Procedure:

● To prepare KCl solution having a concentration of 3mol/L, weigh 22.365 g KCl.
● Transfer the salt into a 100ml volumetric flask and makeup with double distilled water.
● To prepare supporting electrolyte solution, pipette out 6.67ml KCl solution (3mol/L) into a 200mL volumetric flask and makeup with double distilled water.
● Weigh 0.88 g ascorbic acid to prepare Vitamin C standard solution.
● Transfer weighed ascorbic acid into a 50mL volumetric flask.
● Dissolve and make up to the mark with double distilled water.
● Prepare the measuring solution by pipetting 11ml supporting electrolyte and 0.10ml vitamin C standard solution (0.1 mol/L) into the electrochemical cell.
● The bare GC and modified GC (Bi2O3) are used as a working electrode, the saturated calomel electrode as a reference electrode, and the platinum wire electrode as an auxiliary electrode.
● Screen printed electrode (SPE) is also used that consists of three electrodes: the working electrode (WE), the reference electrode (RE), and the counter or auxiliary electrode (CE/AE).
● The CV graph represents the current at the working electrode versus the applied voltage plot and important peak parameters.