Simultaneous determination of oxo- and thio-arsenic species using HPLC-ICP-MS

A method for simultaneous analysis of common oxo-arsenic species and their thio-analogues by coupling ion-pair liquid chromatography to inductively coupled plasma mass spectrometry was developed and validated. The chromatographic separation was performed using a C8 stationary phase and a mobile phase containing 1.2 mmol/L tetramethylammonium hydroxide, 4 mmol/L malonic acid, 6.2 mmol/L sodium butane-1-sulfonate, and 0.05 % (v/v) methanol. Under these conditions, the 11 arsenic species (arsenite, arsenate, dimethylarsinic acid, monomethylarsonic acid, arsenobetaine, arsenocholine, tetramethylarsonium cation, trimethylarsine oxide, dimethyldithioarsinic acid, monomethylmonothioarsinic acid, and trimethyarsine sulfide) were separated. The detection limits for these species ranged from 1.4 to 4.0 ng/g As. The method was applied to the analysis of fish, crustacean, mussel, cephalopod and mushroom samples. Thio-arsenic species DMDTA(v) were found in mussel Mytilus chilensis and cuttlefish Sepis pharaonis samples in very low contents of 23 and 21 ng/g As, respectively. All seafood samples contained predominantly arsenobetaine (330-8570 ng/g As); other As species were present at various contents from 7 to 325 ng/g As.