OFF-LINE SEPARATION AND DETERMINATION OF INORGANIC ARSENIC SPECIES INNATURAL-WATER BY HIGH-RESOLUTION INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY WITH HYDRIDE GENERATION COMBINED WITH REACTION OF ARSENIC(V) AND L-CYSTEINE

A method is presented for the determination of inorganic arsenic speci es by hydride generation high resolution inductively coupled plasma ma ss spectrometry. In the presence of 1.5 mg/ml of L-cysteine, arsenic(V ) is indirectly determined using the difference between As(III) concen trations determined after 2 and 8 min of reaction time, whereas the As (III) concentration is obtained by taking the difference between the c oncentration of arsenic(III) determined after 8 min and the concentrat ion of arsenic(III) converted from arsenic(V) after 8 min. 25 fold amo unts of arsenic(III) and 100 fold amounts of arsenic(V) hardly affecte d the determination of 1 ng/ml arsenic(V) and 100 ng/l arsenic(III), r espectively. Interferences from transition metal ions were removed by using a Chelex 100 resin. The detection limits for arsenic(III) and ar senic(V) were 11.8 and 39.7 ng/l, respectively. The proposed method fo r the simultaneous determination of inorganic arsenic species was appl ied to the determination of As(III) and As(V) in spiked and Japanese s tandard river water samples. Agreement within statistical uncertainty was obtained in all instances. (C) 1998 Published by Elsevier Science B.V.