Voltammetric determination of dopamine in the presence of uric acid using a 2-hydroxy-1-(1-hydroxynaphthyl-2-azo)- naphthalin-4-sulfonic acid modified glassy carbon electrode

A polymerized film of 2-hydroxy-1-(1-hydroxynaphthyl-2-azo)-naph- thalin-4-sulfonic acid (HHNANSA) was prepared at the surface of a glassy car- bon electrode by electropolymerization. The modified electrode was used for the simultaneous determination of dopamine (DA) and uric acid (UA). The electrochemical behaviors of the compounds at the surface of the modified electrode were studied using cyclic voltammetry, chronoamperometry, and square wave voltammetry (SWV). The experimental results indicated that the modified electrode exhibited an efficient electrocatalytic activity towards the oxidation of DA and UA, with a peak separation of about 140 mV at pH 5.0. Using chronoamperometry, the catalytic reaction rate constant was measured and found to equal to 1.23×10 4 mol -1 L s -1 . At pH 5.0, the catalytic peak cur- rents linearly depended on the DA and/or UA concentrations in the range of 1.0-300 µmol L -1 DA (two linear segments with different slopes) and 6.7-20 µmol L -1 UA, using SWV. The detection limits for DA and UA were 0.25 and 1.17 µmol L -1 , respectively. The RSD % for 40.0 and 140.0 µmol L -1 DA were 1.9 and 2.2 %, respectively, whereas for 10.0 and 20.0 µmol L -1 UA, they were 1.8 and 1.2 %, respectively. The modified electrode showed good sensitivity, selectivity, and stability. It was successfully applied for the determination of DA and UA in real samples, such as drugs and urine.