磺基水杨酸-铁(Ⅲ)体系光度分析法测定维生素C的研究

Study on the determination of vitamin C with sulfosalicylic acid-iron(Ⅲ) system by spectrophotometry

磺基水杨酸与Fe(Ⅲ)在pH2.00～3.00的溶液中形成紫红色磺基水杨酸合铁(Ⅲ)配离子,维生素C在酸性条件下的还原性,可将Fe(Ⅲ)定量还原为Fe(Ⅱ),使Fe(Ⅲ)-磺基水杨酸体系的颜色退去,其吸光度降低值与维生素C含量在一定范围内呈良好的线性关系,据此提出了测定维生素C含量的新方法。对影响体系吸光度的不同变量和参数进行了研究和选择。方法线性范围为2.0×10-6～1.2×10-4mol/L,检出限为1.46×10-6mol/L,回收率为97.8%～100.4%。该方法简单、灵敏度高、选择性好,用于橙汁、蔬菜中维生素C含量的测定,结果满意。

Sulfosalicylic acid and Fe（Ⅲ）could form a purple-red complex in a solution with a pH value of 2.00～3.00,and the reducing nature of vitamin C in acid medium could reduce Fe（Ⅲ）to Fe（Ⅱ）in order to reduce the absorbance of the Fe（Ⅲ）-sulfosalicylic system.The absorbance reduction of Fe（Ⅲ）-sulfosalicylic system was in a linear relationship with the contents of vitamin C in a definite range,based on which a new method for the determination of vitamin C was developed.Different variables and parameters affecting the absorbance were studied and optimized.Under the optimum experimental conditions,the linear range of determination was 2.0×10^-6～1.2×10^-4mol/L,the detection limit was 1.46×10^-6 mol/L,and the recoveries were 97.8%～100.4%.The method was simple,accurate and sensitive,and has been used for the determination of vitamin C in orange juice and vegetable samples with satisfactory results.