Simultaneous determination of 45 pesticides in fruit and vegetable using an improved QuEChERS method and on-line gel permeation chromatography-gas chromatography/mass spectrometer.

In this study, a method was developed to determine 45 selected pesticides (of different chemical families) in fruit and vegetable (including apple, spinach and cucumber). Samples were extracted using an improved QuEChERS method with salting out and phase separation in two steps. The target pesticides in concentrated extracts were analyzed by an on-line gel permeation chromatography-gas chromatography/mass spectrometer (online-GPC-GC/MS). Online GPC effectively removed matrix interferences and greatly improved the method sensitivity, recoveries and automation. Method limits of quantification were 10 ng/g for uniconazole and metalaxyl, and 5 ng/g for other 43 target analytes. In three fruit and vegetable matrices each spiked with 45 pesticides (0.01 μg/g), mean recoveries ranged from 80 to 118% for most of the tested pesticides except for profenofos (77% in apple) and chlorpyrifos (68% in apple and 75% in cucumber), with relative standard deviations (RSDs) of less than 14%. The results of the proficiency testing showed that the method is very successful in measuring the certified pesticides with less than 1.3 of the absolute value of Z-score. This method has been applied for routinely monitoring pesticides in fresh fruit and vegetable.