Mathematical Representation of the Stability of Ibuprofen in Binary and Ternary Solvent Mixtures at Various Temperatures

The stability of ibuprofen in the binary and ternary solvents of polyethylene glycol 200, ethanol and water was measured at four different temperatures (298.15, 308.15, 318.15 and 328.2 K). A modified high performance liquid chromatography method was used for determining the residual concentrations of ibuprofen in the solvent mixtures. The mobile phase was composed of acetonitrile and water (adjusted to pH 1.81 with orthophosphoric acid) with the ratio of 60:40; it was passed through the column at the flow rate of 1 mL·min−1 for conditioning the system (25 min) and carbamazepine was used as the internal standard. The Jouyban–Acree model was used to fit the stability factors of ibuprofen at several temperatures and in different solvent mixtures and the obtained mean relative deviation value for 204 stability data points is 19.0 %.