Ionic liquid-based dispersive liquid-liquid microextraction with back-extraction coupled with capillary electrophoresis to determine phenolic compounds

Ionic liquid (IL) based dispersive liquidliquid microextraction (DLLME) with back-extraction coupled with capillary electrophoresis ultraviolet detection was developed to determine four phenolic compounds (bisphenol-A, beta-naphthol, a-naphthol, 2, 4-dichlorophenol) in aqueous cosmetics. The developed method was used to preconcentrate and clean up the four phenolic compounds including two steps. The analytes were transferred into room temperature ionic liquid (1-octyl-3-methylimidazolium hexafluorophosphate, [C8MIM][PF6]) rich-phase in the first step. In the second step, the analytes were back-extracted into the alkaline aqueous phase. The effects of extraction parameters, such as type and volume of extraction solvent, type and volume of disperser, extraction and centrifugal time, sample pH, salt addition, and concentration and volume of NaOH in back-extraction were investigated. Under the optimal experimental conditions, the preconcentration factors were 60.1 for bisphenol-A, 52.7 for beta-naphthol, 49.2 for a-naphthol, and 18.0 for 2, 4-dichlorophenol. The limits of detection for bisphenol-A, beta-naphthol, a-naphthol and 2, 4-dichlorophenol were 5, 5, 8, and 100 ng mL-1, respectively. Four kinds of aqueous cosmetics including toner, soften lotion, make-up remover, and perfume were analyzed and yielded recoveries ranging from 81.6% to 119.4%. The main advantages of the proposed method are quick, easy, cheap, and effective.