Application of QuEChERS Technique With UHPLC-Q-TOF Tandem Mass Spectrometry for High-Throughput Screening Multiple Pesticides in Food Matrixes Authors

With the implementation of strict regulations on the maximum allowable residue levels (MRLs) of pesticides in food matrixes worldwide, sensitive, reliable, and high-throughput analytical methodologies are urgently required for rapid screening and monitoring of the level of pesticide residues in foodstuffs. In this application note, we have detailed a method on QuEChERS extraction and cleanup protocol combined with ultra high performance liquid chromatography (UHPLC) quadrupole time-of-flight tandem mass spectrometry (Q-TOF-MS/MS) for multiple pesticides screening based on the work we published previously [1]. With optimized QuEChERS protocol, UHPLC-Q-TOF-MS/MS separation and detection conditions, we validated the analytical performance of the method by examining 281 pesticide compounds spiked into three representative matrixes of apple, tomato, and cabbage. The compounds were initially identified based on an accurate mass database with fixed retention time under the selected LC condition, and were further confirmed by matching their accurate Q-TOF MS/MS spectra against the established accurate MS/MS spectra library. The most abundant mono-isotopic ion species under TOF MS scanning mode was selected for quantitation. Using this method, all 281 pesticides spiked in the matrixes at primarily 5.0, 10.0, and 20.0 μg/kg were exclusively identified and quantified. A great majority (> 98%) of average recoveries (n = 5) were within the range of 70%~120% at the three spiked levels for all three matrixes. The relative standard deviations (RSDs) were lower than 20%. Using the matrix-matched calibration concentration primarily from 2.5 to 100.0 μg/kg, most compounds showed excellent linear responses, with correlation coefficients (R2) of 0.99 or above. Limits of detection (LOD) of these compounds in the three matrixes ranged from 0.010–4.5 μg/kg, which met the most strict requirement of EU regulations, with the MRLs of 10 μg/kg for most pesticide residues. The developed method has been successfully applied to screen the target pesticide residues in real samples; therefore it can be used as a routine monitoring method for these pesticide residues in food matrixes.