Thermal behaviour of erythromycin-active substance and tablets: Part 1. Kinetic study of the active substance under non-isothermal conditions

The application of thermal methods is of great importance in the solution of pharmaceutical problems, such as the control of raw materials, the determination of purity, the qualitative and quantitative analysis of drug formulation, tests of thermal stability and compatibility, the determination of kinetic parameters etc. The evaluation of thermal stability in the solid state is mostly made by analyzing their decomposition under isothermal and non-isothermal conditions. This study reports the study on the thermal behaviour of erythromycin-active substance and tablets, respectively, the determination of the kinetic parameters for the decomposition process under non-isothermal conditions. For the determination of kinetic parameters from the TG/DTG curves, were utilized the following methods: Friedman isoconversional, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, Li–Tang, and Kissinger, respectively, a dynamic nitrogen atmosphere and different heating rates: 2.5, 5, 7.5, 10, and 15 °C min −1 . Thermoanalytical curves showed that the active substance is thermally more stable than the tablets and the values of activation energy indicate a considerable thermal stability of active substance. The decrease in stability was attributed to the presence of excipients.