Sensitive and Selective Theophylline Electrochemical Detection on ZnO Nanoflowers/Graphene Oxide/Boron-Doped Diamond Nanoparticles.

Theophylline is among bronchodilator drugs consumed to overcome breathing difficulties, but accurate monitoring is required to avoid side effects. Therefore, this study aimed to develop a screen-printed electrode (SPE). Theophylline is among bronchodilator drugs consumed to overcome breathing difficulties, but accurate monitoring is required to avoid side effects. Therefore, this study aims to develop a screen-printed electrode (SPE) modified with zinc oxide nanoflowers (ZnONF) and graphene oxide (GO) nanocomposites along with boron-doped diamond nanoparticles (ZnONF/GO/BDDNPs/SPE) to detect theophylline. ZnONF is synthesized using the hydrothermal method, and the nanoflower morphology is confirmed through field emission-scanning electron microscopy with an average petal size of 62.33 nm. In electrochemical detection of theophylline, the differential pulse voltammetry (DPV) technique is used to determine the signal to background (S/B), linearity and detection limits, selectivity, reproducibility, and recovery. The results show that the S/B value produced by the ZnONF/GO/BDDNPs/SPE electrode is 4.91. The ZnONF/GO/BDDNPs/SPE electrode also exhibits the highest active surface area (0.045 cm), facilitating enhanced electron transfer. This value is higher compared to that of the ZnONF unmodified electrode. The limits of detection and quantification values are 0.17 and 0.58 μM, respectively. Theophylline measurements using the electrodes prove to be selective against similar compounds and determination in the real sample, namely, theobromine, caffeine, ascorbic acid, and uric acid. Good precision values are obtained with a %RSD value of 0.73%. The accuracy is tested in actual samples of urine, medicine, and coffee, indicating good recovery values of 103.69, 96.2, and 94.19%, respectively. In conclusion, ZnONF/GO/BDDNPs electrode is suitable for theophylline determination and health monitoring.