High performance liquid chromatography inductively coupled plasma mass spectrometry for speciation of arsenic compounds in urine

Speciation of urinary arsenic is very important to know the extent of human exposure to inorganic arsenic and also from toxicity point of view. A high performance liquid chromatography inductively coupled plasma mass spectrom etry (HPLC-ICP-MS) system for speciation of arsenite, arsenate, monomethyl arsonic acid (MMAA), dimethyl arsenic acid (DMAA) and arsenobetaine (AB) in a single run in urine samples has been developed. The method is based on a nion exchange high performance liquid chromatography (HPLC) coupled on-line to inductively coupled plasma mass spectrometer (ICP-MS). Detection limits for the five arsenic species in urine samples are between 0.01 and 0.04 mu g l(-1). To validate the method, Standard Reference Material, toxic metals in freeze-dried urine SRM 2670 containing both normal and elevated levels of arsenic have been analyzed for arsenic species. Our results of arsenic s pecies in Standard Reference Material SRM 2670 have been compared with the results of seven other laboratories. The method has been applied to determi ne the arsenic species in urine samples of two groups of people from two ar senic-affected villages of two districts, out of the nine affected district s of West Bengal, India. These two groups were using arsenic-contaminated w ater a few years ago, but are now supposed to be using safe water for drink ing and cooking, as safe sources have been installed. From their urine spec iation, the nature of exposure of individuals to arsenic compound could be predicted. It is concluded that, even though these groups are using safe wa ter, they cannot avoid, from time to time, arsenic contamination as many wa ter sources of the surrounding areas are arsenic contaminated. (C) 2000 Els evier Science B.V. All rights reserved.