Simultaneous Voltammetric Determination of Dopamine and Ascorbic Acid with Polyglycine Modified Carbon Black Microelectrode

Polyglycine modified carbon black microelectrode was prepared by electrochemical polymerization of glycine on the surface of the electrode in PBS of pH 7.0,and electrochemical behavior of this modified electrode were studied by cyclic voltammetry.It was found that in PBS of pH 7.0,dopamine and ascorbic acid after their accumulation at -200 mV (vs.SCE) for 30 s,were oxidized catalytically at the modified electrode with their peak potentials (Epa) at 320 mV and 42 mV respectively.Linear relationships between values of I″p and concentration of dopamine and ascorbic acid were obtained in the ranges of 2.0×10-8-1.0×10-4mol·L-1 and 4.0×10-7-1.0×10-3mol·L-1 respectively,with detection limits (3σ) of 6.0×10-9mol·L-1 (for dopamine) and 1.0×10-7mol·L-1 (for ascorbic acid).The modified electrode behaved with good repeatability and stability,as well as easy resumption of its function by cleaning in the same buffer solution at 400 mV for 0.5-2.0 min.The proposed method has been used in analyzing solutions containing both dopamine and ascorbic acid,giving values of recovery and RSD′s (n=7) in the ranges of 96%-104% and 1.6% to 2.6% respectively.