Electrochemical Sensors and Detectors with Renewable Electrode Surfaces

Tenygl, J.

doi:10.1007/978-1-4615-9397-3_7

Cited by 3 publications

(1 citation statement)

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“…Successful applications of pulsed waveforms to carbon electrodes, for the purpose of stabilizing surface activity, have been described by Fleet [27]. However, pulsed waveforms at carbon electrodes do not enable the satisfactory detection of a large variety of polar aliphatic compounds.…”

Section: Historical Developmentsmentioning

confidence: 98%

Pulsed electrochemical detection at noble metal electrodes in liquid chromatography

Johnson

LaCourse

1992

Electroanalysis

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The direct electrochemical detection of numerous polar aliphatic compounds is achieved at Au and Pt electrodes under the control of multistep potential-time waveforms. In this technique, called "Pulsed Electrochemical Detection (PED)," the waveforms manage the sequential processes of sampling the faradaic signal, from the oxidation of analyte, followed by oxidative cleaning and reductive reactivation of the electrode surfaces. The response mechanisms in PED are strongly influenced by surface properties of the electrodes and, therefore, members of each chemical classification detected are observed to produce virtually identical voltammetric response. Consequently, applications of PED have their greatest analytical significance when coupled with Liquid Chromatography (LC) to achieve a priori resolution of complex mixtures. The basic concepts of FED are reviewed and LC-PED results are presented for a variety of samples containing mixtures of alcohols, carbohydrates, alkanolamines, amines, and sulfur compounds. KEY WORDS:Pulsed electrochemical detection? aliphatic compounds, liquid chromatography. IiYZRODUCTION Basic ConceptsIt is common knowledge that aromatic phenols and amines are detected with high sensitivity and reproducibility by anodic mechanisms at conventional solid anode materials (e.g., Au, Pt and C) under constant applied potential [ll. However, in sharp contrast? is the observation that most aliphatic alcohols and amines are not easily detected under these same conditions 01. The observation that aromatic compounds have greater electroactivity than aliphatic compounds is believed to be a consequence of the beneficial decrease in the activation barriers for the anodic mechanisms as a result of the stabilization by pi-resonance of the free-radical products of one-electron oxidations. An inherent electronic mechanism does not exist in aliphatic compounds for stabilization of free-radical oxidation products and the heterogeneous rate constants for their anodic mechanisms at inert anodes are much smaller than for aromatic comThe anodic activation barriers for oxidation of aliphatic compounds are decreased if the radical products of the anodic reactions are stabilized by interaction with active anode surfaces. Such stabilization is possible at electrodes that have unsaturated surface d-orbitals, including clean Au and Pt. However, an undesirable pounds.'To whom correspondence should be addressed.consequence of this interaction is the tendency for these surfaces to become fouled by the accumulation of adsorbed carbonaceous materials. Hence, historical conclusions of nonreactivity for many aliphatic compounds at Au and Pt under conditions of constant applied potential are, in many cases, seen to be a direct consequence of the high catalytic activity of clean metal surfaces which result in fouling of electrodes within a few seconds or minutes.Invariably, the organic species adsorbed on Au and Pt electrodes are oxidatively desorbed quite efficiently by application of large positive potential pulses to gen...

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Section: Historical Developmentsmentioning

confidence: 98%