Determination of inorganic and total mercury in marine biological samples by cold vapor generation inductively coupled plasma mass spectrometry after tetramethylammonium hydroxide digestion

Abstract

A simple, highly-sensitive and accurate method is presented for the determination of both inorganic mercury and total mercury in marine biological samples. 0.1 g of sample was completely solubilized in 1 g of tetramethylammonium hydroxide (TMAH) at room temperature. The TMAH-digested samples were spiked with ¹⁹⁹Hg enriched isotope and diluted to about 14 mL with deionized water. The spiked sample solutions were then analyzed for inorganic mercury determinations by isotope dilution inductively coupled plasma mass spectrometry with cold vapor generation. The solutions were further 5 times diluted with deionized water for total mercury determinations. SnCl₂ reducing agent was used for the inorganic mercury determinations, and NaBH₄ for the total mercury determinations. No reagents other than the reducing agents with acid solutions were used for the mercury determinations. The proposed method was validated by the analysis of three certified reference materials, DORM-2 (dogfish muscle), NIST SRM1566b (oyster) and KRISS tuna CRM. The detection limit of the method was found to be 0.018 ng g⁻¹.