[Kinetic study on the degradation of penicillin potassium at different temperature and relative humidity]

To perform a kinetic analysis and formulation of the degradation of penicillin potassium in the solid phase at different temperature and relative humidity.

Penicillin potassium was incubated in a temperature-and-humidity-controlled oven at different temperature and relative humidity, and was determined by HPLC at suitable time intervals during the incubation.

The reaction rate was expressed as -dc/dt=k(c0-c+B), where c is the residual concentration, k degradation rate constant, c0 original concentration and B a constant related to original concentration of degradant. Degradation curves were fitted with c=c0-Bexp (kt)+B. The k was expressed as k=Aexp(-Ea/RT)exp(mHr), where active energy E. is 77.26 kJ/mol and constant m 0.1159.

The degradation of penicillin potassium could be expressed with c=c0-Bexp [Aexp (-Ea/RT)exp (mHr)t]+B.