The combined effects of pH and temperature on penicillin G decomposition and its stability modeling

The stability of penicillin G was analyzed as a function of temperature, pH , and the combined effects of pH and temperature were investigated by propo sing a second-order polynomial model for penicillin G decomposition reactio n rate constant. The modeling results obtained for the first-order decompos ition reaction of penicillin G are in good agreement with the experimental data obtained at the pH range of 1.8-10.0 and temperature range of 0-52 deg rees C. The stability analysis shows that penicillin G is more stable at th e pH range of 5.0-8.0 than out of it and lower temperatures for subsequent isolation. The maximum stability of penicillin G is at about pH 6.0 and its instability its much higher at acidic than basic pH values. The stability of penicillin G decreases by increase in temperature for all pH values. The stability results as well as the proposed second-order model for penicilli n G decomposition reaction rate constant can be used for investigating peni cillin G losses during its isolation process. (C) 1999 Elsevier Science Ltd . All rights reserved.