Prediction of Chemical Stability of Ibuprofen in Solution: An Accelerated Aging Study

Abstract

Ibuprofen, propionic acid derivative, was subjected to different temperature (20, 30, 37, 40, 50 and 60 ºC) and pH (3, 4, 5, 6, 7 and 8) conditions. The samples were assayed at time intervals 0, 12, 24, 36 and 48 h by taking their UV/VIS absorbance at wavelengths 272 and 258 nm. Ratios of absorbance at any time were taken as a parameter, proportional to the concentration of intact substance. The degradation processes were assumed to follow pseudo-first-order kinetics and rate constants (K) were calculated by plotting logarithm of absorbance ratio versus time and slope of the regression lines were considered to be equivalent (K/2.303). The energy of activation (E_a) at particular pH, was calculated by Arrhenius equation i.e., K = Ae^-Ea/RT. Ibuprofen is found to be moderately resistant to the acid treatment. Respective E_a values at pH 3, 4, 5, 6, 7 and 8 were calculated to be 19.17, 20.60, 21.81, 24.22, 22.45 and 21.16 Kcal/mol. The compound under study exhibited thermolability and is recommended to be maintained at 20 ºC.