VOLTAMMETRIC DETERMINATION OF VARDENAFIL ON MODIFIED ELECTRODES CONSTRUCTED BY GRAPHITE, METAL OXIDES AND FUNCTIONALIZED MULTI-WALLED CARBON NANOTUBES

Abstract

The voltammetric behavior of the vardenafil was investigated by means of square wave stripping voltammetry (SWSV), differential pulse stripping voltammetry (DPSV) and cyclic voltammetry (CV) on the modified electrodes constructed by graphite, metal oxide and functionalized multi-walled carbon nanotubes (MWCNT).Different experimental conditions were optimized such as pH and electrolyte type, accumulation potential and accumulation time for both techniques and step potential, pulse amplitude and frequency for SWSV. In the optimum conditions a linear relationship has been constructed in the concentration range of 0.02 to 1.0 mg/L and 0.01 to 0.5 mg/L for SWSV and DPSV in pH 3.0 phosphate buffer solution, respectively. Limit of detection (LOD) values for vardenafil determinations were13.6 mu g/L and 4.38 mu g/L for SWSV and DPSV, respectively. Quantifications were performed on commercial pharmaceutical tablets and synthetic blood serum using both techniques. The relative errors were +5.0% and -3.0% for SWSV and DPSV, respectively in the determination of vardenafil active ingredient in Levitra (R) tablet. SWS and DPS voltammetric determination of synthetic blood serum spiked with 50.0 mu g/L vardenafil exhibited 100.8% and 104.4% recovery, respectively. Interference effects of some organic species such as ascorbic acid, uric acid, dopamine, glucose have also been investigated.