STABILITY STUDY OF AZLOCILLIN SODIUM IN AQUEOUS-SOLUTION

The degradation process of azlocillin sodium in aqueous solution was investigated at various temperatures and constant ionic strength of 0.5 over a pH range of 3.5 to 7.9. The observed rates obtained by measuring the remaining intact penicillin were shown to observe first order kinetics and were shown to be significantly influenced by general acid and general base catalysis. The catalytic rate constants imposed by citrate and phosphate ions at 50-degrees-C were calculated. The apparent heats of activation for azlocillin sodium degradation in solution were determined to be between 13 Kcal. mol-1 and 19 Kcal. mol-1 in all cases studied. The pH-rate profile in buffer solutions showed a minimum at a pH of 4.8. At zero buffer concentration the maximum stability was shifted to a pH of 5.3. The effect of temperature has been determined and from this data the stability of azlocillin sodium at 25-degrees-C and 4-degrees-C has been predicted.