On-Line Preconcentration Methods Research Of Microemulsion Capillary Electrophoresis Determine Glucocorticoids In Cosmetics

Glucocorticoids are a category of highly hydrophobic compounds that have anti-infective, anti-allergy effects. Adding glucocorticoids to cosmetics results in whitening and moisturizer effects. However, abusing cosmetics with corticosteroids contributes to many side effects. Until now, several analytical methods for the determination of glucocorticoids in cosmetics have been reported. However, the detection limit of these methods was too high to detect glucocorticoids especially in cosmetics that contain trace glucocorticoids. Thus, it is important to develop a fast and effective analysis of the glucocorticoids in the cosmetic industry. The main contents are shown as follows:1. Two on-line pre-concentration techniques including field-amplified and sweeping by β-cyclodextrin-microemulsion electrokinetic chromatography method were used to analyze Prednisone acetate, Prednisolone acetate, Hydrocortisone acetate in cosmetics. The running buffer was composed of SDS 2.8%(w/w), octane 1.0%(w/w), 1-butanol 5.6%(w/w), 10 mmol β-cyclodextrin, 40 mmol/L phosphate buffer(pH=2.8). The conditions of sample injection was 18.4 kPa×80s, respectively. Separating voltage was-20 kV. The detection wavelength was set at 250 nm. Under the optimum conditions, this present focusing technique improved the sensitivity enhancement by 586-fold, 579-fold, 529-fold for Prednisone acetate, Prednisolone acetate, Hydrocortisone acetate, respectively. The limit of detections were 12-19 μg/L(S/N=3). The developed method was used to analyze the glucocorticoids in cosmetics. The recoveries ranged from 92.5% to 107.5%. The RSD values(n=6) were less than 3.5%. The entire analysis process was completed in 14 min. It is obvious that the developed method could be used for the determination of glucocorticoids in cosmetics.2. A simple and efficient online sample pre-concentration method that combines sweeping in a reduced electric field by microemulsion electrokinetic chromatography(MEEKC) was developed for the determination four glucocorticoids(Prednisone, Hydrocortisone, Prednisolone and Betamethasone) in cosmetics. The running buffer was composed of 2.4%(w/w) dodecyl sodium sulfate, 0.8%(w/w) octane, 6.6%(w/w) 1-butanol,30 mmol/L borate buffer(pH=8.2). The separation voltage was 10 kV and the sample was injected at 12.3 kPa for 95 s. The detection wavelength was set at 230 nm. Under the optimum conditions, this present focusing technique improved the sensitivity enhancement by 853-fold, 893-fold, 933-fold and 925-fold for Prednisone, Hydrocortisone, Prednisolone and Betamethasone, respectively. The limit of detections were 4-8 μg/L(S/N=3). The calibration curves were linear at the concentration of 0.015 to 14.0 mg/L. The developed method was used to analyze the glucocorticoids in cosmetics. The recoveries ranged from 91.7% to 108.0%. The RSD values(n=6) were less than 4.4%. This method can be applied to determine trace glucocorticoids in different cosmetics.3. Two on-line pre-concentration techniques including dynamic pH junction and sweeping by microemulsion electrokinetic chromatography method were used to analyze two glucocorticoids(Hydrocortisone Sodium Phosphate and Prednisolone Sodium Phosphate) in cosmetics. The running buffer was composed of SDS 2.6%(w/w), octane 0.6%(w/w), 1-butanol 6.0%(w/w), 8 mmol β-cyclodextrin, 40 mmol/L phosphate buffer(pH=2.8). The conditions of sample injection was 14 kPa×90 s. Separating voltage was 12 kV. The detection wavelength was set at 247 nm. Under the optimum conditions, the sensitivity was improved 786-fold and 723-fold for Hydrocortisone Sodium Phosphate and Prednisolone Sodium Phosphate compared with convetional CE method. The limit of detections(S/N=3) were 8 μg/L and 10 μg/L for Hydrocortisone Sodium Phosphate and Prednisolone Sodium Phosphate, respectively. The calibration curves were linear at the concentration of 0.03 to 15 mg/L. The developed method was used to analyze the glucocorticoids in cosmetics. The recoveries ranged from 92.0% to 110%. The RSD values were less than 4.2%(n=6). The entire analysis process was completed in 10 min. It is obvious that the developed method could be used for the determination of glucocorticoids in cosmetics.