Surveillance of fungicidal dithiocarbamate residues in fruits and vegetables

Derivatisation, solid–liquid extraction, solid-phase purification and HPLC–DAD separation is a simple, fast, and accurate method developed for the determination of dithiocarbamate (DTC) fungicides in fruits and vegetables. Quantification is based on external standard calibration curves made with DTCs-spiked blank-matrices. Limits of detection (LODs) and limits of quantitation (LOQs) are in the range of 0.01–0.3 and 0.02–0.5 mg/kg, respectively. Recoveries higher than 78% were obtained for the target DTCs in all the commodities studied. The aim of this research was to evaluate the quality and determine the concentrations of DTC fungicide residues in plant material harvested from September to November of 2010. Several fruits and vegetables produced in Spain were collected at small shops and large food chains distributed by the four provinces of Galicia (North-Western Spain). In total, 150 samples were studied (32 apples, 12 wine grapes, 32 lettuces, 32 peppers, 32 tomatoes, and 10 strawberries). Residues of DTCs were found in all the products analysed with the exception of strawberries, being ethylenebis(dithiocarbamates) (EBDCs) vs. propylenebis (dithiocarbamates) (PBDCs) the main contributors to the total pesticide load. Moreover, fungicide residues exceeding maximum residue limits (MRLs) were identified in 6% of the samples analysed, specifically on lettuces and peppers.