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EDWARD DWIGHT KINGSLEY, University of Massachusetts Amherst


The work presented is divided into three sections. The first describes the study of ac voltammetric methods in flowing streams. The objective was to determine the dependence of the ac current on concentration, frequency, ac amplitude and dc scan rate for static and flowing conditions. The goal was to show that the ac current would be independent of the flow rate under the proper experimental conditions. The ac voltammetric experiment was shown to be independent of the flow rate over the entire range of flow rates studied. The second section describes the design and development of an ac electrochemical instrument that uses a lock-in amplifier with phase sensitive detection. A phase sensitive detector was designed that utilizes digital counting techniques and precision phase shifting circuitry to optimize the measurement of the faradaic signal in the presence of the capacitive background. The goal was to improve the detection limits for ac electrochemical measurements ten to one-hundred fold. Electrical measurements were made to evaluate performance characteristics, such as minimum detectable signal, dynamic range, dynamic reserve and phase angle resolution. The results from the electrical characterization data showed that the lock-in amplifier with digital phase sensitive detection performed very closely to design specifications. The final section describes a study made to evaluate the performance of the new ac electrochemical instrument in making actual ac electrochemical measurements. AC linear scan and amperometric experiments were performed on a reversible redox system, the ferri-ferrocyanide couple, at a carbon paste electrode. The object was to determine detection limits for these experiments with the new instrumentation. The detection limits obtained for the ac electrochemical experiments are 10 to 50 times better than previously reported detection limits for ac methods.

Subject Area

Analytical chemistry

Recommended Citation

KINGSLEY, EDWARD DWIGHT, "INSTRUMENTATION FOR AND STUDIES IN A.C. VOLTAMMETRY" (1983). Doctoral Dissertations Available from Proquest. AAI8310303.