Rapid methods to detect organic mercury and total selenium in biological samples

Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, Michigan 48109, USA. .
Chemistry Central Journal (Impact Factor: 2.19). 01/2011; 5(1):3. DOI: 10.1186/1752-153X-5-3
Source: PubMed


Organic mercury (Hg) is a global pollutant of concern and selenium is believed to afford protection against mercury risk though few approaches exist to rapidly assess both chemicals in biological samples. Here, micro-scale and rapid methods to detect organic mercury (< 1.5 ml total sample volume, < 1.5 hour) and total selenium (Se; < 3.0 ml total volume, < 3 hour) from a range of biological samples (10-50 mg) are described.
For organic Hg, samples are digested using Tris-HCl buffer (with sequential additions of protease, NaOH, cysteine, CuSO4, acidic NaBr) followed by extraction with toluene and Na2S2O3. The final product is analyzed via commercially available direct/total mercury analyzers. For Se, a fluorometric assay has been developed for microplate readers that involves digestion (HNO3-HClO4 and HCl), conjugation (2,3-diaminonaphthalene), and cyclohexane extraction. Recovery of organic Hg (86-107%) and Se (85-121%) were determined through use of Standard Reference Materials and lemon shark kidney tissues.
The approaches outlined provide an easy, rapid, reproducible, and cost-effective platform for monitoring organic Hg and total Se in biological samples. Owing to the importance of organic Hg and Se in the pathophysiology of Hg, integration of such methods into established research monitoring efforts (that largely focus on screening total Hg only) will help increase understanding of Hg's true risks.

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    • "However, we were able to analyze MeHg concentrations in other hair samples collected in Ghana (n ¼7) and Indonesia (n ¼3) from the same mining populations . Methylmercury in representative hair samples was extracted and analyzed following previously published methods (Nam and Basu, 2011). Briefly, hair samples were digested using Tris–HCl, protease, NaOH, cysteine, CuSO 4 , and acidic NaBr. "
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    ABSTRACT: Total mercury (Hg) concentrations in hair and urine are often used as biomarkers of exposure to fish-derived methylmercury (MeHg) and gaseous elemental Hg, respectively. We used Hg stable isotopes to assess the validity of these biomarkers among small-scale gold mining populations in Ghana and Indonesia. Urine from Ghanaian miners displayed similar Δ199Hg values to Hg derived from ore deposits (mean urine Δ199Hg=0.01‰, n=6). This suggests that urine total Hg concentrations accurately reflect exposure to inorganic Hg among this population. Hair samples from Ghanaian miners displayed low positive Δ199Hg values (0.23–0.55‰, n=6) and low percentages of total Hg as MeHg (7.6–29%, n=7). These data suggest that the majority of the Hg in these miners' hair samples is exogenously adsorbed inorganic Hg and not fish-derived MeHg. Hair samples from Indonesian gold miners who eat fish daily displayed a wider range of positive Δ199Hg values (0.21–1.32‰, n=5) and percentages of total Hg as MeHg (32–72%, n=4). This suggests that total Hg in the hair samples from Indonesian gold miners is likely a mixture of ingested fish MeHg and exogenously adsorbed inorganic Hg. Based on data from both populations, we suggest that total Hg concentrations in hair samples from small-scale gold miners likely overestimate exposure to MeHg from fish consumption.
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    • "For hair, a 2 cm segment cut from the proximal end was washed with acetone, rinsed thrice with Milli-Q water, dried overnight and $ 2–5 mg was placed into a nickel sampling boat. Seafood samples ( 41 g) were dried and analyzed as we have previously described (Nam and Basu, 2011). Quality control measures included daily instrument calibration, procedural blanks, replicates, and several certified reference materials including CRM #13 for hair (National Institute for Environmental Studies, Japan), DOLT-4 (dogfish liver; National Research Council, Canada), and QMEQAS for blood and urine (Institut National de Santé Publique du Québec). "
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    ABSTRACT: Background: Mercury is a global contaminant of concern though little is known about exposures in México. Objectives: To characterize mercury levels in pregnant women, children, and commonly consumed seafood samples. Methods: Use resources of the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) birth cohorts to measure total mercury levels in archived samples from 348 pregnant women (blood from three trimesters and cord blood), 825 offspring (blood, hair, and urine) and their mothers (hair), and 91 seafood and canned tuna samples from Mexico City. Results: Maternal blood mercury levels correlated across three trimesters and averaged 3.4. μg/L. Cord blood mercury averaged 4.7. μg/L and correlated with maternal blood from trimester 3 (but not trimesters 1 and 2). In children, blood, hair and urine mercury levels correlated and averaged 1.8. μg/L, 0.6. μg/g, and 0.9. μg/L, respectively. Hair mercury was 0.5. μg/g in mothers and correlated with child[U+05F3]s hair. Mean consumption of canned tuna, fresh fish, canned sardine, and shellfish was 3.1, 2.2, 0.5, and 1.0 times per month respectively in pregnant women. Mean mercury content in 7 of 23 seafood species and 5 of 9 canned tuna brands purchased exceeded the U.S. EPA guidance value of 0.3 μg/g. Conclusions: Mercury exposures in pregnant women and children from Mexico City, via biomarker studies, are generally 3-5 times greater than values reported in population surveys from the U.S., Canada, and elsewhere. In particular, mercury levels in 29-39% of the maternal participants exceeded the biomonitoring guideline associated with the U.S. EPA reference dose for mercury.
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    • "Mercury is considered one of the most toxic elements in almost all forms even in low concentrations as a result of bioavailability, mobility and high bioaccumulation factor (biomagnification factor up to 106 in the food chain) [1-3]. For this reason its determination and speciation is of great interest in all environmental compartments, such as soil, airborne particulate matter and dust, sediment, water, waste, air and biological samples [4-10]. "
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    ABSTRACT: The paper presents the evaluation of soil contamination with total, water-available, mobile, semi-mobile and non-mobile Hg fractions in the surroundings of a former chlor-alkali plant in connection with several chemical soil characteristics. Principal Component Analysis and Cluster Analysis were used to evaluate the chemical composition variability of soil and factors influencing the fate of Hg in such areas. The sequential extraction EPA 3200-Method and the determination technique based on capacitively coupled microplasma optical emission spectrometry were checked. A case study was conducted in the Turda town, Romania. The results revealed a high contamination with Hg in the area of the former chlor-alkali plant and waste landfills, where soils were categorized as hazardous waste. The weight of the Hg fractions decreased in the order semi-mobile > non-mobile > mobile > water leachable. Principal Component Analysis revealed 7 factors describing chemical composition variability of soil, of which 3 attributed to Hg species. Total Hg, semi-mobile, non-mobile and mobile fractions were observed to have a strong influence, while the water leachable fraction a weak influence. The two-dimensional plot of PCs highlighted 3 groups of sites according to the Hg contamination factor. The statistical approach has shown that the Hg fate in soil is dependent on pH, content of organic matter, Ca, Fe, Mn, Cu and SO42- rather than natural components, such as aluminosilicates. Cluster analysis of soil characteristics revealed 3 clusters, one of which including Hg species. Soil contamination with Cu as sulfate and Zn as nitrate was also observed. The approach based on speciation and statistical interpretation of data developed in this study could be useful in the investigation of other chlor-alkali contaminated areas. According to the Bland and Altman test the 3-step sequential extraction scheme is suitable for Hg speciation in soil, while the used determination method of Hg is appropriate.
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