Analysis of 140 pesticides from conventional farming foodstuff samples after extraction with the modified QuECheRS method

Pesticides in foodstuff are becoming a major issue due to their intensive use in agriculture. Thus an appropriate control of their residues in food samples has to be operated. In this study we analysed 105 pesticides with GC/SQ-MS and 46 pesticides with HPLC/IT-MS after extraction with the QuECheRS method in four matrices (grape, lemon, onion and tomatoes). For GC-amenable substances, the LOD and LOQ ranged from 0.4 to 48.2 mu g/kg and from 1.2 to 161 mu g/kg, respectively. For HPLC-amenable substances, they varied from 1.0 to 115 mu g/kg and from 3.3 to 382 mu g/kg, respectively. With GC/MS, 61-82% of the substances showed a recovery in the range of 701 110% and 6-30% presented a recovery higher than 110% at the 500 mu g/kg fortification level. With HPLC/MS, 87-93%, of the substances presented recoveries in the range of 70-110% at the 500 mu g/kg fortification level compared to 78-85% at the 50 mu g/kg fortification level. Lemon and onion showed poor recoveries but are known to be difficult matrices (high acidic and high sulfur content, respectively). The method was proved to be repeatable with RSD lower than 20% at 500 mu g/kg and lower than 15% at 50 mu g/kg with both devices. (C) 2007 Elsevier Ltd. All rights reserved.