Validation of a modified QuEChERS method for the determination of 167 pesticides in milk and milk products by LC-MS/MS

Abstract

A liquid chromatography tandem mass spectrometry (LC-MS/MS) method with modified QuEChERS (quick, easy, cheap, effective, rugged and safe) extraction cleaning process was comprehensively validated for determination of 167 pesticide residues in three matrices: milk, cheese and cream. Optimisation of the mass spectrometry parameters was performed by injecting pesticide standard solutions into the electrospray ion (ESI) source. The mass spectrometer was operated in the positive ESI mode. The validation data fulfilled the requirements of the European SANTE/11945/2015 Guideline. The specificity of the developed method is considered satisfactory. Good linearity (R 2 > 0.99) was obtained for all pesticide matrix calibration curves within the range of 0.1–100 μg kg−1. Mean recoveries of all target analytes ranged from 80.4 to 117.3%, and limits of quantification (LOQ) ranged from 1.1 to 13.1 μg kg−1, depending on pesticide residues. The repeatability and within-laboratory reproducibility ranged from 0.2 to 15.1% and from 1.3 to 19.4%, respectively. The uncertainty was not higher than 48% for target analytes in the three matrices. The validated method was successfully applied to screening of milk and milk products, and none of the 167 pesticides investigated was detected in 92 real samples.