Quantification of theophylline in anti-asthmatic drugs via graphene-ZnO based sensors

This study presents a novel electrochemical sensor for theophylline quantification based on a graphene-ZnO nanocomposite. To create the sensor, the glassy carbon electrode was altered by incorporating a carefully balanced mixture of 30 % graphene and 70 % ZnO. Characterization techniques, including SEM, XRD, and FTIR, confirmed the successful synthesis and integration of the nanocomposite. The sensor showed outstanding analytical capabilities, with two distinct linear ranges from 0.1 to to 100 μM, and a detection limit of 0.03 μM. Through cyclic voltammetry experiments, it was determined that the oxidation process was diffusion-controlled, and the best response was achieved at pH 7.0. The sensor showed strong selectivity towards typical interferents, with the ability to withstand concentrations of up to 500 μM for certain substances. Practical applicability was validated through analysis of pharmaceutical formulations and spiked biological samples, yielding recoveries of 98.5–101.2 % and 96.8–103.1 %, respectively. The sensor showed good reproducibility (RSD < 4 %) and retained 95.6 %, indicating promising potential for routine theophylline monitoring in clinical and pharmaceutical settings.