A simple multi-residue method for the determination of pesticides in fruits and vegetables using a methanolic extraction and ultra-high-performance liquid chromatography-tandem mass spectrometry: Optimization and extension of scope

• Optimized extraction with high speed disperser recovers systemic pesticides.
• Ten-fold dilution before injection reduces matrix effects.
• Water dilution before injection improves chromatography of the first eluting peaks.
• Recovery results for 200 pesticides demonstrate that the method is an alternative multi-residue method.

In 2004, a new multi-residue pesticides method had been published using methanol as extraction solvent. Our goal for this study was to optimize the analytical scheme while extending the compound scope from 19 to 200 pesticides. The main changes from the original method take place at the sample extraction and processing with a special attention to make the overall method fit for routine analysis with minimal cost. Hence, after a quick Ultra-Turrax homogenization with a methanolic solution, the sample is simply diluted before the separation and detection by ultra-high-performance liquid chromatography and MS/MS detection for quantitative and confirmatory purposes. The performance of the method including limits of quantification (LOQs), linearity, matrix effect, precision was evaluated during validation in accordance with the European Union SANCO/12571/2013 regulatory guidelines. Two representative matrices, lettuce and orange, were selected and fortified at two concentration levels for these experiments. At the LOQ and ten times the LOQ, recoveries of the analytes were mostly within 70–120%, with coefficients of variation lower than 25% in intra-day repeatability conditions. In addition to being simple and fast, these results demonstrate the suitability of the optimized method for the analysis of large scope pesticides in routine laboratories.