经典恒温法预测维生素C溶液的有效期

Prediction of shelf-life of Ascorbic acid solution by Classical isothermal method

目的探讨氧气溶解度的变化对经典恒温法预测维生素C溶液有效期的影响。方法以5%维生素C溶液为模型药物,分别测定其在35、40、45、50℃时的表观降解速率常数kA,根据kTcO2,d=kA计算各温度下的降解速率常数kT。分别以kA和kT的对数对温度的倒数进行拟合,并外推维生素C溶液在25℃时的表观降解速率常数kA,25℃。结果由kA和kT求得维生素C溶液的kA,25℃分别为0.5277、0.5272 mmol·L-1·h-1。结论氧气溶解度的变化对经典恒温法预测维生素C溶液的有效期无影响。

OBJECTIVE To investigate the effect of the concentration of dissolved oxygen on prediction of shelf- life of oxygen-sensitive drug by classical isothermal method. METHODS 5% Ascorbic acid solution was used as model drug and the apparent rate constants（ kA） under 35 ℃,40 ℃,45 ℃ and 50 ℃ conditions were measured,respectively. The rate constants（ kT） under the same conditions were calculated according to kTcO2,d= kA. RESULTS Two straight lines were obtained by plotting lnkAand ln kTagainst1 / T,respectively. And the calculated values of apparent rate constant at 25 ℃,kA,25 ℃,were 5. 277 × 10^- 4mol·L6- 1·h^-1 1and5. 272 × 10- 4mol·L^- 1·h^- 1,respectively. CONCLUSION The result shows that the concentration of dissolved oxygen has no effect on the prediction of shelf- life of Ascorbic acid solution by classical isothermal method.