Determination of arsenic species in human urine using high performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS)

Abstract

A speciation technique for arsenic (As) has been applied using ion pair reverse phase-high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (RP-HPLC-ICP-MS). Six As-species (arsenite, arsenate, dimethylarsinic acid, dimethylarsinous acid, monomethylarsonic acid and monomethylarsonous acid) have been separated with isocratic elution within less than 6 minutes. A cation exchange column was used for separation of AsB, AsC, Tetra (Me₄As⁺) and TMAsO. The As chemical form and oxidation state is highly important in respect to toxicity; therefore total As-determination is insufficient for a complete toxicological evaluation and risk assessment. Arsenic-speciation has been studied on urine samples of children from an As-affected area in the Iron Quadrangle, Brazil. DMAs^V and MMAs^V were the major urinary metabolites in these samples. The mean value for total As-concentration of all samples (n = 15) was 26.3 ng As mL⁻¹ with a range of 16.1 to 55.2 ng As mL⁻¹. TMAsO and AsC (arsenocholine) were not detected in this study. In most samples, monomethylarsonous acid [MMAs^III] was detected up to 2.0 ng As mL⁻¹. DMAs^III was not detected at any time, most probably due to volatilisation and some oxidation to DMAs^V. The chromatographic recoveries, calculated from ([sum(species) × 100]/total As in urine samples), ranged from 77.4 to 94.9%. This work also contributes to the pertinent discussion regarding the reliability of MMAs^III/DMAs^III speciation in urine.