Arsenic is an element widely distributed in the crust of the earth, causing a worldwide problem of groundwater contamination. Four arsenic compounds arsenite [As(III)], dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and arsenate [As(V)] in an unbuffered water sample were enriched by carrier-mediated electromembrane extraction (EME) and then analyzed by off-line coupled capillary electrophoresis. Under an electrical potential, anionic arsenic analytes such as DMA, MMA, and As(V) were transferred from the sample solution to an aqueous acceptor phase, mediated by a carrier CH3(C8H17)3N+Cl� (Aliquat 336) in the supported liquid membrane (SLM). Neutral As(III) was oxidized to As(V) by potassium permanganate and then enriched by EME for indirect determination. Several EME parameters such as the composition of SLM, pH of donor and acceptor phases, extraction temperature, stirring rate, applied voltage, and extraction time were optimized. Under the optimal conditions, the enrichment factors (EFs) of 2300-4200 were obtained for samples of the 4 arsenic species prepared in deionized water. Tap water samples were diluted 10-fold with deionized water and then enriched with EME. Due to the dilution, the overall EFs were 110-290. The limits of detections obtained with a tap water sample using UV absorbance detection at 200 nm were 12 ppb for DMA, 3 ppb for MMA, 6 ppb for As(V), and 6 ppb for As(III), most of which were below the WHO drinking water guideline of 10 ppb total arsenic.

Carrier-mediated electromembrane extraction combined with capillary electrophoresis for sensitive arsenic speciation

248th National Meeting (2014)

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