Dispersive liquid–liquid microextraction combined with gas chromatography–electron capture detection for the determination of polychlorinated biphenyls in soils

In this article, dispersive liquid–liquid microextraction (DLLME) and gas chromatography–electron capture detection (GC–ECD) were presented for the extraction and determination of five polychlorinated biphenyls (PCBs) in soil samples. Acetone was used as extraction solvent for the extraction of PCBs from soil samples. In DLLME, the target analytes in the extraction solvent were rapidly transferred from the acetone extract to chlorobenzene when the extraction process began. The main advantages of this method are quick speed, high enrichment factor, high recovery and good repeatability. Under the optimum conditions, the method yields a linear calibration curve in the concentration range from 2 to 2000 μg kg−1for PCB 52, and 0.4 to 400 μg kg−1 for other target analytes. Coefficients of correlation (r2) ranged from 0.9993 to 0.9999. The repeatability was tested by spiking soil samples at a concentration level of 10 μg kg−1 for PCBs. The relative standard deviations (RSDs, n = 11) varied between 2.2% and 6.4%. The limits of detection (LODs), based on signal-to-noise (S/N) of 3, were between 0.20 and 0.50 μg kg−1. The relative recoveries of the five PCBs from soil S1, S2 and S3 at spiking levels of 10, 20 and 50 μg kg−1 were in the range of 88.70–103.8%, 82.50–106.3% and 82.30–113.6%, respectively. Therefore, DLLME combined with GC–ECD can be successfully applied for the determination of trace PCB residues in real soil samples.