title: Determination of hydroquinone in cosmetic emulsion using microdialysis sampling coupled with high-performance liquid chromatography.
abstract: A method based on microdialysis sampling combined with high-performance liquid chromatography (HPLC) has been developed for the determination of hydroquinone in cosmetic emulsion. In microdialysis sampling, using deionized water as perfusate, a probe length of 10mm and dialysis flow-rate of 5 microl min(-1) were found to be the optimum conditions for the analysis. The accuracy (% bias) for intra-day (n=3) and inter-day (n=12, four consecutive days) ranged from -9.5 to 13.0% with a precision less than 7.55% relative standard deviation (R.S.D.). Recovery obtained between 89 and 112% by adding hydroquinone standards into medicated cosmetics and the coefficients of variance between 0.5 and 3.3%. The linearity of calibration curve is in the range of 2 microM-2 mM with an R(2) value for the linear regression of 0.9981. The detection limit is 0.2 microM derived from the three times of signal-to-noise ratio. This method has been applied to determine the hydroquinone content in medicated and non-medicated cosmetics. The contents of hydroquinone in the medicated cosmetics are 5.36% (0.12% R.S.D., n=3) and 3.85% (0.26% R.S.D., n=3), respectively; in contrast to the percentages given by the manufacturer are 5 and 4%, the accuracy (% bias) are 7.20 and 3.75%, respectively. No hydroquinone was detected in non-medicated cosmetics. The proposed method has the advantages of easy sample pretreatment, rapid isolation and lower organic solvent consumption than in other methods for the determination of hydroquinone in cosmetics.
authors.affiliation: Department of Biological Engineering, Yung Ta Institute of Technology, Pingtung, Taiwan.
authors.forename: Cheng-Hui
authors.initials: CH
authors.lastname: Lin
authors.forename: Jeun-Yuan
authors.initials: JY
authors.lastname: Sheu
authors.forename: Hsin-Lung
authors.initials: HL
authors.lastname: Wu
authors.forename: Yeou-Lih
authors.initials: YL
authors.lastname: Huang
mesh_terms: D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D003358:Cosmetics / Q000032:analysis* / Q000737:chemistry; D004655:Emulsions / Q000032:analysis*; D006801:Humans; D006873:Hydroquinones / Q000032:analysis*; D017551:Microdialysis / Q000379:methods; D015203:Reproducibility of Results; D013678:Technology, Pharmaceutical / Q000379:methods
chemical_list: D003358:Cosmetics; D004655:Emulsions; D006873:Hydroquinones; C031927:hydroquinone