Contamination of surface and groundwater sources with pesticide residues has been of great concern for a long time and it is a major challenge for the preservation and sustainability of the environment. In order to accomplish the requirements of the European Directive 98/83/EC, we developed and validated an analytical method based on the combination of gas chromatography and tandem quadrupole mass spectrometry (GC-MS/MS) using solid-phase extraction as sample preparation. In this work nine pesticides were studied: molinate, simazine, atrazine, terbuthylazine, diazinon, alachlor, metalaxyl, metolachlor and pendimethalin. In order to get the best sensitivity and selectivity for each pesticide, several parameters of the tandem mass spectrometry were optimized using the MRM mode. Good linearity of the detector response was found for all pesticides at concentrations within the tested working range, with linear determination coefficients higher than 0.9988. Recoveries studies in several matrices with different fortification levels were performed, with recoveries between 77 and 115% with RSD lower than 9.5%. The MQLs obtained for these compounds were between 0.013 μg L−1 and 0.022 μg L−1, which were much lower than the maximum level established by the European legislation.
Keywords: gas chromatography, pesticides, tandem mass spectrometry, water