Development and validation of LC-MS/MS method for determining multi-residue pesticides in vegetables

This work describes the development and validation of a method using liquid chromatography with tandem mass spectrometry (LC-MS/MS) with electrospray ionization (ESI) for the determination of 17 pesticides in cauliflower and broccoli samples. Ten cauliflower and broccoli samples were obtained from a commercial establishment in Fortaleza-CE, Brazil. The pesticides were extracted using a Quenchers method. The method validation involved selectivity, matrix effect, linearity and statistical tests, limit of detection (LOD) and limit of quantification (LOQ), precision and accuracy. The method showed a good sensitivity, matrix effects, data heteroscedasticity, significance of R and slope of the curves. The method LODm was of 2.0 μg kg^-1. Precision reached ≤20% and accuracy ranged from 80 to 110% for medium concentration levels and from 70 to 120% for high concentration for most analytes, in accordance with pesticide residue guidelines. The acephate was detected in broccoli samples at level below the MRL established by EU (approximately 4.2 μg kg^-1).