Electrochemical determination of sildenafil citrate as standard, in tablets and spiked with human serum at gold and cystein modified gold electrode

Abstract

Nonmedical use of sildenafil citrate (SC) requires new methods for drug determination in human serum and in tablets. SC as standard and in Sildena ® tablets is determined by square wave voltammetry (SWV) in 0.1 M H 2 SO 4 (harmful for human serum) at gold electrode in a range: (110 -3 , 110 -2 , 0.1, 0.5, 1) μM and on cysteine (Cys) modified gold electrode (Au/Cys) in a range: (110 -3 , 110 -2 , 0.05, 0.1) μM. The presence of Cys causes two times larger peak currents and shifting of the incipient potential of the SC oxidation to 0.1 V in negative direction. A safe procedure for SC determination as standard and in Sildena ® tablets spiked with human serum is developed by SWV at gold electrode in 0.05 M NaHCO 3 (suitable for human liquids) in a range: (110 -3 , 110 -2 , 0.1, 0.2, 0.3) μM. Microscopic characterization of the surfaces morphology was also performed. The SC concentrations were checked by High Performance Liquid Chromatography-Ultraviolet spectroscopy (HPLC-UV) showing that electrochemical method is more sensitive and can be used for the measurements of very low concentrations of the analyte.

Electrochemical behavior of sildenafil citrate at gold and cystein modified gold electrode in acid solution

“…1 it is show that in the presence of Cys the electrode becomes more active for the electrochemical oxidation of SC. The improved activity of the modified electrode in 0.1 M H 2 SO 4 could be due to the increase of the electrode surface area according to the observed differences in morphology of the gold surface modified with Cys as was confirmed by optical microscope [21]. The role of Cys can also be explained by the mechanism proposed by Ozkan et al for the electrochemical oxidation of SC on a GC electrode in an aqueous solution containing 30 % (v/v) acetonitrile [18].…”

“…As suggested by Wang and Du [22], it seems that Cys act as a mediator of the electrode reaction and as an electron-transferring accelerator. Possible mechanism of interaction between SC and Au/Cys is presented in detailed in [21], explaining the observed reactivity for SC electrooxidation.…”

“…It can be said that highly developed gold oxide on surface is necessary as a catalyst for the beginning of the SC electrooxidation reaction. In order to improve the activity, the electrode was modified with cysteine as was previously described [21]. In the inset of Fig.…”

“…Electrode modification and stock solutions were prepared according to [21]. All the solutions used were prepared with high purity water (Millipore, 18 MΩ cm resistivity).…”

Preparation, Characterization, and Application of Nickel Oxide Nanoparticles in Glucose and Lactose Biosensors

“…Several studies employed the integration of different enzymes on variable electrodes in the development of glucose biosensors (Ang, Por, & Yam, 2015). Lovic et al (Lovic et al, 2018) studied glucose biosensors based on three enzymes: cysteine, glutaraldehyde and glucose oxidase attached to the gold electrode. Yang et al (Yang, Gong, Miao, & Xu, 2017) investigated glucose oxidase and horseradish peroxidase to prepare glucose biosensor depending on carbon nanotubes modified glassy carbon electrode.…”