磷钼钨三元杂多酸光度法测定药物中的抗坏血酸

研究了抗坏血酸与磷钼钨三元杂多酸的显色反应，提出了借磷钼钨杂多蓝测定抗坏血酸的分光光度法。最大吸收波长为７３０ｎｍ，抗坏血酸在０．０８～１０ｍｇ／Ｌ范围内线性良好。回归方程为Ａ＝１．０５×１０４Ｃ＋０．０１７，线性相关系数γ＝０．９９９５，表观摩尔吸光系数ξ７３０＝１．０５×１０４Ｌ·ｍｏｌ－１·ｃｍ－１，方法检出限为０．０４ｍｇ／Ｌ，回收率为９４～１０２％，相对标准偏差≤１．５％（ｎ＝８）。本方法由于钨钼的混合配位增强了氧化能力，较之二元杂多酸的方法，省去了水浴加热等操作，只需在室温下反应３０ｍｉｎ，吸光值至少可稳定６ｈ。过量的黄色杂多酸可加入适量的氢氧化钠溶液分解，从而获得色泽纯正的高灵敏度显色体系。

Spectrophotometric Determination of Ascorbic Acid in Pharmaceutical Preparations with Tungstomolybdophosphoric Acid

A simple and sensitive spectrophotometric method is established for the determination of ascorbic acid based on the reaction of ascorbic acid with tungstomolybdophosphorus heterpoly compound.The maximum absorption is at 730nm. Beer's law is followed in the range of 0.08-10 mg L^-1 ascorbic acid. The apparent molar absorptivity is 1.05×10⁴ L·mol^-1·cm^-1,and the linear regression equation is A=1.05×10⁴C+0.017 with a linear correlation coefficient of 0.9995. The detdrion limit of 0.04mg·L^-1,the recovery of 94%-102% and the relative standard deviation of less than 1.5% (n=8) were estimated, respectively. Instead of heating,the color reaction can be completed by standing at room temperature for 30 minutes. The absorption of excess tungstomolybdophosphorus heteropoly yellow can be removed by the addihon of a certain amount of sodium hydroxide solution, thus the sensitivity and selectivity of the method are improved.The proposed method has been applied to the determination of ascorbic acid content in vitamin C tablets.