Analysis of pesticides in fruit, vegetables and cereals using methanolic extraction and detection by liquid chromatography-tandem mass spectrometry

A method for analysing carbamates and other relatively polar pesticides by LC-MS-MS with electrospray ionisation has been developed. The method-is based on extraction by ultrasonication using a methanolic ammonium acetate-acetic acid buffer. After centrifugation the samples are filtered in Miniprep filter HPLC vials and detected by LC-MS-MS. To compensate for variations in the MS response [C-13(6)]-carbaryl was used as internal standard and matrix-matched pesticide solutions were used as external standards for the quantification. The method has been validated for the matrices apple, avocado, carrot, lettuce, orange, potato and wheat at the spiking levels-0.02; 0.04 and 0.20 mg kg(-1). Recoveries were generally in the range 70-120%. Results from participation in three intercomparisons proved the accuracy of the method. As the analytical procedure does not include any concentration or cleanup steps, it is easy and fast to perform, making it applicable for routine analysis in large pesticide monitoring programmes. (C) 2004 Elsevier B.V. All rights reserved.