作者:Dan Wang、Robert E. Notari
DOI:10.1002/jps.2600830427
日期:1994.4
Cefuroxime hydrolysis rate constants (k) were determined to predict the degradation rate of cefuroxime in aqueous solution as a function of pH, temperature, and buffer. At constant temperature, the pH-rate expression was: k = kH(aH+) + kS1f1 + kS2f2 + kOH(aOH-), where f1 is the fraction of cefuroxime in the undissociated form and f2 is the anionic fraction, kH and kOH are the catalytic rate constants
确定头孢呋辛水解速率常数(k)以预测水溶液中头孢呋辛的降解速率与pH,温度和缓冲液的关系。在恒温下,pH值的表达式为:k = kH(aH +)+ kS1f1 + kS2f2 + kOH(aOH-),其中f1是头孢呋辛在未解离形式中的分数,f2是阴离子分数,kH和kOH为氢活度(aH +)和氢氧离子活度(aOH-)的催化速率常数,kS1和kS2是自发水解的一级速率常数。甲酸盐,乙酸盐,磷酸盐和硼酸盐缓冲液不会催化降解。描述了kH,kS1,kS2和kOH的温度相关性,其中A(指数前项)和E(活化能)的值由k = Ae-E / RT(其中R为1.987 cal / mol-deg和T是绝对温度)。结合pH和温度方程可以预测在任何pH和温度下水溶液中头孢呋辛的水解速率。通过预测每种实验条件以及在30摄氏度下储存的重构商业产品的观察到的速率常数来验证结果。在pH无关的区域(pH范围为4至7)中观察到