Electrochemical Characterization and Determination of Theophylline at a Graphite Pencil Electrode using Cetyltrimethyl Ammonium Bromide as an Enhancing Agent

The oxidation of theophylline (TP) was studied at a graphite pencil electrode (GPE) in the presence of cetyltrimethyl ammonium bromide (CTAB) by cyclic and differential pulse voltammetry. The results indicated that the electrochemical responses of theophylline are apparently improved by cetyltrimethyl ammonium bromide, due to the enhanced accumulation of theophylline at pencil graphite electrode surface. Key experimental parameters such as pH of supporting electrolyte, scan rate, concentration and interferents were investigated. Under optimal conditions, the peak current was proportional to theophylline concentration in the range of 1.0×10−7 to 1.3×10−6 M with a detection limit of 2.63×10−9 M by differential pulse voltammetry. The proposed method was successfully applied to the determination of theophylline in tablet and urine samples.