2.5. Thermodynamic Stability Study

First, the selected formulations were subjected to centrifugation at 5000 rpm for 30 min. Then, the passed formulations were subjected to six heating (40 °C) and cooling (4 °C) cycles for at least 48 h at each temperature. Finally, those stable formulations were exposed to three freeze-thaw cycles at −21 °C and 25 °C for 48 h at each temperature [30]. Only passed microemulsion formulations were chosen for further evaluation.