
KRISS: Neutron flux monitors
(Al-Au foil, IRMM-530R) were
used for the correction.
Corrections for gamma-ray attenuation
Procedures used to correct for differences in gamma-ray
attenuation between samples and standards; typically
relevant only for high-z sample or standard matrices and
where samples and standards differ. Level of difficulty
increases with the magnitude of the correction.
All JSI: Corrections for gamma-ray
attenuations in sample/standard
were calculated by Kayzero for
Windows (KayWin®) software
via effective solid angle
calculations (SOLCOI
subroutine). Different measuring
distances from the top of the
HPGe detector for sample and
standard can be used due to
absolute calibration of the HPGe
detector.
KRISS: Major composition of the
sample is nearly the same as that
of cellulous filter paper (standard
comparator).
Page 46 of 47
Inorganic Core Capabilities Table APMP Supplementary Comparison: APMP.QM-S5 Institutes: INTI, NIS, NPLI Method: AAS (FAAS, GF-AAS or electrothermal AAS, HG-AAS) Analytes: INTI : Fe, Zn by FAAS; As, Cd by GF-AAS NPLI: Fe, Zn by FAAS; As by HG-AAS NIS: As, Cd by electrothermal AAS; Fe, Zn by FAAS
Capabilities/Challenges Not tested Tested Specific challenges
encountered
Contamination control and correction
All techniques and procedures employed to reduce potential
contamination of samples as well as blank correction
procedures. The level of difficulty is greatest for analytes that are
environmentally ubiquitous and also present at very low
concentrations in the sample.
INTI, NIS, NPLI INTI (Cd): Low
concentration in the
sample.
Digestion/dissolution of organic matrices
All techniques and procedures used to bring a sample that is
primarily organic in nature into solution suitable for liquid
sample introduction to the ETA-AAS.
INTI, NIS, NPLI NIS: Dissolution should
be carried out carefully
and completely because
incomplete dissolution
may affect the element
conc.
Digestion/dissolution of inorganic matrices
All techniques and procedures used to bring a sample that is
primarily inorganic in nature into solution suitable for liquid
sample introduction to the ETA-AAS.
INTI, NIS
Volatile element containment
All techniques and procedures used to prevent the loss of
potentially volatile analyte elements during sample treatment and
storage.
INTI, NIS INTI: MW with closed
vessel.
NIS: It may be lost during
the dissolution process.
Pre-concentration
Techniques and procedures used to increase the concentration of
the analyte introduced to the ETA-AAS. Includes evaporation,
ion-exchange, extraction, precipitation procedures, but not vapor
generation procedures.
NIS
Matrix separation
Techniques and procedures used to isolate the analyte(s) from
the sample matrix to avoid or reduce interferences caused by the
matrix. Includes ion-exchange, extraction, precipitation
procedures, but not vapor generation procedures.
NIS NIS: Cadmium is affected
by the presence of arsenic
and iron. Std. addition
calibration is used.
Hydride preconcentration/matrix separation of
volatile species.
Coupling of a hydride system to the ETA-AAS and optimization
of conditions.
All
Calibration of analyte concentration
The preparation of calibration standards and the strategy for
instrument calibration. Includes external calibration and
standard additions procedures. Also use of matrix-matched
standards to minimize effect of interferences.
INTI, NIS, NPLI INTI (As): Standard
addition
Signal detection INTI, NIS INTI: Matrix modifier,
Page 47 of 47
The detection and recording of the absorption signals of
analytes. The degree of difficulty increases for analytes present
at low concentrations, of low atomic absorption coefficient.
Requires selection of operating conditions such as light source,