IAEA Reference Materials
Reference
Sheets
IAEA-407
TRACE ELEMENTS AND METHYLMERCURY
IN
FISH TISSUE
Intended
Use
This
material is intended to be used as a reference material for the measurement
of trace elements and methylmercury (MeHg) in fish tissue samples. It can
also be used as a quality control material for the assessment of analytical
procedures, in the elaboration and validation of analytical methods, and for
educational purposes.
Origin
and preparation of the material
A large
quantity of whole fish was collected in 1999 from the North Sea for use as
an intercomparison material. Most of what was collected was herring, but the
sample material also contained capelan and anchovy. It was deep-frozen, freeze-dried,
triple-extracted with acetone to remove fat, and then ground and sieved. The
particle size fraction <250 µm was homogenized by mixing in a rotating
glass bottle for 15 days. After checking for the homogeneity of the sample
material (see below), aliquots of about 35 g were packed into cleaned brown
borosilicate glass bottles with Teflon lined screw caps and sealed in plastic
bags. Approximately 500 bottles were produced.
Date of Release:
September 2003
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Unit Price:
90 €
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Unit Size:
25 g
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| Producer:
Marine Environment Laboratory (MEL) International Atomic Energy Agency B.P. No 800 MC-98012 Monaco |
Supplier:
Analytical Quality Control Services Agency's Laboratories, Seibersdorf A-2444 Seibersdorf, Austria |
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Reference Sheet:  IAEA-407(.pdf) |
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| * | Number
of accepted laboratory results which were used to calculate the recommended
or information values and their respective confidence intervals about
the mean value. |
| (R/I) | Classification assigned to the property value for Analyte (Recommended/Information) |
| # | As inorganic Hg |
The values listed
above were established on the basis of results submitted by laboratories which
had participated in an international intercomparison exercise organized in
2000. The details concerning the criteria for qualification as recommended
or information value can be found in the report (IAEA/AL/144; IAEA/MEL/72),
“Report on the world-wide intercomparison exercise for the determination
of trace elements and methylmercury in fish homogenate IAEA-407” [1].
This report is available free of charge upon request.
Homogeneity
Extensive
homogeneity tests were carried out on this material in order to ensure its
suitability as an intercomparison sample. A homogeneity pre-test was conducted
before bottling the sample material. The between-bottle homogeneity was tested
by the determination of the concentration of some typical elements (Cd, Cr,
Cu, Fe, Mn, Zn) on sample intakes of 0.2 g taken from 10 bottles which were
taken directly from the bulk material, specifically for the purpose of this
pre-test. The within-bottle homogeneity was assessed by 10 replicate determinations
on the re-homogenized content of one bottle. The uncertainty of the analytical
methods was assessed for each element by 5 replicate measurements on one digest
solution.
Both the within-bottle and between-bottle
CV's observed for Cr and Fe were significantly higher than the method CV's
for these elements -- a clear indication that the sample material was not
entirely homogeneous, at least with respect to certain constituents. An F-test
at a significance level of 0.05 was performed for the different metals and
did not reveal significant differences between the within- and between-bottle
variances, indicating that the heterogeneity observed was relatively consistent,
and independent of how the material was distributed.
In spite of the relatively large variations
observed for Cr and Fe, the sample material was bottled and a final homogeneity
test performed on 20 random bottles for Cd and Cu only. The variances observed
for these elements compared well with the variances found in the pre-test.
It was concluded that while not entirely homogeneous for all elements of interest,
the material was homogeneous for most elements and sufficiently so for the
others at an analytical portion of 200 mg and above; it is therefore suitable
for use as an intercomparison sample [1].
Stability
of the material
The
stability of several trace metals was tested to determine the suitability
of this material as a candidate CRM. Five bottles of the IAEA-407 material
were stored in the dark at +20 °C, –20 °C and +60 °C, respectively,
over a period of 18 months (starting in September 2000) and the measurement
of total Hg, Cu, Fe, Mn and Zn was performed at regular intervals during the
storage period. On the basis of these results, it was concluded that no instability
of the material could be demonstrated [1].
Dry weight determination
The
average moisture content of the lyophilized sample after bottling, determined
by drying to a constant weight at 105°C, was found to be 6 %. Since the
moisture content can vary with the ambient humidity and temperature, it is
recommended that the water content of this material be determined in a separate
subsample (not used for analysis) by drying to a constant weight (~24 hours)
at 105°C just prior to analysis. Final results should always be reported
on a dry weight basis.
Instructions
for use
The
recommended minimum sample size for analysis is 200 mg. Analysts are reminded
to take appropriate precautions in order to avoid contaminating the remaining
material in the bottle. The bottle should be thoroughly mixed by shaking before
use and tightly resealed immediately after use. The material should be stored
in the dark and kept below 25 ºC.
References:
| [1] |
Last updated 30 March 2004
