Thermal behavior of cetylpyridinium hydrochloride and its association with sugar alcohols and flavoring agents: a preformulation study

Cetylpyridinium chloride (CPC) is a chemical compound used widely in industry, having been adopted in pharmaceutical and cosmetic formulations as a preservative, antimicrobial, and antiseptic agent. In pharmaceutical development, thermal analysis and Infrared Spectrum (FTIR) are widely used on preformulation studies. Thus, in this work we performed the thermal characterization of CPC through DSC and TG/DTA techniques, and evaluated it by FTIR to understand the thermal events that characterize CPC. In addition, its binary combinations with possible adjuvants: sugar alcohols (sorbitol and xylitol) and flavoring agents (menthol and thymol), were evaluated. Statistical analysis using Pearson's correlation allowed us to define clearly the extent of these interactions. The DSC study showed endothermic peaks at 84.09 °C and 233.84 °C for CPC. TG analysis indicated mass loss of 92.91% at a temperature of 239.57 °C. DTA evaluation showed endothermic peaks at 83.68 °C and 240.12 °C. In the FTIR analysis, bands of characteristic spectra for CPC were presented. The evaluation of binary combinations with the components studied allowed for the identification of interactions of CPC with menthol and thymol, with alterations of melting point and eutectic mixtures formation, even at room temperature, with thymol. The spectral constancy of CPC and mixtures with different components were evaluated through linear correlation, with no significant chemical interactions evidenced. This was due to the Pearson's correlation values being greater than 0.8, which represents an absence of chemical interactions between the components tested.