Hydroquinone has been used for decades as a skin lightening agent. Its use in cosmetics has been banned as a result of skin problems including contact dermatitis and ochronosis. A total of 22 samples of different skin whitening cosmetics were collected from local market. They were analyzed by using thin layer chromatography and HPLC for qualitative and quantitative determination of their hydroquinone contents. The hydroquinone was extracted from samples by using 96% ethanol and was subjected to TLC analysis. Eleven out of 22 samples were found to contain hydroquinone. The HPLC analysis showed the concentration of hydroquinone ranged from 0.002% to 0.092% in the cosmetic samples.
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机译:Estimativa de estro em vacas leiteiras utilizando quantitative metodos preditivos Dairy cows estrus estimation using predictive and quantitative methods