Thermokinetic analysis of the stability of malic and salicylic acids in cosmeceutical formulations containing metal oxides

Abstract

Cosmeceutical products that contain malic acid (MA), salicylic acid (SA), and hyaluronic acid as well as a variety of antioxidants are used worldwide. Therefore, safer ingredients of cosmeceutical products have become an important issue based on sales volume. In general, the chemical composition may affect the thermal stability of a cosmeceutical product. Temperature changes may occur in the manufacturing, storage, and transport of the product, affecting its stability. Because cosmeceutical products are placed directly on the skin, sensitivity has become an increasing concern. However, potential risks have not been clearly identified. To investigate the thermal stability behavior of regular cosmeceutical materials, thermogravimetry and differential scanning calorimetry have been used. For this study, the thermal stability of MA and SA was studied, and the acids were individually mixed with CuO or Fe2O3 to evaluate the effect of adding metal oxides. According to the DSC curves, the apparent exothermic onset temperature occurred when MA and SA were mixed with Fe2O3. Apparent activation energy values of individual samples calculated using the ASTM E698 and Ozawa–Flynn–Wall methods ranged from 72.2 to 87.4 kJ mol−1 and from 84.2 to 98.7 kJ mol−1, respectively. The results can be used to calculate the optimal parameters for safe cosmeceutical manufacturing and establishing a database of MA and SA for loss prevention protocols.