Stability of ertapenem in aqueous solutions

The kinetics of degradation of ertapenem was studied in aqueous solutions at 303, 313, 323 and 333 K and pH 0.42-12.5. Degradation was studied using two methods: HPLC (LiChrospher RP-18 column, 5 mu m, 250 mm x 4 mm; mobile phase: methanol-phosphate buffer 25 mmol l(-1), pH 6.5 (15:85, w/v); flow rate-1.2ml/min; detection UV-298nm) and UV (294nm). Specific acid-base catalysis involves: (a) hydrolysis of ertapenem. catalysed by hydrogen ions; (b) hydrolysis of ertapenem dianions catalysed by hydroxide ions; (c) spontaneous hydrolysis of zwitter ions and dianions of ertapenem under the influence of water. The thermodynamic parameters of these reactions-energy, enthalpy and entropy of activation were calculated. It was observed that buffer catalysis occurred in acetate, phosphate and borate buffers. (c) 2006 Elsevier B.V. All rights reserved.