Development of counter current salting-out homogenous liquid–liquid extraction for determination of some pesticides in fruit juice samples

Pesticides such as insecticides, herbicides, and fungicides are widely used during cultivation and post–harvest storages 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].In this study, a new extraction method based on counter current salting-out homogenous liquid–liquid extraction followed by dispersive liquid–liquid microextraction–solidification of floating organic droplet has been developed for the extraction and preconcentration of some widely used pesticides in fruit juice samples prior to their analysis by gas chromatography–flame ionization detection. In this method, initially sodium sulfate as a phase separation agent is filled into a column and a mixture of water (or fruit juice) and acetonitrile is passed through the column. By passing the mixture sodium sulfate is dissolved and the fine droplets of acetonitrile are formed due to salting-out effect. The produced droplets go up through the remained mixture and collect as a separate layer. Then, the collected organic phase (acetonitrile) is removed and mixed with menthol (extraction solvent at µL–level). In the second step, for further enrichment of the analytes the above solution is injected into de–ionized water placed in a test tube with conical bottom in order to dissolve acetonitrile into water and to achieve a sedimented phase at µL–level volume containing the enriched analytes. Under the optimal extraction conditions, the extraction recoveries and enrichment factors ranged from 82 to 93% and 3266–3728, respectively. Repeatability of the proposed method, expressed as relative standard deviations, ranged from 2–6% for intra– and inter–day precisions at a concentration of 30 µg L-1 of each pesticide. Limits of detection were obtained between 0.20 and 0.60 µg L-1.