Boric acid-assisted anion-exchange chromatography for separating arsenic species

Abstract

Separation of 11 arsenic species on a single column was achieved by anion-exchange high performance liquid chromatography (HPLC) and selective detection was provided by inductively coupled plasma mass spectrometry (ICPMS). Boric acid was used to selectively modify the retention of arsenosugars. The borate–arsenosugar complexation improved the separation of the following 11 arsenic compounds: tetramethylarsonium ion (TMI), arsenobetaine (AsB), arsenate, arsenite, dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenosugars 1– 4, and an unidentified arsenic compound. The optimised mobile phase composition was 10 mM ammonium phosphate, 30 mM boric acid at pH 8.5. Rice and rice cereal extracts were analyzed using this method revealing the presence of arsenite, arsenate, DMA, and an unidentified arsenic species that has the same retention time as that of arsenosugar 2. Relative standard deviation of retention time from analyses of arsenic in different sample matrices, Fucus serratus, rice, rice cereal, oyster, dogfish, and mushroom extracts, was less than 1.0%, demonstrating the robustness of the separation method.