Online Determination of Glucocorticoids in Cosmetics by Large Volume Sample Injection-Reduced Electric Field Sweeping and Microemulsion Electrokinetic Chromatography

KeyWord:microemulsion electrokinetic chromatography  online pre-concentration  large volume sample injection  sweeping  cosmetic  glucocorticoid

Abstract:

      A simple and efficient online sample pre-concentration method composed of large volume sample injection(LVSI)-reduced electric field sweeping(REFS) and microemulsion electrokinetic chromatography(MEEKC) was developed for the determination of glucocorticoids(prednisone,hydrocortisone,prednisolone and betamethasone) in cosmetics.The microemulsion background buffer was composed of 2.4%dodecyl sodium sulfate,6.6% butanol,0.6%octane and 30 mmol/L borate buffer(pH 8.2).The separation voltage was 9.6 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£¬the enrichment factors ranged from 853 to 933.The calibration curves were linear in the concentration of 0.015-14 mg/L.The limits of detection(S/N=3) were in the range of 4-8 ¦Ìg/L.The developed method was used to analyze corticosteroids in cosmetics with recoveries of 93.7%-103.8%and RSDs(n=5) not more than 4.4%.