Characterization of an EDTA Bonded Conducting Polymer Modified Electrode: Its Application for the Simultaneous Determination of Heavy Metal Ions

An EDTA bonded conducting polymer modified electrode (EDTA-CPME) was fabricated by polymerization of 3ʹ,4ʹdiamino-2,2ʹ;5ʹ,2ʹʹ-terthiophene monomer on a GCE, followed by the reaction with EDTA in the presence of catalyst. The surface of the resulting modified electrode was characterized with EQCM, ESCA, SEM, Auger electron spectroscopy, scanning Auger microscopy, and electrochemical methods. The amounts of polymer and EDTA attached on the polymer film were determined. Simple immersing of the EDTA-CPME into a sample solution led to the chemical deposition through the complexation with Pb^2+, Cu^2+, and Hg^2+ ions, simultaniously. Various experimental parameters that affect the simultaneous analysis of the metal ions, e.g., EDTA amount, pH, deposition time, and deposition temperature, were optimized. Calibration plots for the EDTA-CPME with square wave voltammetry were obtained in the concentration range between 5.0 × 10^-10 and 1.0 × 10^-7 M for Cu(II) and between 7.5 × 10^-10 and 1.0 × 10^-7 M for Pb(II) and Hg(II). The detection limits for Pb (II), Cu(II), and Hg(II) ions were determined to be about 6.0 × 10^-10, 2.0 × 10^-10, and 5.0 × 10^-10 M, respectively. Interference effects from other metal ions were studied at various pHs and it was found that there was little or no effect on the simultaneous determination. The stability of the EDTA-CPME was remarkably improved by coating the surface with the Nafion film, and the electrode can be used for more than one month. Analytical availability of the EDTA-CPME was demonstrated by the application for the certified standard urine reference material and tap water.