Amperometric detection studies of poly-o-phenylenediamine film for the determination of electroinactive anions in ion-exclusion chromatography

An amperometric detector based on the chemical modification of poly-o-phenylenediamine (P-OPD) on a gold electrode was successfully used for the determination of electroinactive anions (SO₄^2-, Cl^-, NO₃^-, F^-, CH₃COO^- and PO₄^3-) by single-column ion-exclusion chromatography. All of the anions were detected conveniently and reproducibly in a linear concentration range of 1.0 x 10^-5-5.0 x 10^-3 mol L^-1. The detection limits of the anions were 2.10 x 10^-6 mol L^-1 for SO₄^2-, 2.47 x 10^-6 mol L^-1 for Cl^-, 3.53 x 10^-6 mol L^-1 for NO₃^-, 3.41 x 10^-6 mol L^-1 for F^-, 5.82 x 10^-6 mol L^-1 for CH₃COO^- and 3.86 x 10^-6 mol L^-1 for PO₄^3- at a signal-to-noise ratio of 3. The proposed method was successfully applied to the analysis of rainwater and river water samples. The electrode was stable during a 2 week period of operation with no evidence of chemical or mechanical deterioration.