Speciation of six arsenic compounds using capillary electrophoresis inductively coupled plasma mass spectrometry

Capillary electrophoresis (CE) was used to separate four anionic {arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid and dimethylarsinic aci d } and two cationic forms (arsenobetaine and arsenocholine) of As in a sin gle run. At sufficiently high concentrations, the determination of these co mpounds could be accomplished by means of UV detection. The determination o f low concentrations (<10 mu g l(-1)) of these compounds of interest was ac complished by coupling CE on-line with inductively coupled plasma mass spec trometry (ICP-MS). To accomplish this coupling, a microconcentric nebulizer was used. The modifications necessary to make a conventional CE system com patible with ICP-MS, the optimization of the operation parameters and of sa mple stacking conditions together with the effect of the sheath liquid and of an induced laminar flow are discussed. The analytical figures of merit o f the method were assessed and the limit of determination (based on the pea k height of a peak for which the signal-to-noise ratio is 10:1) was found t o be 1-2 mu g l(-1) As for each species. The recovery for the compounds of interest was determined using a spiked mineral water sample. Samples of min eral water, soil leachate and urine were analyzed with the CE-ICP-MS combin ation.