Speciation analysis of arsenic and selenium compounds in environmental and biological samples by ion chromatography-inductively coupled plasma dynamic reaction cell mass spectrometer

An inductively coupled plasma mass spectrometer (ICP-MS) was used as an ion chromatographic (IQ detector for the speciation analysis of arsenic and selenium. The arsenic and selenium species studied included arsenite [As(Ill)], arsenate [As(V)], monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), selenite [Se(IV)] and selenate [Se(VI)]. Gradient elution using (NH(4))(2)CO(3) and methanol at pH 9 allowed the chromatographic separation of all species in less than 12 min. Effluents from the IC column were delivered to the nebulization system of ICP-DRC-MS for the determination of arsenic and selenium. The potentially interfering (38)Ar(40)Ar(+) and (40)Ar(40)Ar(+) at the selenium masses m/z 78 and 80 were reduced in intensity by approximately 3 orders of magnitude by using 0.6 mL min(-1) CH(4) as reactive cell gas in the DRC while an Rpq value of 0.3 was used. Meanwhile, arsenic was determined as the adduct ion (75)As(12)CHH(+) at m/z 89, which is more sensitive than (75)As. The limits of detection for arsenic and selenium were in the range of 0.002-0.01 ng mL(-1) and 0.01-0.02ng mL(-1), respectively, based on peak height. The relative standard deviation of the peak areas for five injections of 5 ng mL(-1) As and Se mixture was in the range of 2-4%. The concentrations of arsenic and selenium species have been determined in urine samples collected locally. The major As and Se species in urines were AsB, DMA and probably selenosugar at concentration of 20-40, 15-19 and 17-31 ng mL(-1), respectively. The recoveries were in the range of 94-105% for all the determinations. This method has also been applied to determine various arsenic compounds in two fish samples. In this study, a simple and rapid microwave-assisted extraction method was used for the extraction of arsenic compounds from fish. The arsenic species were quantitatively leached with an 80% v/v methanol solution in a focused microwave field during a period of 5 min. (c) 2007 Published by Elsevier B.V.