Ion-exchange voltammetry at poly(ester-sulfonic acid) film coated electrodes for trace analysis

Abstract

Ion exchange voltammetry at poly(ester-sulfonic) acid coated electrodes allows convenient trace and ultratrace measurements of large hydrophobic cations. Rotating glassy carbon electrodes coated with new Eastman AQ-55D and AQ-29D ionomers are used to collect such ions electrostatically from dilute solutions prior to voltammetric analysis. The effects of various variables of the preconcentration/voltammetry/regeneration scheme, including rotation speed, exposure time and scan parameters, are assessed. “Analyte-free” surfaces could be obtained rapidly by reversing the ion-exchange process. Various advanced voltammetric waveforms are explored for the quantitation of the surface-bound analyte, with a computerized background subtraction differential pulse scan providing the lowest detection limit (4 × 10 −10 M). Linear calibration plots are obtained at the submicromolar concentration level following short (< 60 s) preconcentration times. For successive measurements of 2.5 × 10 −7 M methyl viologen cation the response could be reproduced with a 4.9% relative standard deviation. The coated electrodes are simple and inexpensive to prepare and are stable.