IAEA Reference Materials
Reference
Sheets
IAEA-086
METHYLMERCURY, TOTAL MERCURY AND OTHER TRACE ELEMENTS IN HUMAN HAIR
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-86 represents hair with a
low 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 The hair was cryogenically homogenized using the stainless steel "CryoPalla"
mill at the KFA-Juelich Specimen Bank facility [2]. The hair was subjected
to consecutive millings, until approximately 70% was below 0.071mm 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 [3].
Date of Release:
November 1997
|
Unit Price:
130 €
|
Unit Size:
5 g
|
| 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-86(.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
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 [4].
Homogeneity
The
material was analyzed for total mercury and methylmercury 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 Hg
and Zn, 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 difference observed within and between the sub-batches
did not exceed 3%, compared to individual measurement uncertainties, which
were 2-7%, relative, for total Hg, and 2-9%, relative, for methylmercury.
Sample sizes of 10 mg each were taken for the homogeneity tests using INAA,
done on the final material. The results for total Hg by INAA showed a relative
deviation of 2.6%, comparable to the measurement uncertainties, 24%, relative.
The results for Zn gave similar results, with no significant differences observed
greater than 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 [3].
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
Stability
tests were performed with the spiked material coded IAEA-85. These 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 IAEA-85 [4].
Since the matrix
of IAEA-86 is identical to that of IAEA-85, it is not expected that the measurands
in the low level material would behave any differently, but would remain similarly
stable.
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 [4].
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-86 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] |
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. |
| [3] |
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 |
| [4] |
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
