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

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.