Multi-walled Carbon Nanotubes/Ionic Liquid Nanocomposite Modified Carbon-ceramic Electrode: Electrochemistry and Measurement of Tryptophan in the Presence of Uric Acid

In the present work, an efficient modified carbon-ceramic electrode by multi-walled carbon nanotubes/ionic liquid nanocomposite (MWCNTs/IL/CCE) was prepared through a simple and repeatable procedure. The introduced modified electrode was used for the study of the electrochemical behaviour and determination of tryptophan (Trp) in the presence of uric acid (UA) using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometry techniques. The MWCNTs/IL/CCE exhibited high electrocatalytic activity toward the oxidation of Trp in phosphate buffer solution (pH 7.0) which led to produce an anodic peak at about 0.67 V vs. saturated calomel electrode. The influential parameters such as pH, amount and ratio of MWCNTs/IL in the nanocomposite modifier on the electrocatalytic activity of the MWCNTs/IL/CCE were studied and optimized. Under the optimum conditions, the anodic peak current in DPV method is linear for the Trp concentrations in the ranges of 5×10-7 M to 7×10-5 M with a correlation coefficient of 0.998 and detection limit of 3.2×10-7 M (S/N=3). The relative standard deviation of the anodic peak current obtained for a 5.0×10-5 M Trp solution was 2.2% (n=6). Finally, DPV method was applied for simultaneous determination of Trp and UA, which demonstrates the applicability of the present modified electrode.