Electro membrane isolation of nerve agent degradation products across a supported liquid membrane followed by capillary electrophoresis with contactless conductivity detection

Abstract

In the present study, electro membrane isolation (EMI) of four nerve agent degradation products has been successfully explored. In the procedure, a polypropylene sheet membrane folded into an envelope with an open end with its wall pores impregnated with 1-octanol was employed as the artificial supported liquid membrane (SLM). The envelope containing the extractant or aqueous acceptor phase (at pH 6.8) was immersed in the sample or donor phase (also aqueous at a pH of 6.8) for extraction. This ensured that the target analytes were fully ionized. A voltage was then applied, with the negative electrode placed in the donor phase with agitation, and the positive electrode in the acceptor phase. The ionized analytes were thus driven to migrate from the donor phase across the SLM to the acceptor phase. The factors influential to extraction: type of organic solvent, voltage, agitation speed, extraction time, pH of the donor and acceptor phase and concentration of humic acids were investigated in detail. After extraction, the acceptor phase was collected and directly injected for capillary electrophoretic (CE) analysis. Combined with capacitively coupled contactless conductivity detection (C 4D), the direct detection of these compounds could be achieved. Moreover, large-volume sample injection was employed to further enhance the sensitivity of this method. Limits of detection (LODs) as low as ng/mL were reached for the studied analytes, with overall LOD enhancements of four orders of magnitude.