Species-specific isotope dilution-GC-ICP-MS for accurate and precise measurement of methylmercury in water, sediments and biological tissues

Abstract

Species-specific isotope dilution (SSID) in combination with gas chromatography-inductively coupled plasma-mass spectrometry (GC-ICP-MS) has been developed for the separation and determination of methylmercury (MeHg) in water, sediments and biological tissues. Optimum conditions for the measurement of isotope ratios on the transient chromatographic peaks have been established. SSID analysis was performed using a laboratory synthesized enriched spike of Me¹⁹⁸Hg. Isotope ratio precision based on the peak area measurements was 1.4% RSD for 50 pg (as Hg). The absolute detection limits obtained with GC-ICP-MS were 4.3 pg for ¹⁹⁸Hg and 8.1 pg for ²⁰²Hg, respectively. Analytical precision was typically less than 3.6% RSD over eight repeated measurements. The accuracy of the method has been compared with the method with Tl as internal standard and further validated with certified reference materials (ERM-cc580 for sediments and Tort-2 for the biological tissues). The results obtained by SSID-GC-ICP-MS were in good agreement with the certified reference values.