Determination of Ascorbic Acid Content in Pharmaceutical Samples by Spectrophotometric Method

A simple and sensitive spectrophotometric method to determine ascorbic acid content was developed through using potassium ferricyanide-Fe(Ⅲ).Ascorbic acid can reduce Fe(Ⅲ) to Fe(Ⅱ) in the buffer solution with pH of 4.2,then Fe(Ⅱ) can react with potassium ferricyanide to form blue composite.The maximum absorption wavelength of the composite is 698 nm,and when ascorbic acid is in the range of 0.21～18.00 mg/L,a good linear relationship is obtained.The linear regression equation is A=0.293 8ρ-0.010 8(mg/L) with linear correlation coefficient of 0.999 0.The detection limit and R.S.D.are 0.057 mg/L and 0.3%,respectively.The apparent molar absorption coefficient of indirect determination of ascorbic acid is 5.17×104 L·mol-1·cm-1.This method has been applied in determination of ascorbic acid in pharmaceutical samples,with average recovery of 97.8%～102.4%.