IAEA Reference Materials
Reference
Sheets
IAEA-85
METHYLMERCURY, TOTAL MERCURY AND OTHER TRACE ELEMENTS IN HUMAN HAIR
(METHYLMERCURY SPIKED)
Intended
Use
This material
is intended as reference material primarily for the measurements of total
mercury (Hg) and methylmercury (MeHg), but also for selected trace elements.
The material can also be used for the assessment and control of a laboratory's
analytical work, and for the validation of analytical methods used in a laboratory,
i.e., in general quality assurance within a laboratory and for training purposes.
Origin
and preparation of the material
The material
has been prepared from human hair. IAEA-85 represents hair with an elevated
level of methylmercury.
Ten kg of human
hair were collected and donated to the Agency for preparation of two reference
materials. The material had been previously cut into uniform (1 cm) lengths,
and cleaned with acetone and deionized water following the procedure developed
by IAEA [1]. The material was then split into two portions, each approximately
5 kg, for the two reference materials, and was radiation sterilized at 50
kGy. Afterwards the material was labeled with methylmercury using an established
procedure [2] to achieve an elevated level of methylmercury. During this process
leaching of some trace elements might be possible. The hair was cryogenically
homogenized using the stainless steel "CryoPalla" mill at the KFA-Juelich
Specimen Bank facility [3]. The hair was subjected to consecutive millings,
until approximately 70% was below 0.071 mm grain size. The material was then
bottled, providing 750 5-g units. Sterilization of the material in the bottles
was done at 12kGy using a 60Co Source. Further details can be found
in reference [4].
Date of Release:
November 1997
|
Unit Price:
130 €
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Unit Size:
5 g
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| Producer:
Section of Nutritional and Health-Related Environmental Studies International Atomic Energy Agency P.O. Box 100, A-1400 Vienna Austria |
Supplier:
Analytical Quality Control Services Agency's Laboratories, Seibersdorf A-2444 Seibersdorf, Austria |
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Reference Sheet:  IAEA-85(.pdf) |
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| * |
Number of accepted laboratory results which were used to calculate the
recommended 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 reference values were established
on the basis of results submitted by 74 participants from 68 institutes who
participated in an international intercomparison exercise organized during
1994/1995. The details concerning the criteria for certification of recommended
and information values may be found in the report (IAEA/AL/67) "Intercomparison
Run IAEA-85/IAEA-86; Determination of Methylmercury, Total Mercury and Trace
Elements in Human Hair". This report is in preparation and will be available
upon request free of charge. A shorter version of it has been submitted for
publication in an international journal [5].
Homogeneity
The material
was analyzed to determine the degree of homogeneity. Aliquots from both the
sub-batch of bulk homogenate and from the material after bottling and radiation
sterilization were analyzed for these tests.
Several techniques
were employed: instrumental neutron activation analysis (INAA) for total mercury
and zinc, X-ray fluorescence for total Hg, cold vapor atomic absorption spectrometry
(CV-AAS) for total Hg and gas chromatography with atomic fluorescence spectrometry
detection (GC-AFS) for methylmercury. For the methods employing digestions,
50-100 mg sample sizes were used. The material did not have observable inhomogeneities
greater than the measurement uncertainties (1-3% for CV-AAS, and 2-5% for
GC-AFS). Sample sizes of 10 mg each were taken for the homogeneity tests using
INAA. The observed relative standard deviation of the means within and between
the sub-batches (14%) were on the same order or less than the measurement
uncertainties (about 3.5-3.7%). The measurements for Zn gave similar results,
with no significant differences observed greater than the measurement uncertainties.
The homogeneity
results for total mercury by INAA and XRF on the material after final preparation
were within 2% of the mean value, again comparable to measurement uncertainties.
Thus, the material is considered homogeneous for Hg and Zn at the 10 mg sample
size, and this can be considered comparable homogeneity for the other major
biological trace elements. Further details can be found in reference [4].
Dry
weight determination
The recommended
and information values are expressed on a dry weight basis. For this purpose,
the volatile water content, at the time of analysis, should be determined
in separate sub-samples. The recommended procedure is oven drying at 80°C
for 2 hours or freeze-drying for 48 hours. These procedures have been shown
to yield similar and stable results, which are in agreement with those obtained
by microwave thermogravimetry analysis (within 0.5%).
Stability
of the material
Because the
IAEA-85 material was a spiked, rather than a natural material, there was concern
over possible loss of the spiked MeHg over time. Stability studies have been
evaluated after two years of ambient storage and compared with material stored
at liquid nitrogen temperatures, which have shown no discernible changes in
the mercury, methylmercury or trace element concentrations in this material
[5].
Establishing
of reference values
The recommended
and information values represent overall mean values (excluding data that
were detected and rejected as outliers) calculated on the basis of at least
ten laboratory means. For the total mercury and methylmercury values, the
results submitted by invited expert laboratories were used in addition to
those from the intercomparison means. A confidence interval is given with
each recommended value, which was calculated from the mean of the laboratories'
means. The confidence interval for the information values was calculated in
the same way, but these intervals should be interpreted with caution, because
they did not fulfill all criteria to qualify as recommended values [5].
Instructions
for use
The recommended
minimum sample size is 50 mg for organic (MeHg) analyses and 10 mg for inorganic
analyses. It is recommended to store the material in a dark place, below 20°C
(refrigeration is advised). From experience with similar materials, IAEA-85
is expected to remain stable for at least 5 years under these storage conditions.
References:
| [1] | Cortes-Toro,
E., et al., The significance of hair material analysis as a mean for
assessing internal body burdens of environmental pollutants: Results
from an IAEA co-ordinated research programme, J. Radioanal. Nucl. Chem.
167 (1993) 413-421. |
| [2] | Kratzer,
K., Benes, P., Spevackova, V., "The study of chemical forms of mercury
in human hair and other bio-environmental samples", Report on the Second
Research Co-ordination Meeting for the Co-ordinated Research Programme
on Assessment of Environmental Exposure to Mercury in Selected Human
Populations as Studied by Nuclear and other Techniques, NAHRES-13, IAEA,
Vienna, Austria (1992) 25-31. |
| [3] | Schladot,
J. D., Backhaus, F. W., "Preparation of sample materials for environmental
specimen banking purposes - Milling and homogenization at cryogenic
temperatures", Progress in Environmental Specimen Banking NBS Spec.
Publ. 740, (Wise, S. A., Zeisler, R., Goldstein, G. M., Eds.) U.S. Dept.
Commerce, Washington, D.C. (1988) 184-193. |
| [4] | Stone,
S. F., et al., Production of hair intercomparison materials for the
use in population monitoring programmes for mercury and methylmercury
exposure, Fresenius J. Anal. Chem. 352 (1995) 184-187 |
| [5] | Heller-Zeisler,
S. F., Parr, R. M., Zeisler, R., Certification of two human hair reference
materials issued by the International Atomic Energy Agency, Fresenius
J. Anal. Chem. 360 (1998) 419-422. |
Last updated 9 October 2003
