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 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.
Zajac
Marianna
M
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Poznań University of Medical Sciences, Grunwaldzka 6, 60-780 Poznań, Poland. mzajac@amp.edu.pl
Cielecka-Piontek
Judyta
J
Jelińska
Anna
A
D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002021:Buffers; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004355:Drug Stability; D000077727:Ertapenem; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D006878:Hydroxides / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry; D047090:beta-Lactams / Q000737:chemistry*
D000900:Anti-Bacterial Agents; D002021:Buffers; D006878:Hydroxides; D012996:Solutions; D047090:beta-Lactams; D014867:Water; C031356:hydroxide ion; D000077727:Ertapenem