Fe(Ⅲ) Replacement Redox Titration of L-Ascorbic Acid in Vitamin C Tablets and Injections

It was proposed that the ascorbic acid in vitamin C (VC) tablets or injections was determined in the following steps: ① a definite amount of ferric ammonium sulfate (primary standard) was dissolved in dil. HOAc solution,and an excess amount of KI was added,and the solution was kept in derk for 10 min for quantitative liberation of iodine (as I-3);② a definite amount of the sample of VC tablet or injection was dissolved in 200 mL of 0.1 mol·L-1 HOAc solution,which was used as titrant to react with the iodine (as I-3) liberated in the former step. Consistents results were obtained by this method and the pharmacopoeia method.