Removal of triazole and pyrethroid pesticides from wheat grain by water treatment and ultrasound-supported processes.

A simple way to reduce pesticides in cereal grains is to use washing methods. The challenge of this study was to evaluate the effectiveness of reduction of 3 triazole fungicides (difenoconazole, tebuconazole, tetraconazole) and 3 pyrethroid insecticides (beta-cyfluthrin, cypermethrin, deltamethrin) commonly used in wheat protection. Four different pre-washing methods (hot and cold water washing, twice water, and ultrasound-supported washing) were evaluated. The processing factor (PF) was calculated based on the concentration of pesticides determined by LC-MS/MS in the samples of cereal grains before and after the washing process. PFs were within the range 0.01-0.97. Time, teperature and ultrasound were factors influencing the efficiency of water treatment. The study showed that ultrasound-supported washing eliminated pesticide residues to a greater extent than ordinary washing. This process significantly affected or completely reduced concentrations of triazoles in wheat grains. The highest reduction of residues (99%) was received for tebuconazole and ultrasound washing with heating temperature of 60 °C for a total of 10 min. In all washing processes, pyrethroids were removed with lower efficiency than triazoles. The lowest residue reduction was obtained for cypermethrin and washing under cold water for 5 min (3%; PF = 0.97). Beta-Cyfluthrin showed only a 6-27% reduction regardless of the process (PF: 0.73-0.95). Using static analysis, the relationship between the properties of pesticides and the reduction of their concentration in cereals was clarified and showed a strong correlation.