Date of Award
Doctor of Philosophy
Methods are described for the electrochemical detection of several classes of electroactive elements and compounds utilizing pulsed waveforms in flow-injection and liquid chromatographic systems. Particular emphasis is placed on the development of waveforms for the rejection of ubiquitous background interferences as well as for the enhancement of sensitivity and detectability;Constant potential pulse polarography is described for the determination of reversible electroactive ions, such as Cd(II), Cu(II) and Pb(II), in the presence of dissolved oxygen with no apparent interferences;Pulsed amperometric detection (PAD) is described for the detection of carbohydrates with an asymmetric two-step waveform at a gold electrode in alkaline media, without a loss in sensitivity in comparison to three-step waveforms. PAD schemes based upon the use of a gold electrode instead of platinum are presented with special emphasis on the amperometric detection of carbohydrates in alkaline solutions;Pulsed coulometric detection (PCD) at a constant detection potential was introduced to increase the overall linear dynamic range for the detection of carbohydrates through a lowering of detection limits. PCD at swept detection potentials was developed to reduce automatically background signals resulting from oxide formation and double-layer charging at noble metal electrodes and thus eliminates the need for special offset compensation circuitry. The background drift commonly observed with PAD as a result of electrode surface reformation processes was eliminated. In addition, the background signal was found to be virtually independent of small changes in eluent pH, and thus may be used in liquid chromatographic schemes which employ pH-step or pH-gradient elution;Pulsed coulometric detection was also extended to the determination of heavy metal ions which are reversibly reduced at a gold electrode. Limits of detection for most metals, e.g., Hg(II), Bi(III), Pb(II), and Cd(II) are 0.1-10 (mu)M for a two-step waveform applied with a frequency of 1 Hz.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Glen Gary Neuburger
Neuburger, Glen Gary, "The development of pulsed waveforms for the electrochemical detection of inorganic and organic compounds in flow-injection analysis and liquid chromatography " (1987). Retrospective Theses and Dissertations. 8570.