Determination of carbamate and urea pesticide residues in fresh vegetables using microwave-assisted extraction and liquid chromatography

摘要

An analytical multiresidue method for the simultaneous determination of seven pesticides in fresh vegetable samples, namely, courgette (Cucurbita pepo),cucumber (Cucumis sativus), lettuce (Lactuca sativa, Romaine and Icebergvarieties) and peppers (Capsicum sp.) is described. The procedure, based onmicrowave-assisted extraction (MAE) and analysis by liquid chromatography–photodiode array (LC–PDA) detection was applied to four carbamates(carbofuran, carbaryl, chlorpropham and EPTC) and three urea pesticides(monolinuron, metobromuron and linuron). Extraction solvent and the additionof anhydrous sodium sulphate to fresh vegetable homogenate before MAE werethe parameters optimised for each commodity. Recovery studies were performedusing spiked samples in the range 250–403 µgkg- 1 in each pesticide. The pesticideresidues were extracted using 20mL acetonitrile at 60 ºC, for 10 min. Acceptablerecoveries and RSDs were attained (overall average recovery of 77.2% and RSDsare lower than 11%). Detection limits ranged between 5.8 µgkg- 1 for carbaryl to12.3 µgkg- 1 for carbofuran. The analytical protocol was applied for qualitycontrol of 41 fresh vegetable samples bought in Oporto Metropolitan Area(North Portugal). None of the samples contained any detectable amounts of thestudied compounds.