Adsorptive Cathodic Stripping Voltammetric Determination of Theophylline at Hanging Mercury Drop Electrode

Adsorptive stripping voltammetry was used for the determination of trace amounts of theophylline. Theophylline in pH 7.5 Britton-Robinson buffer gives an adsorptive stripping voltammetric peak at a hanging mercury drop electrode at –0.38 V at accumulation potential 0.0 V versus Ag—AgCl. The optimum conditions of pH, accumulation potential and accumulation time were studied using differential-pulse voltammetry. The calibration graph for the determination of theophylline was linear in the range 0.6–3.6 µg l–1 with a relative standard deviation of 2%. The detection limit was 0.6 µg l–1 after 180 s accumulation at 0.0 V. The effect of some purine compounds and metal ions on the peak height of theophylline was studied. The presence of CuII ions enhanced the theophylline peak and the behaviour of the theophylline–copper complex was investigated. The method was applied to the determination of the drug in commercially available dosage forms. A comparison of the proposed method with previously reported methods was also made.