Development, validation and application of a SDME/GC-FID methodology for the multiresidue determination of organophosphate and pyrethroid pesticides in water

A single-drop microextraction (SDME) procedure was developed for the analysis of organophosphorus and pyrethroid pesticides in water by gas chromatography (GC) with flame ionization detection (GC-FID). The significant parameters that affect SDME performance, such as the selection of microextraction solvent, solvent volume, extraction time, and stirring rate, were studied and optimized using a tool screening factorial design. The limits of detection (LODs) in water for the four investigated compounds were between 0.3 and 3.0 mu g L-1, with relative standard deviations ranging from 7.7 to 18.8%. Linear response data were obtained in the concentration range of 0.9-6.0 mu g L-1 (X-cyhalothrin), 3.0-60.0 mu g L-1 (methyl parathion), 9.0-60.0 mu g L-1 (ethion), and 9.0-30.0 mu g L-1 (permethrin), with correlation coefficients ranging from 0.9337 to 0.9977. The relative recoveries for the spiked water ranged from 73.0 to 104%. Environmental water samples (n = 26) were successfully analyzed using the proposed method and methyl parathion presented concentration up to 2.74 mu g L-1. The SDME method, coupled with GC-FID analysis, provided good precision, accuracy, and reproducibility over a wide linear range. Other highlights of the method include its ease of use and its requirement of only small volumes of both organic solvent and sample. (C) 2009 Elsevier B.V. All rights reserved.