| Summary: | Electrochemical behavior of sildenafil citrate (SC) at gold and cystein (Cys) modified gold electrode (Au/Cys) in 0.1 M H2SO4 was investigated by cyclic voltammetry (CV) and by square wave voltammetry (SWV). Effect of scan rate on the CVs of SC standard was performed in order to examine the mode of transport and irreversibility of process. SC as standard is determined by SWV in acid solution at Au electrode in a range: 10-3, 10-2, 0.1, 0.5, 1 μM and on Au/Cys in a range: 10-3, 10-2, 0.05, 0.1 μM. The presence of Cys causes two-time larger peak currents and shifting of the incipient potential of the SC oxidation to 0.1 V in negative direction. In investigated range of concentration of SC standard in acid solution on modified and unmodified Au electrodes SWV method have excellent linear regression coefficient with value 0.997 promoting SWV for reliable determination of SC.
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