Mercury speciation analysis in human hair by species-specific isotope-dilution using GC–ICP–MS
Résumé
The authors optimized a mercury (Hg) speciation extn. method for human hair in combination with species-specific isotope-diln. anal. by gas chromatog.-inductively coupled plasma-mass spectrometry (GC-ICP-MS). The method was validated on human hair ref. material RM (IAEA-086), which is recommended for anal. of monomethylmercury (MMHg) and inorg. mercury (IHg). Three reagents, hydrochloric acid (HCl), nitric acid (HNO3), and tetramethylammonium hydroxide (TMAH), and three extn. procedures, at ambient temp. for 12 h, microwave-assisted at 75° for 6 min, and oven heated at 80° for 2 h were tested. Extn. efficiency, recovery, and potential species transformations were evaluated for each method. The most efficient procedures, with recovery of ∼90% for each species with limited demethylation (<5 %) and methylation (0 %), were HNO3 digestion, irresp. of temp., and microwave-assisted TMAH extn. Acidic extn. with HCl induces significant demethylation, with prodn. of artifacts. To correct for potential demethylation artifacts the authors recommend spiking with isotopically enriched stds. before the extn. step.