Off-line separation and determination of inorganic arsenic species in natural 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 species by hydride generation high resolution inductively coupled plasma mass spectrometry. In the presence of 1.5 mg/ml of L-cysteine, arsenic(V) is indirectly determined using the difference between As(III) concentrations determined after 2 and 8 min of reaction time, whereas the As(III) concentration is obtained by taking the difference between the concentration of arsenic(III) determined after 8 min and the concentration of arsenic(III) converted from arsenic(V) after 8 min. 25 fold amounts of arsenic(III) and 100 fold amounts of arsenic(V) hardly affected the determination of 1 ng/ml arsenic(V) and 100 ng/l arsenic(III), respectively. Interferences from transition metal ions were removed by using a Chelex 100 resin. The detection limits for arsenic(III) and arsenic(V) were 11.8 and 39.7 ng/l, respectively. The proposed method for the simultaneous determination of inorganic arsenic species was applied to the determination of As(III) and As(V) in spiked and Japanese standard river water samples. Agreement within statistical uncertainty was obtained in all instances. (C) 1998 Published by Elsevier Science B.V.