Analysis of Phenolic Compounds by Ionic Liquid Based Liquid-Liquid Extraction Coupled with High Performance Liquid Chromatography

A method was investigated for the simultaneous determination of phenols in water by ionic liquid. 1-butyl-3-methylimidazolium hexafluorophosphate ([C-4 mim][PF6]) based liquid-liquid extraction coupled with high performance liquid chromatography. Some conditions that might affect the extraction efficiency such as pH value of aqueous phase, extraction time, volume of aqueous phase and salt concentration were optimized. The results indicated that the optinal conditions were pH 5.0, 40 min of extraction time, 60 mL of aqueous phase and no added salt, respectively. The enrichment factor of I [C-4 mim][PF6] for phenol, 4-nitro-phenol, 2-nitrophenol, 2,4-dimethylphenol and bisphenol A were compared with 1-octanol. Under the optimal conditions, the enrichment factor of ionic liquid for the five phenols were in the range of 9-151. The detection limits of phenol, 4-nitrophenoi, 2-nitrophenol, 2,4-dimethylphenol and bisphenol A were 2.0, 0.9, 0.3, 1.8 and 1.1 mu g/L (S/N=3), respectively. The proposed method was applied to the determination of the five phenols in tap, river, lake and waste water. Recoveries of the five phenols were in the range of 87.9% - 109.9%.