Sensitive determination of phenols from water samples by temperature-controlled ionic liquid dispersive liquid-phase microextraction

This paper established a new determination method for phenols using temperature-controlled ionic liquid dispersive liquid-phase microextraction prior to high-performance liquid chromatography. In this experiment, 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) was employed as the extraction solvent for the enrichment of 2-chlorophenol, 2-naphthol, 2,4-dinitrophenol, and 2,4-dichlorophenol. Parameters that may affect the extraction efficiency including the volume of [C8MIM][PF6], dissoluble temperature, extraction time, sample pH, amount of ethanol, centrifugation time and salting-out effect have been investigated in detail. Under the optimal conditions, they have good linear relationships over the concentration range of 1.0-100 ng mL-1 for 2-chlorophenol, 2-naphthol, 2,4-dinitrophenol, and 1.5-150 ng mL-1 for 2,4-dichlorophenol, and excellent detection sensitivity with limits of detection (LOD, S/N = 3) in the range of 0.27-0.68 μg L-1. Intra day and inter day precisions of the proposed method (RSDs, n = 6) were 2.1-3.7% and 5.1-7.2%, respectively. The proposed method has been successfully applied to analyze real water samples spiked with two different concentrations and good spiked recoveries over the range of 85.8-117.0% were obtained. These results indicated that the proposed method would be competitive in the analysis of phenols in the future.