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

- Clinical needs caused the new method development for SC determination.
- SWV method for SC standard, tablet and in human serum in 0.05 M NaHCO3 is applied.
- In 0.1 M H2SO4 for SC standard and tablet catalytic effect of Au/Cys is observed.
- SWV is more sensitive than HPLC and can be used for very low concentrations of SC.
- Microscopic characterization of the morphology of the used electrode surfaces.

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 H2SO4 (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 NaHCO3 (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.

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