A sensitive analytical technique for arsenic compounds based on single drop microextraction (SDME) coupled in-line with capillary electrophoresis (CE) was developed. The analytes were inorganic As(III) and As(V) as well as organic dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA). In SDME, a drop of an acceptor phase covered with an organic layer is hung at the inlet tip of a separation capillary. By pH adjustment, analytes in the neutral form in an aqueous donor phase are first extracted into the organic layer, and then back-extracted into the acceptor phase. However, the hydrophilic nature of the arsenic compounds, hampering the first extraction into the organic layer, lowers or even eradicates the efficiency of SDME. This problem can be solved by employing the scheme of carrier-mediated counter transport using CH3(C8H17)3N+Cl� (Aliquat 336) as a carrier in the organic layer. Aliquat 336 enhances the transport of the arsenic compounds across the organic layer by forming hydrophobic complexes. The arsenic enrichment is driven by the concentration gradient of hydroxide ion in counter with the arsenic extraction from the donor phase of low pH to the acceptor phase of high pH. After extraction, a portion of the enriched acceptor drop is injected and the arsenic compounds are separated by CE. Thus the whole procedures of SDEM and CE can be performed in a in-line mode using a commercial CE instrument. After optimizing the SDME condition, the enrichment factors obtained for a sample in 1 mM NaCl with 15 min extraction were 37(�1), 65(�10), 320(�13), and 650(�140) for DMA, As(III), MMA, and As(V), respectively. The limits of detection (S/N = 3) with absorbance detection at 200 nm were 3.0, 0.54, 0.24, and 0.20 �M of DMA, As(III), MMA, and As(V), respectively.

Sensitive arsenic analysis by carrier-mediated single drop microextraction coupled with capillary electrophoresis

243rd National Meeting (2012)

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