Processing factors and variability of pyrimethanil, fenhexamid and tolylfluanid in strawberries

An HPLC-MS/MS method for the analysis of three pesticides in strawberries was developed and validated. Recoveries were measured at three spiking levels and ranged from 85 to 99% (mean recoveries). The effects of processing of strawberries ranging from rinsing to jam production were investigated for the three fungicides tolylfluanid, fenhexamid and pyrimethanil, which were applied under field conditions. Kresoxim-methyl was also applied in the field, but was not found in any of the samples investigated. The effect of parameters such as preharvest interval, dose, harvest time and observed pesticide concentration after harvest (initial concentration, mg kg(-1)), were examined with respect to possible reduction of the pesticides. The results from rinsing showed that all three pesticides were reduced on average by 37% for tolylfluanid, by 34% for fenhexamid and by 19% for pyrimethanil. For tolylfluanid and fenhexamid, the initial concentration significantly affected the reduction. For fenhexamid, dose could also have a minor influence on reduction. For pyrimethanil, none of the parameters significantly influenced the reduction. For jam production, cooking significantly reduced tolylfluanid by an average of 91%. For fenhexamid and pyrimethanil, a smaller reduction was seen, 25% and 33%, respectively. The reduction of tolylfluanid and pyrimethanil was affected by the preharvest interval, while fenhexamid was affected by the initial concentration. The unit-to-unit variability of fungicide contents was also investigated and the variability factors for the three fungicides were from 1.9 to 2.8.