The Use of Malaprade Reaction and Amplification Reactions for Titrimetric Determination of Vitamin C in Tablets


Selective and sensitive titrimetric method has been developed for the determination of ascorbic acid via Malaprade reaction and Leipert reaction. Ascorbic acid was oxidized by periodate (Malaprade reaction), excess periodate was masked by molybdate at pH 3, then the produced iodate reacted with iodide in acidic medium to produce iodine, which was titrated with standard sodium thiosulphate solution using starch as indicator (amplification reaction). 50-500 µg of ascorbic acid (12 fold amplification ) was determined in aqueous solution, recovery was between 97.45% and 102.67%, and RSD was less than 4%.The method has been applied successfully to the analysis of pharmaceutical tablets. The results obtained were in agreement with the certified values and also with the British pharmacopoeia method.