ABSTRACT
A kinetic and thermodynamic study of the aerial oxidation of perphenazine is presented. The investigations involve factors that are likely to be operative under normal conditions of the storage of the drug in liquid formulations. The factors which have been investigated one at a time comprise, pH, dissolved oxygen, metal ions, solvent, ionic strength and temperature. The experimental results were discussed and the kinetic parameters evaluated at 60°C and 80°C were employed for the computation of the activation energy E. [a] [#], enthalpy change [
Subject(s)
Kinetics , Thermodynamics , Oxidation-Reduction , Hydrogen-Ion Concentration , Oxygen , Solvents , Temperature , Drug StabilityABSTRACT
The oxidation of perphenazine to perphenazine sulphoxide by peroxyacetic acid was kinetically studied utilizing first derivative UV-spectrophotometry and a simple iodometric procedure. The first-derivative UV-spectrophotometric procedure indicates that the reaction with respect to perphenazine is most probably zero-orer at the initial stage with a rate constant [k0] of magnitude 5.62x10-8 mol L-1S-1. Based on the titrimetric procedure in which 0.01 N Na2S2O3 was employed the reaction with respect to peroxyacetic acid is most probably second order initially having a rate constant [k2] equal to 0.05805 L mol-1 S-1. the disparity between the orders with respect to concentration [i.e.nc] and time [i.e.n1] for peroxyacetic acid was highlighted