Six arsenic species, arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine, were separated by coupled column ion chromatography using carbonate and nitric acid as eluents, and were detected by inductively coupled plasma mass spectrometry. Coupling of an anion column with a cation column made the simultaneous determination of both the cationic and the anionic arsenic species possible by ion chromatography. Extremely low detection limits, below 0.2 μg/l (as arsenic), were obtained for all the species studied.