Simultaneous determination of arsenic and selenium species in phosphoric acid extracts of sediment samples by HPLC-ICP-MS Original Research Article

A new method for the multielemental determination of arsenic and selenium species in sediment extracts is detailed. Anion exchange separation of As(III), As(V), DMA, MMA, Se(IV) and Se(VI) coupled to ICP-MS detection was accomplished in 10 min on a Hamilton PRP-X100 column with step gradient of a NH4H2PO4 based mobile phase (pH = 6). The extraction procedure used 1 g of dry sediment and 12.5 mL of phosphoric acid. One hour of extraction time (end-over-end shaking) and an acid concentration of 0.3 M were regarded as optimum. The estimated detection limits in the sediment ranged between 2 and 40 ng g−1 for the species analysed. Precision, determined at two levels of concentration showed values of coefficient of variation below 20% for the low level (near the LOD) and below 10% for the high level (10 times the low level). Accuracy of the method was assessed through calculation of the recovery of the spiked sediment. Recoveries ranged between 80 and 120% for all the species analysed with the exception of As(III). This low recovery was thoroughly studied and explained through a conversion process of As(III) into As(V) by an air-oxygen oxidation mechanism during the drying step. The method was regarded as suitable for the proper assessment of the potential toxicity of the sediment.