Safety control of fruit and vegetable products: determination of residual amounts of a fungicide of the phthalimide class – captan

Introduction. Due to the widespread use of captan-based fungicides, the substance is among the top of 100 pesticides most frequently detected in food products worldwide. Captan is hydrolytically unstable and rapidly degrades to the metabolite 1,2,3,6-tetrahydrophthalimide (THPI). The substance tends to degrade at various stages of analysis, which justified the need for special experiments. Purpose of the work. Conducting experimental studies to assess the potential risks of obtaining incorrect analytical results on the actual content of captan and THPI in food products when assessing its safety to substantiate optimal approaches to the analysis procedure and develop a methodology for controlling the content of captan and its metabolite tetrahydrophthalimide in fruit, vegetable, and juice products. Materials and methods. For the identification and quantitative determination of substances, the method of high performance liquid chromatography with a triple quadrupole mass detector (HPLC-MS/MS) was used. To extract analytes from a homogenized sample, acetonitrile containing 0.1% formic acid was used. An aliquot of the extract was purified by freezing at minus 18 °C. Results. In the studied samples of citrus, the analytes showed stability. Thirty months after storage of samples in deep freezing conditions (temperature not higher than –20 °C), the identified levels of active ingredients of the pesticides imazalil, pyrimethanil, and prochloraz did not change by more than 20% compared to the previously detected concentrations. Insignificant amounts of imidacloprid, thiabendazole and pyriproxyfen, traces of azoxystrobin and trifloxystrobin, detected in the study of samples, were also found in samples after long-term storage. Limitation. The study did not look at food products with a low water content. Conclusion. For a correct assessment of food safety, it t has been shown to be necessary to quantify captan together with its metabolite THPI. It has been experimentally substantiated that lowering the pH and temperature during the preparation and storage of samples and extracts makes it possible to retain captan in the sample. A procedure has been developed for determining the residual amounts of captan and its metabolite tetrahydrophthalimide in fruit, vegetable, and juice products by HPLC-MS/MS in the range of 0.01–50 mg/kg.