Multiresidue Determination of Pesticides in Drinking Water by Gas Chromatography-Mass Spectrometry after Solid-Phase Extraction

In this work, a method using solid-phase extraction and gas chromatography coupled mass spectrometry in the selective ion monitoring (SIM) mode was developed and validated for the multi-class determination of 20 pesticides regulated by the Brazilian legislation for drinking water. Because these pesticides must be determined at low concentrations, a high preconcentration factor associated to the high sensitivity of chromatographic analysis was necessary. The method presented quantification limits between 0.003 and 0.093 mu g L-1. Most of the compounds presented mean recoveries between 51 and 116%. Although the differing chemical nature of the pesticides analyzed difficult the attainment of good recovery for all of the compounds evaluated, the precision of the results was excellent. The selectivity of the method was evaluated through the relative intensity of quantification and qualification ions and was considered adequate. Analysis in real samples met criteria for instrumental qualification and the system suitability evaluation.