Date of Award
Doctor of Philosophy
It is the general experience that most organic compounds including organic amines do not produce reversible anodic waves at Pt electrodes. Furthermore, amperometric detection of these compounds at a constant potential fails due to the accumulation of adsorbed reaction products and/or an oxide film at the electrode surface. Pulsed Amperometric Detection (PAD) restores surface activity through the use of a triple-step potential waveform in which detection, cleaning, and analyte adsorption potentials are applied alternately. The analytical signal is sampled within a few milliseconds after application of the detection potential, and held in electronic memory through the remainder of the pulsed potential sequence. This procedure makes possible the sensitive detection of species that adsorb at Pt electrodes. Analytical response is concluded from experiments with CN('-) and Cl('-) to depend upon the Langmuir adsorption isotherm for the analyte species detected. Hence, the calibration plot of 1/I(,p) vs. 1/C(,b) is linear for low surface coverages by the adsorbed analyte;Primary, secondary, and tertiary aliphatic amines, all amino acids (including secondary amino acids), and aminoglycosides are detectable. Results are shown for the direct amperometric detection of amino acids by anion exchange chromatography using NaOH as the eluent and supporting electrolyte. The detection limits are comparable to those obtained by OPA detection methods (i.e. ca, 100 ppb), and no post-column addition of reagent is necessary. Chromatographic analyses of aminoglycoside antibiotics in production broths and blood serum are also demonstrated.
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John A. Polta
Polta, John A., "Pulsed Amperometric Detection: a method for detecting amines in liquid chromatography " (1985). Retrospective Theses and Dissertations. 7880.