An international group of researchers have developed a new human hair reference material for mercury speciation analysis.
Mercury is a global pollutant and classified by the World Health Organization as a major public health concern. Some inorganic mercury released to the environment is converted mainly by microorganisms into more toxic organic mercury. Organic mercury (methylmercury) is bioaccumulated in organisms and biomagnified in the food web. Humans are mainly exposed to methylmercury via consumption of seafood. Human biomonitoring is requested in order to evaluate actual exposure to the toxin. Hair is the preferred sample type for biomonitoring since it retains mercury well and its testing is non-invasive. The new CRM:
The main mercury species retained in the hair matrix is methylmercury. Certified reference materials (CRMs) for assessing mercury levels are required, as an increasing number of surveys are conducted to evaluate the effectiveness of regulations and policies driven by the Minamata Convention.
Considering the demands of human biomonitoring of hair for mercury and other elements, the researchers developed a material with extended certification to cover some elements with toxicological and nutritional significance. To assure that the material is representative of human hair, contamination sources were minimized with great attention.
About 10 kg of scalp hair was collected from Vietnamese males in a
barbershop in Hanoi. The hair was washed five times in a 0.3% neutral
detergent, rinsed with tap water and finally with distilled water before
drying at 60° overnight. The dried hair was pulverized by the combined
action of a roll crusher, pin mill and air-jet mill to particles with a
size below 74 µm. After rigorous blending, three gram aliquots of the
homogenized hair powder were poured into borosilicate bottles and
sterilized by gamma-irradiation.
An aliquot of 20 mg of the hair powder was sufficient to reach a standard deviation of less than 2.6 % for all certified elements.
The material was stable for the test period (12 months).
10 Laboratories provided results for methylmercury. Techniques used by the laboratories were GC-ECD (8 laboratories) and GC-AFS as well as HPLC-chemiluminescence. There was no bias between the techniques.
Data for total mercury was provided by 19 laboratories. Techniques used were thermal decomposition-AAS (TD-AAS, 12 times), CV-AAS (4 times), CV-AFS (1 times) and ICP-QMS (3 times). The results obtained by ICP-MS were slightly higher than all others and were considered to be outliers and were excluded from the certification.
Results for the other elements were provided by 12 laboratories using ICP-QMS for determination. Unfortunately, the low number of acceptable results for arsenic did not allow for certification.
The following table compares the certified values for NIMD-1 with those of other Human hair CRMs.
| Element || NIMD-01 || NIES-13 || IAEA 086 |
| MeHg as Hg || 0.634 ± 0.071 || 3.8 ± 0.4 || 0.258 ± 0.021 |
| total Hg || 0.794 ± 0.050 || 4.42 ± 0.2 || 0.573 ± 0.039 |
| Cu || 12.8 ± 1.4 || 15.3 ± 1.3|| 17.6 ± 0.9 |
| Zn || 234 ± 29 || 172 ± 11 || 167 ± 7 |
| Se || 1.52 ± 0.29 || 1.79 ± 0.17|| 1.00 ± 0.20 |
| As (info)|| 0.17 ± 0.03 || 0.10 || -|
* all values in mg/kg dry weight
The original study:
Koichi Haraguchi, Mineshi Sakamoto, Akito Matsuyama, Megumi Yamamoto, Dang T. Hung, Hiromitsu Nagasaka, Keisuke Uchida, Yasunori Ito, Hitoshi Kodamantani, Milena Horvat, Hing M. Chan, Matthew Rand, Ciprian M. Cirtiu, Byoung-Gwon Kim, Flemming Nielsen, Akane Yamakawa, Nikolay Mashyanov, Nikolai Panichev, Elena Panova, Tomoaki Watanabe, Naoki Kaneko, Jun Yoshinaga, Ranny F. Herwati, Alfrida E. Suoth, Hirokatsu Akagi, Development of Human Hair Reference Material Supporting the Biomonitoring of Methylmercury,
Anal. Sci., 36/5 (2020) 561-567. DOI: 10.2116/analsci.19SBP07
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