Dispersive liquid–liquid microextraction based on the solidification of floating organic droplet for the determination of polychlorinated biphenyls in aqueous samples

In the proposed method, an extraction solvent with a lower toxicity and density than the solvents typically used in dispersive liquid–liquid microextraction was used to extract seven polychlorinated biphenyls (PCBs) from aqueous samples. Due to the density and melting point of the extraction solvent, the extract which forms a layer on top of aqueous sample can be collected by solidifying it at low temperatures, which form a layer on top of the aqueous sample. Furthermore, the solidified phase can be easily removed from the aqueous phase. Based on preliminary studies, 1-undecanol was selected as the extraction solvent, and a series of parameters that affect the extraction efficiency were systematically investigated. Under the optimized conditions, enrichment factors for PCBs ranged between 494 and 606. Based on a signal-to-noise ratio of 3, the limit of detection for the method ranged between 3.3 and 5.4 ng L−1. Good linearity, reproducibility and recovery were also obtained.