Application of single-drop microextraction coupled with gas chromatography for the determination of multiclass pesticides in vegetables with nitrogen phosphorus and electron capture detection

In the present work the single-drop microextraction (SDME) technique coupled with GC-NPD and GC-ECD was evaluated for the determination of multi-class pesticides in vegetables. The donor sample solution preparation was optimized by testing different mixtures of solvents and dilutions with water. The SDME procedure was optimized by controlling drop organic solvent, drop volume, agitation, and exposure time. The optimum sample preparation was achieved with the use of a mixture of acetone/H2O (10/90, v/v) in donor sample Solution preparation and the consequent SDME using a toluene drop under mild stirring for 25 min. The efficiency of the extraction process was studied in fortified tomato and courgette samples and matrix effects were further estimated. The proposed method showed good linearity, limits of detection at the sub-mu g kg(-1) level and high precision (RSD <15%) and was applied with success in real vegetable samples showing that SDME can be a promising way for sample preparation in pesticide residue analysis. (C) 2008 Elsevier B.V. All rights reserved.