Degradation Kinetics of Cefuroxime Lysine in Aqueous Solution by LC-MS

The degradation kinetics of cefuroxime lysine in aqueous solution were investigated by a developed liquid chromatograph/mass spectrometry (LC/MS) method with pH ranging from 1.5 to 11.0. The influences of pH, temperature, ionic strength, irradiation and oxidation on the degradation rate were evaluated, and the corresponding kinetic parameters were calculated. The decomposition of cefuroxime lysine was observed to follow first order kinetics under all the experimental conditions, and the rate constant increased with an increase in the temperature, ionic strength and oxidation concentrations. The maximum stability was observed in the pH region from 3.6 to 9.0. The irradiation showed obvious effect on the stability. The activation energy was determined to be 116.0 kJ/mol, with the half-life (t(1/2)) and shelf-life (t(0.9)) to be 211.3 and 32.13 h at 25 degrees C, respectively. An empirical relationship between the rate constant (k) and the pH was depicted as: k=0.0241 + 2.024*10(-5)*exp[1.326(pH)].