Determination of arsenic species in fish by directly coupled high-performance liquid chromatography–inductively coupled plasma mass spectrometry

Abstract

Using directly coupled high performance liquid chromatography–inductively coupled plasma mass spectrometry, non-toxic arsenobetaine was identified as the major arsenic species in cod, dab, haddock, mackerel, plaice and whiting. The fish was caught in coastal waters around Plymouth, UK and purchased from local markets. Arsenic levels ranged between 1.0 mg kg^–1 dry mass, in the mackerel, to 187 mg kg^–1 dry mass, in the plaice. Mackerel also contained dimethylarsinic acid (DMAA) and possibly a lipid bound arsenic species. Levels of the toxic inorganic species were low in all cases. No monomethylarsonic acid was recorded in any of the fish. No degradation of arsenobetaine to more toxic species was observed when an enzymic digestion procedure, based on the action of trypsin, was applied to the fish, with the possible exception of one of the plaice samples for which DMAA was characterized in the digest at the mg kg^–1 level. For total arsenic determinations, nitrogen addition ICP-MS was used to overcome the potential interference from ⁴⁰Ar³⁵Cl⁺. The results obtained compared well with certified values for the dogfish reference material DORM-1.