Arsenic speciation in urine and blood reference materials

Acute and chronic exposure to arsenic is a growing problem in the industrialized world. Arsenic is a potent carcinogen and toxin in humans. In the body, arsenic is metabolized to produce several species, including inorganic forms, such as trivalent (As-III) and pentavalent (As-V), and the methylated metabolites such as monomethylarsonic acid, (MMA(V)), and dimethylarsinic acid (DMA(V)), in addition to arsenobetaine (AsB) which is ingested and excreted from the body in the same form. Each of these species has been reported to possess a specific but different degree of toxicity. Thus, not only is the measurement of total As required, but also quantification of the individual metabolites is necessary to evaluate the toxicity and risk assessment of this element. There are a large number of reference materials that are used to validate methodology for the analysis of As in blood and urine, but they are limited to total As concentrations. In this study, the speciation of five arsenic metabolites is reported in blood and urine from commercial available control materials certified for total arsenic levels. The separation was performed with an anion exchange column using inductively coupled plasma mass spectrometry as a detector. Baseline separation was achieved for As-III, As-V, MMA(V), DMA(V), and AsB, allowing us to quantify all five species. Excellent agreement between the total arsenic levels and the sum of the speciated As levels was obtained.