Voltammetric study of polyviologen and the application of polyviologen-modified glassy carbon electrode in amperometric detection of vitamin C

The voltammetric behavior of viologen oligomers prepared from butylviologen dibromide and the factors influencing polyviologen film formation were investigated at a glassy carbon electrode (GCE). Based on the voltammetric observations, phosphoric acid is crucial to the formation of a stable polyviologen film on a GCE. The polyviologen-modified glassy carbon electrode (PVGCE) was employed to determine vitamin C (i.e., ascorbic acid) in order to demonstrate the electroanalytical application of the electropolymerized polyviologen film. The PVGCE was found capable of accumulating vitamin C at electrode surface in a slightly basic solution (pH = 7.8) and induce a negative shift of oxidation potential of vitamin C. Vitamin C was detected by hydrodynamic amperometry at +0.1 V (vs. Ag/AgCl) in a batch-injection cell; no accumulation time is required. The dependence of oxidation current on concentration was linear from 5.00 x 10(-7) M to 1.22 x 10(-4) M with a regression coefficient of 0.9993. Several real samples were analyzed and the results exhibit good agreement with those determined by iodimetric titration.