Theophylline electrochemical sensing in pharmaceutical drugs using disposable boron-doped diamond thin film electrodes

The main idea of this work was to investigate the voltammetric behavior of theophylline using cyclic voltammetry (CV), and to compare differential pulse voltammetry (DPV) and square wave voltammetry (SWV) for application in the development of a method for this analyte. The electrochemical results indicate that the homely printed sensor with a boron doped diamond electrode can significantly improve the electrocatalytic activity towards the oxidation of theophylline in 0.5 M sulfuric acid. After parameter optimization and comparison of the DPV and SWV methods, it was shown that both methods can effectively detect theophylline in the same concentration range from 3.8 to 27 µM. Slightly better analytical parameters in terms of detection limit and quantification limit were obtained by the SWV method and were 0.24 µM and 0.73 µM, respectively. In the case of DPV, the detection limit was 0.39 µM, while the quantification limit was at a value of 1.17 µM. The practical applicability was demonstrated through the development of the SWV method for the detection of theophylline in pharmaceutical formulations. The tests were performed in triplicate and using the standard addition method. Excellent agreement with the declared values showed that the proposed sensor can be a satisfactory alternative for fast, precise and accurate monitoring of theophylline concentration in real samples, with great potential for further modification and technology transfer for miniaturization and disposable sensing.