Simultaneous detection of dopamine and ascorbic acid using polyglycine modified carbon paste electrode: A cyclic voltammetric study

A carbon paste electrode (CPE) was modified by electropolymerisation of glycine in 0.2 M acetate buffer solution (ABS) at pH 5.0. Cyclic voltammetric technique (CV) was used to study the electrochemical properties of the polymer film. The polyglycine modified CPE was used for the electrochemical detection of dopamine (DA) and ascorbic acid (AA). The polyglycine modified CPE showed excellent electrocatalytic activity for the oxidation of DA and AA. Polymer film has negative charges in its backbone, and DA exists as the positively charged species whereas AA exists as the negatively charged one. In cyclic voltammetric measurements favorable ionic interaction (i.e. electrostatic attraction) between DA and polyglycine contributes to the oxidation potential of DA compared to that of bare electrode. The oxidation potential of AA is negatively shifted due to electrostatic repulsion of anionic AA with the polyglycine film. Polyglycine modified CPE exhibited excellent ability to separate DA from AA by means of cyclic voltammetric technique and the separation potential of their anodic peak potential was apart as wide as 0.197 V in pH 5.0 ABS containing 0.1 mM DA and 1 mM AA at the scan rate of 50 mV/s. The detection limit of the current technique was found to be 1 × 10−7 M for DA in the presence of 1 × 10−3 M of AA. Hence this electrode can be used for the selective determination of DA in the presence of high concentration of AA.