Development of a Common Procedure for the Determination of Methylmercury, Ethylmercury and Inorganic Mercury in Human Whole Blood, Hair and Urine by Triple Spike Species-Specific Isotope Dilution Mass Spectrometry.

Abstract

We report the first common methodology for the simultaneous determination of methylmercury (MeHg), ethylmercury (EtHg) and inorganic mercury (Hg(II)) in human blood hair and urine. With the exception of the initial sample mass (0.15 g for blood, 0.5 g for urine and 0.1 g for hair), the same sample preparation and GC-ICP-MS measurement conditions are employed for the three matrices providing experimental values in agreement with the certified values in the analysis of NIST SRM 955c (Caprine blood) Level 3 and the certified human hairs IAEA 085 and IAEA 086. Also, the method provides quantitative recoveries for the three Hg species in the analysis of fortified human urine samples at 1, 2 and 5 ng Hg g-1. Mercury species concentrations for levels 2 and 4 of SRM 955c are reported here for the first time. A systematic interconversion of EtHg into Hg(II) was obtained for all matrices reaching values up to 95% in blood, 29% in hair and 11% in urine. MeHg dealkylation was also observed in a lesser extent in blood and hair analyses but it was not observed when analyzing urine samples. Hg methylation was not observed in any matrix. The amount of NaBPr4 added for derivatization has been found to be the main responsible of Hg species interconversion. This work demonstrates for the first time, that experimental conditions optimized for SRM 955c (caprine blood) are not valid for human blood samples as the optimum initial sample amount for a real sample is more than three times lower than that for SRM 955c.