Voltammetric behavior of theophylline and its determination at multi-wall carbon nanotube paste electrode

The voltammetric behavior of theophylline was investigated using cyclic and differential-pulse voltammetric techniques. The cyclic voltammetric results indicate that multi-wall carbon nanotube paste electrode can remarkably enhance electrocatalytic activity toward the oxidation of theophylline in pH 3.0 phosphate buffer solution than the carbon paste electrode. The oxidation of theophylline was observed to be a two-electron process, irreversible with diffusion character. Effects of anodic peak potential (Ep), anodic peak current (Ip) and heterogeneous rate constant (ko) have been discussed. Under optimal conditions, the anodic peak current was proportional to theophylline concentration in the range of 2.0 × 10−6 to 1.5 × 10−4 M with a detection limit of 1.97 × 10−8 M using differential pulse voltammetry. The proposed method was employed to determine theophylline in pharmaceutical formulations and urine as a real sample.