Ionic Liquid-based Dispersive Liquid-Liquid Microextraction Coupled With Capillary Electrophoresis To Determine Organic Pollutants And Pharmaceuticals

Capillary electrophoresis (CE) has been acknowledged a powerful separationtechnique due to its major merit of high resolution, small sample size, short analysistimes, extremely low solvent consumption and low operational costs. While it offers afew advantages, the main drawback of CE is the low detection limits in mostuniversally used UV detection. Thus, for determination the compounds in trace byCE-UV, it requires a sample preconcentration method. Dispersive liquid-liquidmicroextraction (DLLME), a new mode of LPME, was first introduced by Rezaeeet al. in2006, which with the merit of easy, fast, low cost, high preconcentrationfactor, and repeatability. It has been successfully used in the extraction of organic andinorganic compounds from solid and liquid samples. In DLLME, chosen a suitableextraction solvent plays an important role in obtaining good recoveries and highenrichment factors. Compared with the traditional extracting agent, room temperatureionic liquids (RTILs), which are regarded as green solvents, draw a great interest asthe extraction solvent in DLLME due to its interesting property of tunability. Theviscosity and surface tension of ILs can be easily manipulated, which make the ILshave the ability to form more stable and larger droplets. Furthermore, ILs can beeasily synthesized to be not only hydrophobic or hydrophilic but also miscible orimmiscible with the disperser solvent. And their high density is facilitated to the phase separation. This paper is focused on the application of IL-DLLME combined with CEto determine organic pollutants and pharmaceuticals in waters and cosmetics. Itcontains of the following two sections.1、IL-DLLME coupled to NaOH back-extraction has been developed to determinefour phenolic compounds (bisphenol-A, β-naphthol, α-naphthol,2,4-dichlorophenol)in aqueous cosmetics. The developed extraction method is including two steps:1) theanalytes are transferred into room temperature ionic liquid rich phase;2) the analytesare back-extracted into the alkaline aqueous phase. The reasons for using DLLMEwith back-extraction to determine these phenolic compounds can be shown as follows:[C8MIM][PF6] is too viscous to directly injection for CE and has strong UVabsorption at detection wavelength; the high concentration of IL injected into CE ispossibly attached to the inner surface of separation capillary. Through the secondextraction, some substances do not dissolve in alkaline aqueous phase will beremoved and the interferences from the sample matrix can also be decreased to acertain extent. The effects of extraction parameters have been investigated. Theoptimum conditions are as follows:80μL [C8MIM][PF6](as extraction solven);900μL acetone (as disperser);4000rpm,5min (centrifugal time);10%NaCl (m/v)(salt addition);150μL of0.1mol/L NaOH (back-extraction conditions). Under theoptimal experimental conditions, the limits of detection are5-100ng/mL (S/N=3) andthe preconcentration factors are18.0-60.1. Four kinds of aqueous cosmetics includingtoner, soften lotion, make-up remover and perfume were analyzed and yieldedrecoveries ranging from81.6%to119.4%. The main advantages of the proposedmethod are fast, simple, cheap and effective.2、DLLME coupled to CE has been developed to determine four glucocorticoid(triamcinolone, cortisone, hydrocortisone, dexamethasone) in water samples. Theseparation conditions have been investigated. The optimal conditions are20mmol/Lammonium acetate,20mmol/L sodium taurocholate hydrate,15mmol/L sodiumdodecyl sulfate and pH9.7. The effects of extraction parameters also have beeninvestigated, including type and volume of extraction solvent, type and volume ofdisperser, extraction and centrifugal time, sample pH, salt addition and concentration. Under the optimal experimental conditions, the limits of detection for triamcinolone,cortisone, hydrocortisone, and dexamethasone are0.1,0.2,0.4, and0.05μg/mL(S/N=3) respectively. The preconcentration factors are12.2for triamcinolone,14.8for cortisone,15.2for hydrocortisone, and39.7for dexamethasone. Tap water, riverwater and industrial sewage have been analyzed and yielded recoveries ranging from85.1%to111.6%.