Pseudo Peak Phenomena in Micellar Electrokinetic Capillary Chromatography by Using Ionic Surfactant

The origin of pseudo peak was studied by means of micellar electrokinetic capillary chromatography with cetyltrimethylaminium bromide as the pseudo stationary phase. It has been pointed that two peaks may appear for one component under certain conditions. Experiments showed that the relative areas of the two peaks of analyte depended on the time and the temperature of reaction between analyte and surfactant, and the concentration of surfactant in the sample solution. It means that the interaction between the analyte and the surfactant is a slow process, and a stable substance can be produced from the interaction. It is the substance and the analyte that may lead to the formation of two peaks. The fast interaction mechanism between the solute and the micellar should be queried from the experiment result.

Separation of Aniline Derivatives by Micellar Electrokinetic Capillary Chromatography

A micellar electrokinetic capillary chromatography (MECC) was developed for the determination of aniline and 6 substituted anilines. The seven components were separated within 25 min in the buffer solution of 40 mmol/L sodium borate and 100 mmol/L SDS. It was found that the separation was dependent on operating voltage, pH value, borate and SDS concentrations. The analytical performance was examined in terms of linear response and reproducibility. Wastewater was determined by the established method.

Determination of phenolic whitening agents in cosmetics by micellar electrokinetic capillary chromatography with amperometric detection

A sensitive method for simultaneous determination of six phenolic whitening agents, including arbutin, phenol, resorcinol, hydroquinone, kojic acid, and salicylic acid in cosmetics has been developed using micellar electrokinetic capillary chromatography with amperometric detection （MECC-AD）. Effects of several factors, such as the pH value and concentration of running buffer, potential applied to the working electrode, separation voltage, and injection time were investigated to obtain optimum conditions for separation and detection. With a 75 cm long fused-silica capillary tube, well-defined separation of six phenolic compounds was achieved in 10 mmol/L SDS/40 mmol/L H3BO3-Na2B407 running buffer （pH 9.0）. Good linear relationship was obtained for each analyte over three orders of magnitude with correlation coefficients （r2） between 0.9985 and 0.9994, and the detection limit （S/N = 3） ranged from 0.04 p^g/mL to 0.45 p^g/mL. The proposed method has been successfully applied for the determination of phenolic whitening agents in real cosmetic samples with satisfactory results, providing an alternative monitoring method for cosmetics safety regulation.

Optimization of micellar electrokinetic capillary chromatography method using central composite design for the analysis of components in Yangwei granule

Central composite design(CCD),together with multiple linear regression,was successfully used to optimize the electrophoretic buffer system of micellar electrokinetic capillary chromatography(MEKC) for the determination of albiflorin,paeoniflorin,liquiritin,and glycyrrhizic acid in the traditional Chinese medicine(TCM) prescription,Yangwei granule.Concentrations of sodium deoxycholate(SDC) and borate,and proportions of ammonia,acetonitrile,and methanol were optimized.The total resolutions of peaks between the analytes and their adjacent peaks in real samples were integrated into the evaluation index of separation efficiency.The optimum electrophoretic buffer contained 80 mmol/L SDC,20 mmol/L borate,5%(v/v) methanol,0.5%(v/v) ammonia,and 5%(v/v) acetonitrile.The correlation coefficients(R 2 ) between the peak areas and the corresponding concentrations of analytes were greater than 0.9956.The limits of detection(LODs) (S/N=3) of the analytes were 0.97-4.00μg/ml.The results indicate the superiority of CCD in optimizing the separation conditions of complex samples such as TCM prescriptions.