Date of Award
Doctor of Philosophy
Dennis C. Johnson
Pulsed Amperometric Detection (PAD) has proven to be applicable to the determination of a number of organic compounds. One difficulty has been calibration of PAD for quantitative analysis over a wide concentration range. By pairing PAD in series with Conductivity Detection (CD), a much wider linear calibration range was found for carbohydrates and amino acids. Both compound groups were separated via anion-exchange chromatography and detected at Au electrodes;In an attempt to decrease amino acid detection limits, phenylthiohydantoin and methylthiohydantoin derivatives were examined. PAD was found to be more sensitive to these derivatives than the free amino acids. DC amperometry was also applicable to the thiohydantoin derivatives, with no instability or sensitivity loss with time observed. Detection limits as low as two picomoles were determined. Employment of a commercially available C-18 column allowed separation of nearly all amino acids using gradient elution liquid chromatography;Improvement in detection of underivatized amino acids was made by applying Pulsed Coulometric Detection (PCD) and Indirect Coulometric Adsorption Detection (ICAD). Both could be used following separation on anion-exchange columns. PCD was coupled with a glass reference electrode to allow anion-exchange separation of amino acids using gradient elution, and baseline perturbation during the gradient was minimal. Up to 20 amino acids were separated in less than one hour.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Lawrence E. Welch
Welch, Lawrence E., "Electrochemical detection methods for biologically-active molecules " (1988). Retrospective Theses and Dissertations. 8901.