Determination of pesticides in vegetables using large-volume injection column liquid chromatography-electrospray tandem mass spectrometry

Direct injection of a large volume (900 mu l) of a sample extract onto a li quid chromatographic (LC) column, LC separation and electrospray tandem mas s spectrometric detection were used for the quantitative analysis of a wide polarity range of pesticides in carrots and potatoes. Rapid sample prepara tion involved extraction of a small amount of sample (2 g) with a small vol ume of organic solvent (3 ml), clean-up over a filter and dilution of the o rganic extract with the aqueous LC eluent. The extraction efficiency for th e selected pesticides was studied using methanol, acetone and acetonitrile as solvents. Evaluation of the performance of the overall method, using ext raction with acetonitrile and detection in the selected-reaction-monitoring mode, showed excellent linearity in the range of 2-100 mu g/kg with limits of detection of 0.5-2 mu g/kg for both types of vegetable. With relative s tandard deviations of the MS peak area measurements of less than 6.5% (n=8) the repeatability of the method was fully satisfactory. (C) 2000 Elsevier Science B.V. All rights reserved.