ONLINE DETERMINATION OF ORGANOPHOSPHORUS PESTICIDES IN WATER BY SOLID-PHASE MICROEXTRACTION AND GAS-CHROMATOGRAPHY WITH THERMIONIC-SELECTIVE DETECTION

This paper describes the extraction of 49 organophosphorus pesticides (OPPs) from water samples using solid-phase microextraction (SPME). Th ree fibers, including a 15-mu m XAD-coated fiber, a 85-mu m polyacryla te-coated fiber, and a 30-mu m polydimethylsiloxane-coated fiber (PDMS ), were evaluated here. The effects of stir ring and the addition of N aCl to the sample were examined for the polyacrylate-coated fiber. The precision of the technique was examined for all three fibers and the extraction kinetics were investigated using the XAD-and polyacrylate-c oated fibers. With some exceptions, the XAD-and polyacrylate-coated fi bers performed better than the PDMS-coated fiber. The superiority of t he XAD-and polyacrylate-coated fibers over the PDMS-coated fiber can b e attributed to the aromatic functionalities of the XAD and the polar functionalities in the polyacrylate. The relatively high percent RSDs indicate that the SPME technique needs to be further refined before it can be used for anything other than screening. A more effective form of agitation than mechanical stirring may be necessary to reduce varia bility and achieve a faster equilibrium between the sample and the SPM E fiber.