Desenvolvimento de metodologias analíticas para determinação de hidroquinona em cosméticos e medicamentos

Abstract

The excessive pigmentation of skin is due to abundant production of melanin by melanocytes located in the skin epidermal layers. Several cosmetic and pharmaceutical formulations had been industrialized as well as compounded in pharmacy such as gel and creams containing hydroquinone as a unique active ingredient. The quantitative determination of hydroquinones present in these formulations necessitates validated analytical methods that are reliable, economical and ecologically favorable. The objectives of this research were characterization of hydroquinone raw material to assure its use in pharmaceutical and cosmetic preparations as well as its quantitative determination in gel and cream formulations. A first derivative UV spectrophotometric and a high-performance liquid-chromatographic method are proposed. The UV first derivative spectrophotometric method was validated using H2SO4 0.1 N as solvent and absorptions were taken at 302.0 nm. The linearity data showed a correlation coefficient of 0.9999. The mean hydroquinone content of gels and creams were 101.7 and 97.6% with mean relative standard deviations of 0.839 and 0.878% respectively. The chromatographic method was validated using LiChrospher, 100 RP-18 (5 μm) column, mobile phase composed of water:methanol (80:20 v/v), at a flow rate of 1.0 mL/min and UV detection at 289 nm. The linearity correlation coefficient was 0.9999. The mean hydroquinone content of gels and creams were 102.2 and 98.4% with mean relative standard deviations of 0.882 and 1.252% respectively. The precisions and hydroquinone content data were statistically analyzed (F and t tests), no significant difference was observed between results obtained by proposed methods at 95% confidence level.