重铬酸钾分光光度法测定维生素 C 的含量

建立了以 K2Cr2O7测定维生素 C 的分光光度法.在硫酸溶液中,加入过量 K2Cr2O7标准溶液氧化维生素 C,铬(Ⅵ)可被维生素 C 还原至铬(Ⅲ),其最大吸收波长为570 nm.维生素 C 浓度在0.20~16.00 mg/L 范围内与溶液吸光度呈良好线性关系,线性回归方程为 A=0.1161c+0.0013( mg/L),相关系数 r=0.9983,检出限为0.075 mg/L,相对标准偏差(RSD)为0.69%,表观摩尔吸光系数ε=2.04×104 L/(mol?cm).方法用于测定果维康 Vc 含片及柠檬汁饮料中抗坏血酸的含量,回收率在97.25%~103.75%.

Determination of Ascorbic Acid by Spectrophotometry With Potassium Dichromate

A spectrophotometric method was established to determine ascorbic acid by using potassium dichromate.In sulfuric acid solution,ascorbic acid was oxidized by excessive potassium dichromate,Cr(Ⅵ) was reduced to Cr(Ⅲ) by ascorbic acid,the maximum absorption wavelength was 570 nm,the good linear relationship was obtained in the range of 0.20～16.00 mg/L ascorbic acid.The linear regression equation was A=0.1161c+0.0013(mg/L) with correlation coefficient of 0.998 3 and the apparent molar absorption coefficient of 2.04×104 L/(mol.cm).The detection limit was 0.075 mg/L,while R.S.D was 0.69%.This method has been applied in determination of ascorbic acid in pharmaceutical samples and lemon drink,with average recovery of 97.25%～103.75%.