AD钙盐中的维生素A是以其乙酸酯的形态加入,而后者不溶于水.根据此性质,将AD钙盐试样用水浸取即可使维生素A与基体组分离,将不溶物分出,溶于乙醇中并定容为10 mL,随即可在此试样乙醇溶液中用UV-分光光度法测定维生素A.在维生素A的吸收峰325 nm波长处,用1 cm石英吸收皿以乙醇作参比液测得其吸光度.用高纯度的维生素A乙醇酯(纯度99.9%)作标准制作标准曲线,得其线性回归方程为cVC=16.899 A+0.059,r=0.999 6,方法的回收率在97.7%至100.1%之间.此方法远较国家标准方法和药典方法简单、可行.

Vitamin A is added in the AD calcium salt in the form of ethyl ester,which is insoluble in water.Based on this fact,vitamin A was separated from the matrix by extraction with water.The insoluble substance was collected and dissolved in ethanol and diluted to 10 mL quantitatively.Vitamin A in the sample solution was then determined by UV-spectrophotometry.Its absorbance was measured at its absorption maxima of 325 nm,with 1 cm quartz absorption cell using ethanol as reference solution.High purity (99.9%) ethyl ester of vitamin A was used as standard in the preparation of standard curve,the linearity of which was given by the regression equation cVA=16.899 A+0.059 (r=0.999 6).Results of recovery test obtained were in the range from 97.7% to 100.1%.This method was proved to be much simpler than the method given in GB standard and in pharmacopoeia.