Iceberg lettuce is one of the most consumed leafy vegetables, which is often treated by different pesticides against pests and diseases. The aim of this study was to describe the fate of 25 pesticides (16 fungicides, 7 insecticides and 2 herbicides) based on quantitative analysis of the parent compounds and targeted screening of their (bio)transformation products. Mathematical models describing a decrease in pesticide residue levels were proposed for 24 pesticides using a first-order kinetic equation. These models provide the data needed to predict consumer exposure associated with the consumption of conventionally grown iceberg lettuce. At harvest, concentrations of most pesticides were dropped under the established EU maximum residue levels, except for flonicamid, fluazifop and pyriproxyfen. A total of 113 pesticide metabolites and degradation products were detected and tentatively identified in extracts prepared by an optimized extraction procedure, i.e., the acidified QuEChERS method. Several products of reactions such as hydrolysis, dealkylation, dehalogenation and/or oxidation-reduction, originated either from various physicochemical processes, or within Phase I pesticide metabolism were detected. Additionally, numerous conjugates with hexose, malonic acid or acetic acid formed during PhaseII of pesticide metabolism were found. In this way, a deeper understanding of specific pesticide degradation mechanisms is facilitated. In addition, it is easier to track the history of pesticide treatment.
Pesticide residues from the time of application until harvest were analysed for 20, 17 and 18 active insecticidal and fungicidal substances in Chinese cabbage, head cabbage and cauliflower, respectively. In total, 40 mathematical models of residue degradation were developed using a first-order kinetic equation, and from these models it was possible to forecast the action pre-harvest interval for a given action threshold for low-residue production in Brassica vegetables as a percentage of the maximum residue level. Additionally, it was possible to establish an action pre-harvest interval based on an action threshold of 0.01 mg kg(‒1) for the production of Brassica vegetables for baby food. Among the evaluated commodities, the speed of residue degradation was highest in head cabbage, medium in Chinese cabbage and lowest in cauliflower. The half-lives of pesticide in various vegetables were also determined: they ranged from 1.55 to 5.25 days in Chinese cabbage, from 0.47 to 6.54 days in head cabbage and from 1.88 to 7.22 days in cauliflower.
- MeSH
- Brassica chemie MeSH
- kontaminace potravin analýza MeSH
- průmyslové fungicidy analýza MeSH
- rezidua pesticidů analýza MeSH
- tandemová hmotnostní spektrometrie MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Čína MeSH
