Simultaneous Determination of Ascorbic Acid, Uric Acid and Tryptophan by Novel Carbon Nanotube Paste Electrode

In the present paper, electrochemical methods were used to investigate the behavior of ascorbic acid at a carbon paste electrode modified with 2,2'-((1E)-(1,2 phenylenebis(azanylylidene)) bis(methanylylidene))bis(benzene-1,4-diol) (PBD) and oxidized multiwall carbon nanotubes. The modified carbon paste electrode showed high electrocatalytic activity toward ascorbic acid; the current was enhanced significantly relative to the situation prevailing when an unmodified carbon paste electrode was used. Cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. Using differential pulse voltammetry, the calibration curves for AA were obtained over the range of 1.0–80.0 and 80–4000.0 μM, respectively. The detection limit was 0.3 μM. The present method provides a simple method for selective detection of ascorbic acid. DPV also was used for simultaneous determination of AA, uric acid, and tryptophan at the modified electrode.  Finally, the proposed electrochemical sensor was used for determinations of these substances in in biological systems and pharmaceutical samples.