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 μm, 250 mm × 4 mm; mobile phase: methanol–phosphate buffer 25 mmol l−1, pH 6.5 (15:85, v/v); flow rate—1.2 ml/min; detection UV—298 nm) and UV (294 nm). 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.