Flow Injection Bi-amperometric Determination of Diclofenac Sodium with Chitosan/Multi-Walled Carbon Nanotubes Composite Film Modified Paraffin Soaked Graphite Electrode

The chitosan-multi-walled carbon nanotubes composite film modified paraffin soaked graphite electrode (abbreviated CS-MCNT′s/GE) was prepared,and the electrochemical behavior of diclofenac sodium (DS) at this modified electrode was studied by cyclic voltammetry.Based on the catalytic oxidation of DS at CS-MCNT′s/GE,and on the principle of bi-amperometric detection of irreversible electrode reaction,a method of direct FI-biamperometric determination of DS was proposed.In the bi-amperometric detection system,when a potential of 0 V was applied,irreversible catalytic oxidation of DS was carried out at CS-MCNT′s/GE,and irreversible reduction of MnO-4 carried out at the other Pt-electrode in a phosphate buffer solution of pH 6.8.Linear relationship between the oxidation peak currents and concentrations of DS was obtained in the range of 8.0×10-7-2.0×10-4mol·L-1,with detection limit (3S/N) of 2.0×10-7mol·L-1.Test for precision was performed at 1.0×10-5mol·L-1 DS,the values of RSD (n=20) found was 4.75%.Using DS tablet sample as matrix,recovery test was made by standard addition method,the values of recovery were found in the range of 98.0%-105.5%.