Quantification of pesticides in food crops using QuEChERS approaches and GC-MS/MS

The analysis of pesticides in food products requires accurate measurements for which standardised protocols have been developed. This paper reports the validation of QuEChERS (quick, easy, cheap, effective, rugged, and safe)-based methods applied to three different food samples (brown rice, red pepper and mandarin orange) analysed using gas chromatography-tandem mass spectrometry (GC-MS/MS). The validation of the analytical methods used to measure 113 pesticides, including various insecticides, fungicides and herbicides, was conducted in three food matrices and at three spiking levels by three different laboratories. The set of validated results was interpreted, statistically analysed and visualised using principal component analysis (PCA). Notably, the matrix effects in GC-MS analysis for most of the tested pesticides from different matrices were lowered to practical values (less than 30%) appropriate for routine analysis. This allowed for the quantification of pesticides in the samples using standard and analyte protectants (APs) in the reagent method blank as a screening measure, providing an alternative to matrix-matched calibration. Alternatively, the use of only one standardised calibration (grape matrix) in combination with APs also allowed for the qualitative and semi-quantitative analysis of pesticides in different matrices. The inclusion of APs reduced the differences in the matrix-induced enhancement effects of various samples. The use of an internal standard (IS) to correct the matrix effects was also noted. The normalisation of the analyte peak with triphenyl phosphate (TPP) as an IS resulted in a slight improvement of validation values such as precision and linearity in only one laboratory, but it lowered the value of matrix effects in all three laboratories.