A simple selective method for determination of ascorbic acid using polymerized direct blue 71 (DB71)
is described. Anodic polymerization of the azo dye DB71 on glassy carbon (GC) electrode in 0.1M H2SO4
acidicmediumwas found to yield thin and stable polymeric films. The poly(DB71) filmswere electroactive
in wide pH range (1–13). A pair of symmetrical redox peaks at a formal redox potential, E0 =−0.02V vs.
Ag/AgCl (pH 7.0) was observed with a Nernstian slope −0.058 V, is attributed to a 1:1 proton + electron
involving polymer redox reactions at the modified electrode. Scanning electron microscope (SEM), atomic
force microscope (AFM) and electrochemical impedance spectroscopy (EIS) measurements were used for
surface studies of polymer modified electrode. Poly(DB71) modified GC electrode showed excellent electrocatalytic
activity towards ascorbic acid in neutral buffer solution. Using amperometric method, linear
range (1×10−6–2×10−3 M), dynamic range (1×10−6–0.01M) and detection limit (1×10−6 M, S/N = 3)
were estimated for measurement of ascorbic acid in pH 7.0 buffer solution. Major interferences such as
dopamine and uric acid are tested at this modified electrode and found that selective detection of ascorbic
acid can be achieved. This new method successfully applied for determination of ascorbic acid in
commercial tablets with satisfactory results.