Amperometric detection and electrochemical oxidation of aliphatic amines and ammonia on silver-lead oxide thin-film electrodes

Ge, Jisheng
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Research efforts have been devoted in discovering new anode materials for obtaining stable and sensitive amperometric and voltammetric signal when applied at constant or triangle waveform potentials for oxidation of aliphatic amines. Voltammetric and amperometric results were compared for detection of selected organic amines in carbonate buffer (pH 10) at mixed silver-lead oxide film prepared by electrodeposition and anodization of Ag-Pb alloys and found that anodized alloys specifically eutectic alloy are superior with regard to stability of response. Linear dynamic range, sensitivity and long term stability of the electrode for detecting selected primary amine, secondary amine, tertiary amine, alkanolamines and amino acids under constant applied potentials were estimated by flow injection detection method. The kinetic heterogenous electron transfer rates for the oxidation of ethylamine, alanine and ammonia at anodized eutectic alloys at elevated temperatures were studied by voltammetry at a jacket three-compartment cell or by electrolysis at a home-made flow-through reactor. The oxidation products of electrolysis of ethylamine, alanine and ammonia were determined by GC-MS, Ion Chromatography, N-15 NMR through solvent extraction, head-space and isotope enrichment samplings in order to study reaction pathways and Faraday processes. Structure, composition and morphology of surface oxide films formed on anodized alloys were characterized by XRD, XPS, SIMS, STM, SEM, and EDS. The common phenomena of peak shapes observed from voltammetric responses in anodic region were explained in terms of competition consumptions of electrode surface generated hydroxyl radicals from water discharging by either oxygen evolution or oxygen transfer reactions to higher oxidation products. Further supporting evidences were found from linear plots of peak potentials with respect to natural logarithm of either amine concentration or square root of electrode rotation velocity which can be theoretically formulated by assuming that at peak potentials the flux of hydroxyl radical generation is equal to the flux of product formation.

Chemistry, Analytic, Chemistry