Kinetic and thermodynamic analysis of degradation of doripenem in the solid state

Abstract

The kinetic and thermodynamic parameters of degradation of doripenem were studied using a high-performance liquid chromatography method. In dry air, the degradation of doripenem was a first-order reaction depending on the substrate concentration. At increased relative air humidity, doripenem was degraded according to the autocatalysis kinetic model. The dependence ln k = f1/T) was described by the equations ln k = 5.10 ± 13.06 − (7576 ± 4939)(1/T) in dry air and ln k = 46.70 ± 22.44 − (19,959 ± 8031)(1/T) at 76.4% relative humidity (RH). The thermodynamic parameters Ea, ΔH≠a, and ΔS≠a of the degradation of doripenem were calculated. The dependence ln k = f (RH%) was described by the equation ln k = (0.155 ± 0.077) × 10−1 (RH%) − (3.45 ± 21.8) × 10−10. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 722–728, 2012