New Modified Electrodes of Graphite paste with Nano Silicon dioxide For Determination of Sildenafil citrate Drug

In this research, new graphite paste electrodes modified with silicon dioxide (SiO2) nano particle are constructed and used for the determination of Viagra drug (Sildenafil citrate, SILC). The electrodes are constructed by preparing ion-pair for (SILC) with phosphotungstic acid (PTA) or phosphomolybdic (PMA) acid using dibutyl phthalate (DBP) as a plasticizer. These electrodes show good sensitivity towards SILC with linear range of (1.010 -7 -1.010 -2 ) M, correlation coefficient, (0.9990) and the life time (120) days for both electrodes, limit of detection (5.17710 -8 and 5.02610 -8 ) M, optimum temperature range (23-50 and 23-65) o C , slope (57.33 and 58.01) mV/decade and optimum pH range (2-6 and 2-5), for SILC-PTA and SILC-PMA electrodes respectively. These electrodes were successfully applied for determination of SILC in pure and pharmaceutical preparation form (tablets) with recovery of not less than 98% .