Determination of inorganic and methylmercury in fish by cold vapor atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry

Simple and rapid analytical procedures for the determination of Hg2+ and methylmercury in fish were proposed after careful optimization of chemical and instrumental parameters for Hg measurement by cold vapor (CV)/hydride generation (HG) atomic absorption spectrometry (AAS) and CV/HG inductively coupled plasma atomic emission spectrometry (ICP-AES). Quantitative extraction of Hg species avoiding any inter-species conversion was achieved by fast microwave assisted solubilization of fish tissue with relatively low amount of tetramethylammonium hydroxide (TMAH) or 6 mol L− 1 HCl. After careful optimization of chemical parameters selective determination of Hg2+ in the presence of excess of methylmercury is attained by using continuous flow CV AAS, 1% m/V SnCl2 as reductant and 0.1 mol L− 1 HCl as reaction medium. Simple calibration curve prepared with aqueous standard of Hg2+ is recommended for its quantification. Both Hg2+ and methylmercury could be determined simultaneously with equal sensitivity by CV/HG ICP-AES directly in the diluted TMAH solution obtained after extraction with 1% m/V NaBH4 as reductant. Quantification of the sum of Hg2+ and methylmercury against calibration curve prepared with aqueous standard of methylmercury is suggested. It should be mentioned that batch hydride generation system with quartz tube heated in air/acetylene flame could also be used for simultaneous determination of both Hg species in fish extracts, with standard additions calibration. The validity of the developed analytical procedures for selective determination of Hg2+ and methylmercury (by difference between the total Hg and Hg2+) is confirmed by the analyses of certified reference material DOLT-1 and reference material IMEP-20. Very close agreement between certified values and analytical results was found.