[Simultaneous analysis of five organic acids in aqueous, lotion, and cream cosmetics by capillary electrophoresis]

An indirect ultraviolet detection method for simultaneous analysis of five organic acids by capillary electrophoresis was established. The concentration of the tetradecyltrimethylammonium bromide (TTAB) surfactant in the background electrolyte solution and the pH of the solution were optimized. Five organic acids formic acid, malic acid, citric acid, glycolic acid, lactic acid were effectively separated from each other within 6 min with an electrolyte solution (15 mmol/L potassium hydrogen phthalate and 0.4 mmol/L TTAB, pH 5.6) under conditions of -15 kV, 25℃, and 254 nm, while the injection pressure was 5 kPa and the injection time was 5 s. The linear ranges were 15-600 mg/L, 30-800 mg/L, 20-700 mg/L, 40-500 mg/L, and 30-5000 mg/Lfor formic acid, malic acid, citric acid, glycolic acid, and lactic acid, respectively, with correlation coefficients of 0.9983-0.9998. The detection limits were between 0.1 μg/g and 2.0 μg/g. The method can be used for the detection of five organic acids in three types of cosmetics including aqueous, lotion and cream. At three spiked levels, the recoveries of organic acids were between 95.0% and 101.6%, and relative standard deviations (RSDs) were within 2.0%. The proposed method is easy, rapid, environment friendly, and sensitive with good reproducibility. It can be used for the monitoring of five organic acids in the production and storage of cosmetics including aqueous, lotion and cream.