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

Abstract

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 Iceberg varieties) and peppers (Capsicum sp.) is described. The procedure, based on microwave-assisted extraction (MAE) and analysis by liquid chromatographyphotodiode 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 addition of anhydrous sodium sulphate to fresh vegetable homogenate before MAE were the parameters optimised for each commodity. Recovery studies were performed using spiked samples in the range 250-403 mg kg -1 in each pesticide. The pesticide residues were extracted using 20 mL acetonitrile at 60 o C, for 10 min. Acceptable recoveries and RSDs were attained (overall average recovery of 77.2% and RSDs are lower than 11%). Detection limits ranged between 5.8 mg kg -1 for carbaryl to 12.3 mg kg -1 for carbofuran. The analytical protocol was applied for quality control of 41 fresh vegetable samples bought in Oporto Metropolitan Area (North Portugal). None of the samples contained any detectable amounts of the studied compounds.

Urea Pesticides

“…They are also time-consuming and involve multistep processes that have always the risk of loss of some analytes. Supercritical-fluid extraction, matrix solid-phase dispersion, pressurized liquid extraction (Bichon et al, 2006), microwaveassisted extraction (Paiga et al, 2008(Paiga et al, , 2009aPaiga et al, 2009b) and batch extraction enhanced by sonication (Boti et al, 2007a;Buszewski et al, 2006;De Rossi & Desiderio, 2005) have been developed as alternative techniques to replace classical extraction methods mainly for solid samples. All these methods reduce extraction time and the volumes of solvent required, but some have the disadvantages of high investment and maintenance costs of the instruments (i.e., supercritical-fluid extraction, pressurized liquid extraction, and microwave-assisted extraction).…”

“…The major drawback of this procedure is the manual preparation which complicates the routine application (Bichon et al, 2006). Nowadays, microwave-assisted extraction and pressurised liquid extraction are applied successfully for urea residues control in soils (Paiga et al, 2008), vegetables (Paiga et al, 2009a;Paiga et al, 2009b) and in oysters (Bichon et al, 2006a). Low temperatures must be selected due to urea's thermolability.…”

Fe3O4 nanoparticles coated with polyhedral oligomeric silsesquioxanes and β‐cyclodextrin for magnetic solid‐phase extraction of carbaryl and carbofuran

“…The preconcentrated process converts the analyte into a form suitable for detection or isolation, conducing to eliminate potential interferences [7]. In comparison with traditional treatment methods of extraction for carbaryl and carbofuran, for example, LLE [8], MAE [9], and solid–liquid extraction [10], SPE [11–12] as the most common sample preparation method has some advantages of easy operation, high preconcentration factors, and low usage of organic solvents. And the nature of adsorbent has a vital role in the adsorption of analytes in the SPE technique.…”

Reversed Electrode Polarity Stacking Sample Preconcentration Combined with Micellar Electrokinetic Chromatography for the Analysis of Carbamate Insecticide Residues in Fruit Juices

“…A common system available in most laboratories, HPLCphotodiode array (PDA) detection, is a popular method for the analysis of carbamates after suitable sample preparation techniques such as micro-solid-phase extraction (Basheer et al 2009), dispersive liquid-liquid microextraction (Wu et al 2009;Liu et al 2009), and microwave-assisted extraction (Paíga et al 2009(Paíga et al , 2008. Although HPLC is a selective and sensitive method, it often requires long analysis time, consumes large volumes of organic solvents, and has a relatively high cost.…”