Assessment of pesticide residues in citrus fruit on the Czech market.

When assessing citrus fruit quality, besides natural health-promoting compounds, attention also has to be paid to residues of chemicals used to protect fruit against various pests. A set of 49 samples of different types of citrus fruits collected at the Czech market were analysed for 460 pesticide residues using LC-MS/MS and GC-MS/MS methods. While no residues were detected in citruses from organic farming, altogether 38 various pesticide residues were detected in conventional production samples. Buprofezin in two grapefruit samples and fenbutatin oxide in one tangerine sample exceeded maximum residue limits (MRLs). Depending on the pesticide group, 10-70% of residues were found in pulp, this means that their processing factors calculated for peeling are in the range of 0.02-0.76. In the case of a beverage prepared from unpeeled lemon slices, the transfer of residues from contaminated fruit into infusion was, depending on the beverage type and processing conditions, in the range of 8-61%.

Evaluation of Pesticide Residue Dynamics in Lettuce, Onion, Leek, Carrot and Parsley.

The dynamics of 32 active substances contained in pesticide formulations (15 fungicides and 17 insecticides) were analyzed in iceberg lettuce, onion, leek, carrot, and parsley. Pesticide residues were monitored from the time of application until harvest. In total, 114 mathematical models of residue dissipation were developed using a first-order kinetic equation. Based on these models, it was possible to predict the action pre-harvest interval (the time between the last pesticide application and crop harvest) needed to attain a targeted action threshold (value significantly lower than the maximum limit) for low-residue vegetable production. In addition, it was possible to determine an action pre-harvest interval based on an action threshold of 0.01 mg kg-1 to produce vegetables intended for zero-residue production. The highest amount of pesticide residues were found in carrot and parsley leaves several days after treatment, and pesticide dissipation was generally slow. Lower amounts were found in leeks and lettuce, but pesticide dissipation was faster in lettuce. According to our findings, it seems feasible to apply reduced pesticide amounts to stay below unwanted residue levels. However, understanding the effectivity of reduced pesticide application for controlling relevant pest organisms requires further research.