Ion-exclusion chromatography combined with ICP-MS and hydride generation-ICP-MS for the determination of arsenic species in biological matrices

A sensitive and robust method for the determination;of eight inorganic and organic arsenic species by ion-exclusion liquid chromatography combined wit h inductively coupled plasma mass spectrometry (LC-ICP-MS) and. LC-hydride generation-ICP-MS (LC-HG-ICP-MS) is described. The species are arsenite (As -III), arsenate (As'), monomethylarsonic acid (MMAs), dimethylarsinic acid (DMAs), arsenobetaine (AsB), trimethylarsine oxide (TMAsO), tetramethylarso nium salt (TMAs) and arsenocholine salt (AsC). A good separation of seven a rsenic species, As-III, As-v, MMAs, DMAs, AsB, TMAsO, and AsC or TMAs, was achieved by using an ion-exclusion column packed with a carboxylated methac rylate resin and 0.35 mmol l(-1) of a sodium sulfate solution adjusted to p H 3.8 as the mobile phase. The detection limits of the eight arsenic specie s obtained by LC-ICP-MS ranged from 0.067 to 0.34 ng As ml(-1) using an inj ection volume of 50 mul. A hydride generation technique improved the detect ion limits of As-III, As-v, MMAs, DMAs and TMAsO to 0.016-0.075 ng As ml(-1 ) while AsB, TMAs and AsC were not detectable. The relative standard deviat ions of five replicates of a standard of each arsenic species by the former method ranged from 1.3 to 3.3% and those by the latter method, from 1.8 to 3.1%. The proposed methods were successfully applied to the determination of five arsenic species in human urine and six species in an extract from t una fish tissue. The only necessary pretreatment for these analyses involve d filtration with a 0.45 mum membrane and the ArCl polyatomic interference, due to a large amount of chloride in the biological samples on As-75 measu rement, was eliminated by the described LC separation. In addition, serious deterioration in column performance and a decrease in the sensitivity of I CP-MS were not observed during the experimental period of five months. The LC-ICP-MS and LC-HG-ICP-MS methods were validated by analyzing reference sa mples of human urine and tuna fish tissue.