Analysis of parabens in cosmetic products using thin layer chromatography and potentiometric titration

Abstract

Parabens are chemical preservatives used in several products, including cosmetics. These compounds increase the useful lifetime of products and prevent the development of fungi and bacteria. They can be added individually or in mixtures, increasing the activity against the action of pathogenic microorganisms. The use of parabens in cosmetic products needs to be monitored due to its lipophilic character, which in high concentrations can accumulate in the tissues of the body or induce allergic dermatites. In order to ensure consumer safety, this work aimed to analyze parabens in cosmetic samples using thin layer chromatographic and potentiometric titration. The eluent used was dichloromethane: methanol (98: 2, v/v). For sample preparation, a solid-liquid extraction has been performed. Different solventes were tested in this step: 100% etanol, etanol: water (50:50, v/v) and acidified aqueous solution (water: acetic acid 1%, v/v). Potentiometric titration was performed using digital pH meter and H2SO4 as titrant. Five samples were analyzed. According to the obtained results, two samples did not contain any preservatives, one contained only methylparaben and two contained methyl and propylparabens. It was also possible to conclude that parabens concentrations were within the recommended values by ANVISA. The method showed inter-assay precision (variation coefficient) less than 5.0% for all samples. Therefore, the developed method proved to be a simple and accessible tool which uses small volume of organic solvent and can be applied in quality control of methyl and propyl-parabens in cosmetic products.