Stability of ertapenem in aqueous solutions |
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Authors: | Zajac Marianna Cielecka-Piontek Judyta Jelińska Anna |
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Institution: | Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Poznań University of Medical Sciences, Grunwaldzka 6, 60-780 Poznań, Poland. mzajac@amp.edu.pl |
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Abstract: | 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 microm, 250 mm x 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. |
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Keywords: | Ertapenem Stability in aqueous solutions pH-rate profile Catalytic rate constants Thermodynamic parameters |
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