An effective multi-residue pretreatment technique, solid-phase extraction (SPE) combined with dispersive liquid-liquid microextraction (DLLME), was proposed for the trace analysis of 14 polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in milk samples using gas chromatography-mass spectrometry (GC-MS). Interesting analytes in milk samples were extracted with hexane after protein precipitation. The hexane extracts were loaded on an LC-Florisil column to isolate analytes from the milk matrix. The elutes were dried and dissolved in acetone, which was used as the disperser solvent in subsequent DLLME procedures. The effects of several important parameters on the extraction efficiency were evaluated. Under the optimized conditions, a linear relationship was obtained in the range of 0.02-10.00 μg/L (PCBs) and 0.5-100.00 μg/L (PBDEs). The LOD (S/N=3) and relative standard deviations (RSDs, n=5) for all analytes were 0.01-0.4 μg/L and 0.6-8.5%, respectively. The recoveries of the standards added to raw bovine milk samples were 74.0-131.8%, and the repeatabilities of the analysis results were 1.12-17.41%. This method has been successfully applied to estimating PCBs and PBDEs in milk samples.

We report a multi-residue pretreatment technique, termed temperature-assisted ionic liquid dispersive liquidliquid microextraction, and demonstrate its application to simultaneous extraction of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). An ionic liquid was used as the extraction solvent and dispersed into the liquid sample (water, urine) with the help of methanol and at elevated temperature. Parameters such as extraction solvent and its volume, disperser solvent and its volume, extraction time, centrifugation time, salt addition, extraction temperature and sample pH were optimized. Under the optimized conditions, an up to 278-fold enrichment factor and an >83.4% extraction recovery were obtained. A linear relationship is obtained in the range of 0.5-500 ng mL −1 . The limits of detection (at S/N03) and relative standard deviations (for n05) range from 0.1 to 0.4 ng mL −1 and from 1.0% to 5.6%, respectively. The recoveries for water and urine samples additionally spiked with PCBs and PBDEs are between 81.0 and 127.1% and 84.0 and 110.3%, respectively. The method was successfully applied to the determination of PCBs and PBDEs in real river water and in human urine samples.

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