Analysis of Ascorbic Acid in Supplement Tablets from the Mole Ratios of the Electrolytic Products

A unique undergraduate experiment for the quantitative analysis of ascorbic acid in dietary supplement tablets is presented. The experiment combines titration concept with electrolysis and the gas laws. Powdered supplement tablet sample is placed in the anode compartment of the electrolysis cell containing potassium iodide. Electrolytically generated I2(aq) oxidized the ascorbic acid in the sample. Starch is used as a visual indicator. The volume of H2(g) produced at the cathode is monitored and the amount of I2(aq) produced at the anode is determined from the volume of H2(g) produced at the cathode. The amount of ascorbic acid present in the sample is determined from the mole relationships between I2(aq) and H2(g). The experimentally determined amount of ascorbic acid from the electrolytic titration method agrees with the volumetric titration results and the manufacturer’s label. Preparation of an electrolysis cell, experimental procedure, and results of the electrolytic titration are presented.