Qualitative and quantitative analysis of polar pesticide multiresidues in leaf samples with a liquid chromatography–ion-trap mass-selective detector

Abstract

Since 1995, in Austria, an agricultural programme (ÖPUL) has promoted an environmentally friendly and extensive production with restricted pesticide use. To observe the achievement of this goal, the pesticides in leaf samples are monitored. This study aimed to develop a multiresidue method for the qualitative and quantitative analysis of 46 pesticides in leaf samples with HPLC-IT-MS equipped with an electrospray ionization in positive mode after extraction with the QuECheRS method. The method has been validated for leaf samples based on the SANCO European Guideline at two fortification levels (LOQ and 10 times LOQ). The recoveries of the pesticides, with a few exceptions, were between 70 and 110% at both fortification levels and modes (full scan and selected reaction monitoring, SRM) with acceptable precision (RSD < 16%). For most pesticides, the method was linear over two orders of magnitude, repeatable, and accurate. Although the matrix effect was relevant for only a few pesticides, matrix-matched standards were used. The quantification of real samples in both modes fitted well, but a confirmation in the SRM mode was always necessary to avoid false-positive samples. Unfortunately, the method is not yet sensitive enough for organic farming foodstuff, since the limits of detection and quantification are still too high (between 1.5 and 218 µg kg−1 and between 4.8 and 725 µg kg−1 in full scan, respectively) compared with the Austrian authorized value of 100 µg kg−1 fresh leaf sample defined in the ÖPUL programme.