LC-MS/MS determination of pesticide residues in fruits and vegetables

The aim of the research is to evaluate pesticide residue contamination of fresh and frozen fruits and vegetables, agricultural raw material, purchased from Polish farmers for production of frozen fruits and vegetables, and the estimation of the multiresidue method effectiveness expressed as the proportion of pesticides detected in food samples to the total number of pesticides analyzed by multiresidue methods. A total of 144 samples (of black currants, red currants, raspberries, cherries, strawberries, blackberries, cauliflowers and broccoli) were analyzed using LC-MS/MS method for the determination of 60 pesticides. QuEChERS extraction, matrix-matched calibration and dynamic multiple reaction monitoring method were used. Residues of 15 compounds, mainly fungicides and insecticides, were detected in 46 samples. The percentage of samples with residues above the maximum residue levels (MRL) was 15%, whereas samples with residues below MRL were 17%. A total of 13 samples contained more than one pesticide residue. Pesticide residues were detected most often in samples of black currants (50%), broccoli (36.4%), raspberries (29%) and red currants (21.8%). The most frequently detected pesticides were carbendazim and acetamiprid. The proportion of pesticides detected during our study to the total number of analyzed pesticides amounted to 25%. It was compared to literature findings. For three fourth of multiresidue methods, the proportion was below 50% for methods developed for the analysis of less than 100 pesticides, and below 30% for methods developed for the analysis of more than 100 pesticides. It appears that a lot of efforts and means is lost on pesticides never or rarely detected in examined samples. The workload and cost effectiveness of the development and application of multiresidue methods along with the range of pesticides covered by the method should be carefully and thoroughly considered anytime when a new method or workflow is developed. Including non-targeted screenings in pesticide residue control seems to be an alternative worth considering.