Reversible potentiodynamic deposition of VO2/V2O5 network onto strongly oxidative glassy carbon electrode for quantification of tamoxifen drug

The present work demonstrates the electrochemical deposition of vanadium oxide (VO_x) onto a pretreated glassy carbon electrode. The structure of the resulting (VO_x-GCE) deposit can be considered as a mixture of (VO₂) and (V₂O₅) species confirmed by means of X-ray Photoelectrons Spectroscopy (XPS). The oxidative chemical and electrochemical treatment of the GCE is the key step for surface enrichment with negatively oxygen-containing functional groups prior to doping of VO_x species. Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) methods confirm the successful fabrication of the sensor as well. X-ray diffraction (XRD) was also used to identify the solid structure of the surface deposited film and its crystallinity. The synergistic effect of surface vanadium species promotes the catalytic activity of the developed sensor for the detection of tamoxifen (TMX) in pharmaceutical samples. The sensor exhibited a good sensitivity, high precision, stability and robustness. The optimum detection limit (DL_3σ) of TMX was 389 nM (144 ppb) calculated for a wide dynamic [TMX] range. The analytical performance of the sensor was successfully applied for real drug sample with acceptable analytical recovery percentage. The method of fabrication is simple and demonstrates an effective tailoring process of active surface materials prior to fast electron transfer kinetics. A further study focus on determining the diffusion coefficient of TMX important to design a controlled drug delivery system was conducted. The estimated value of 2.79 × 10⁻⁵ cm² s⁻¹ is the averaged value obtained by two different techniques.