Development of an efficient extraction method by combinating of QuEChERS–microwave-assisted dispersive liquid liquid microextraction using deep eutectic solvent; Application in extraction of some widely used pesticides from tomato samples

Pesticides such as insecticides, herbicides, fungicides, and acaricides are widely used during cultivation and post-harvest storage of crops. It is intended that their use to prevent the destruction of crops by controlling agricultural pests or unwanted plants and thereby improve food production [1, 2]. Although the use of pesticides in agricultural applications provides a wide range of beneficial effects, their misuse can result in unacceptable high levels of them in the products and also pollutes soil, air, and surface water. So, it is significant to develop a detection method with high sensitivity for evaluating food, water, and other environmental samples safety and possible risks to human health. In order to determine trace level of pesticide residues, an extraction and preconcentration step is necessary. Dispersive liquid–liquid extraction (DLLME) [3] is an important sample preparation method because of its simplicity, efficiency, and wide acceptance in many standard methods. In the present study, combination of QuEChERS-microwave-assisted DLLME/gas chromatography-flame ionization detection was investigated for the extraction, pre-concentration and determination of ten widely used pesticide residues in tomato samples. A mixture of a deep eutectic solvent (extraction solvent) and acetonitrile (disperser solvent) obtained from QuEChERS method was rapidly injected into the sample solution heated for 20s in microwave. Analytical parameters including enrichment factors (2150–2900), linearity (r 0.997), limits of detection (0.62–2.9 ng mL-1) and quantification (2.2– 7.5 ng.mL-1), relative standard deviations ( 7%) and extraction recoveries (43–58%) showed the high efficiency of the developed method for analysis of the target analytes. The proposed procedure was used effectively to analyze analytes in tomato samples, and metalaxyl and penconazole were found in tomato samples.