In this study, the main purpose is to fabricate a sensitive and selective electrochemical sensor through the multiwalled carbon nanotube-graphite/Ag electrode (MWCNTs-G/Ag). The application of this sensor was developed for the determination of diclofenac sodium in pharmaceutical dosage form, urine and human plasma. MWCNTs-graphite mixture improved the electroactive surface area due to its porous structure and a remarkable increase in the peak currents was observed. It demonstrated a catalytic effect and speeded up the rate of redox process. Application of MWCNTs-G/Ag resulted in a sensitivity augmentation. It is found that a maximum current response for the sensor in the Britton-Robinson buffer solution can be obtained in pH 3. The prepared sensor showed good standard calibration curves during 3 consecutive days over the concentration range of 45-2000 ng/mL and RSD values ranging from 1.95-7.11%. The limit of quantitation and detection limit were 45 and 15 ng/mL, respectively.

The development of an electrochemical sensor for determination of mefenamic acid is the main purpose of this work. The determination was performed in pharmaceutical formulations, spiked urine and human plasma samples by multi-walled carbon nanotube-graphite/Ag (MWCNTs-G/Ag) electrode. Hence some voltammetric methods were investigated to determination of mefenamic acid. The dependence of peak currents and potentials on pH and voltammetric parameters was investigated for the optimization of electrochemical method. The porous structure of MWCNTs-graphite mixture improves the electroactive surface area. As a result, a remarkable increasing in the peak currents was observed. The prepared mixture displayed an electrocatalytic effect in anodic oxidation of mefenamic acid with a sensitivity augmentation. The best electrochemical response was obtained from square wave voltammetry with a sensitive peak at 0.68 V in pH 5. The prepared electrode showed good standard calibration curves during 3 days over a wide concentration range with RSD values ranging from 1.6-8%. The limits of quantification and detection were 50 and 16 ng/mL, respectively.