Determination of polycyclic aromatic hydrocarbons in water samples by temperature-controlled ionic liquid dispersive liquid-liquid microextraction combined with high performance liquid chromatography

The present study describes a simple and sensitive method for the determination of polycyclic aromatic hydrocarbons (PAHs) in water samples by temperature-controlled ionic liquid dispersive liquid-liquid microextraction prior to high performance liquid chromatography with an ultraviolet detector. Three ionic liquids including 1-hexyl-3-methylimidazolium hexafluorophosphate [C6MIM][PF6], 1-benzyl-3-methylimidazolium hexafluorophosphate [C7MIM][PF6] and 1-octyl-3-methylimidazolium hexafluorophosphate [C8MIM][PF6] were investigated for enrichment, and the experimental results indicated that the best extraction efficiencies were achieved when [C8MIM][PF6] was used as the extraction solvent. Other factors affecting the extraction efficiency such as the volume of ionic liquid, heating temperature, extraction time, addition of 2-propanol, centrifugation time and ionic strength were also optimized. Under the optimal conditions, the detection limits of PAHs were in the range of 0.0005-0.88 mg L-1. The intra-day and inter-day precisions of the proposed method (RSDs, n = 6) were in the range of 2.7-7.4% and 5.5-11.4%, respectively. The proposed method was applied to the analysis of real environmental water samples and good spiked recoveries in the range of 83.5-118% were achieved. All these results indicate that the proposed method is a viable alternative to existing methods and would be very useful in the future.