[Low-density solvent-based solvent demulsification dispersive liquid-liquid microextraction combined with gas chromatography for determination of polycyclic aromatic hydrocarbons in water samples].

A novel method of low-density solvent-based solvent demulsification dispersive liquid-liquid microextraction (SD-DLLME) was developed for the determination of eight polycyclic aromatic hydrocarbons (PAHs) in water samples by gas chromatography-flame ionization detection (GC-FID). Conventional DLLME methods usually employ organic solvents heavier than water as the extraction solvents and achieve the phase separation through centrifugation. On the contrary, in this proposed extraction procedure, a mixture of low-density extraction solvent (toluene) and dispersive solvent (acetone) was injected into the aqueous sample solution to form an emulsion. A demulsification solvent (acetonitrile) was then injected into the aqueous solution to break up the emulsion, which turned clear quickly and was separated into two layers. The upper layer (toluene) was collected and analyzed by GC. No centrifugation was required in this procedure. Factors affecting the extraction efficiency such as the type and volume of dispersive solvent, extraction solvent and de-emulsifier were investigated in detail. Under the optimized conditions, the proposed method provided a good linearity in the range of 20 - 500 microg/L (r2 = 0.994 2 - 0.999 9). The limits of detection (S/N = 3) were in the range of 0.52 - 5.11 microg/L. The relative standard deviations (RSDs) for the determination of 40 microg/L PAHs were in the range of 2.2% - 13.6% (n = 5). The proposed method is fast, efficient and convenient. It has been successfully applied to the determination of PAHs in natural water samples with the spiked recoveries of 80.2% - 115.1%.