Development of counter current salting-out homogenous liquid–liquid extraction for isolation and preconcentration of some pesticides from aqueous samples

• A new version of SHLLE has been developed.
• The method is applied for the analysis of pesticide residues in fruit juices.
• LODs are achievable at μg L−1 using GC–FID.
• The method has high EFs and ERs, low LODs, and short extraction time.

In this paper, a new version of salting-out homogenous liquid–liquid extraction based on counter current mode combined with dispersive liquid–liquid microextraction has been developed for the extraction and preconcentration of some pesticides from aqueous samples and their determination by gas chromatography–flame ionization detection. In order to perform the method, aqueous solution of the analytes containing acetonitrile and 1,2-dibromoethane is transferred into a narrow bore tube which is filled partially with NaCl. During passing the solution through the tube, fine droplets of the organic phase are produced at the interface of solution and salt which go up through the tube and form a separated layer on the aqueous phase. The collected organic phase is removed and injected into de-ionized water for more enrichment of the analytes. Under the optimum extraction conditions, the method shows broad linear ranges for the target analytes. Enrichment factors and limits of detection for the selected pesticides are obtained in the ranges of 3480–3800 and 0.1–5 μg L−1, respectively. Relative standard deviations are in the range of 2–7% (n = 6, C = 50 or 100 μg L−1, each analyte). Finally, some aqueous samples were successfully analyzed using the developed method.

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