Highly sensitive detection of theophylline by differential pulse voltammetry using zinc oxide nanoparticles and multiwalled carbon nanotubes-modified carbon paste electrode

Theophylline is a kind of methyl xanthine derivative that can be found in various foods and is a widely used bronchodilator drug. It is significant to detect theophylline by a sensitive, low-cost, and rapid determination technique. In the investigation, zinc oxide (ZnO) nanoparticles and multiwalled carbon nanotubes (MWCNTs) co-modified carbon paste electrode (CPE) was fabricated by a simple procedure and then was successfully applied to determine theophylline. The electrochemical behavior of the modified electrode was explored using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Compared with the bare CPE and MWCNTs/CPE, the ZnO-modified MWCNTs/CPE electrode (ZnO/MWCNTs/CPE) exhibited good promoting effect on the electrochemical reaction of theophylline. Under the optimized experimental statuses, the differential pulse voltammetric peak currents can be used to detect TP, since it had a linear relationship with the theophylline concentration in the range of 3.3 × 10⁻⁷–1.3 × 10⁻⁴ M. The detection limit is 8.3 × 10⁻⁸ M (S/N = 3), and the sensitivity is 0.12048 μA μM⁻¹. Furthermore, the fabricated sensor shows high sensitivity, good selectivity, and good stability toward theophylline determination. Finally, we used the prepared electrode as an actual sample to the determination of theophylline in pharmaceutical formulations.