Extraction of trace analytes by complexation is an efficient technique for voltammetric determination at chemically modified electrodes. Many of the selective ligands used for non-electroanalytical determinations can be employed successfully with chemically modified electrodes, and retain their selectivities in the immobilized form [1,2]. Polymer coating is one of many different methods used to immobilize the modifier onto an electrode surface [3]. In this study, firstly, the glassy carbon electrode was immersed in an aqueous solution of 0.1 M pyrrole containing 10-4 M Alizarin red S (ARS), the electropolymerization was carried out potentiostatically at +0.75 V for the 30 s. During the electropolymerization process, Alizarin red S acts as both the supporting electrolyte and the dopant anion. The electrodes, after electropolymerization, were washed thoroughly with purified water and then subjected to several alternative reduction/oxidation steps in a solution containing 1×10−3M silver nitrate. This salt is the only electrolyte present in solution and acts as both supporting electrolyte and counter ion for the reduction step of the polymer. The reduction/oxidation steps were carried out potentiostatically at −0.4 and +0.5 V, respectively, each step for a period of 300 s. The overall processes repeated three times, ending with an oxidation step of 600 s to remove all the silver species from the PPy membrane. The resulting modified electrodes were directly used for voltammetric measurements. Accumulation of silver into the PPy/ARS film electrode was carried out at a preconcentration potential of -0.6 V vs. Ag/AgCl electrode for a period of 200 s by dipping the modified electrode together with the reference and auxiliary electrodes into a sample solution containing the 1×10−5 M metal ion. The electrode was removed from the accumulation cell, rinsed with water and then transferred to a cell containing 0.2 M potassium nitrate solution adjusted to pH 2.0 for voltammetric measurement. Differential pulse anodic stripping voltammetric (DPASV) experiments were then conducted under quiescent condition. The differential pulse voltammetry was applied in the potential range –0.2 to +0.4 V using a pulse amplitude of 50 mV and a scan rate of 100 mVs−1. The results indicate that templating the electrodes by applying a potential step program to the electropolymerized PPy/ARS membrane in Ag+ electrolyte improves the detectability and selectivity of the electrodes toward silver ion. It seems that by judicious selection of the chelating ligand, and by changing polymerization and templating factors such as film thickness, type of solvent, pH and reaction time, it is possible to induce better selectivity for silver ion.

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