Speciation determination of arsenic in urine by high-performance liquid chromatography–hydride generation atomic absorption spectrometry with on-line ultraviolet photooxidation†

Abstract

A coupled system for arsenic speciation determination based on high-performance liquid chromatography (HPLC), on-line UV photooxidation and continuous-flow hydride generation atomic absorption spectrometry (HGAAS) was built from commercially available modules with minor modifications to the electronic interface, the software and the gas–liquid separator. The best results were obtained with strong anion-exchange columns, Hamilton PRP X-100 and Supelcosil SAX 1, and gradient elution with phosphate buffers containing KH₂PO₄–K₂HPO₄. The on-line UV photooxidation with alkaline peroxodisulfate, 4% m/v K₂S₂O₈–1 mol l^–1 NaOH, in a PTFE knotted reactor for 93 s ensures the transformation of inorganic As^III, monomethylarsonate, dimethylarsinate, arsenobetaine, arsenocholine, trimethylarsine oxide and tetramethylarsonium ion to arsenate. About 32–36 HPLC–UV–HGAAS runs could be performed within 8 h, with limits of detection between 2 and 6 µg l^–1 As, depending on the species. The method was applied to the analysis of spot urine samples and certified urine reference materials (CRMs). Upon storage at 4 °C, reconstituted CRMs are stable for at least 2 weeks with respect to both their total arsenic content and the individual species distribution.