Degree Type


Date of Award


Degree Name

Doctor of Philosophy




The design and construction of Au and Pt vibrating electrodes are presented. These electrodes were vibrated by means of a loudspeaker at peak-to-peak amplitudes from 0 to 3.3 mm and frequencies from 30 to 510 Hz. Electronic instrumentation is described which permitted direct recording of the limiting current as a function of the vibrational amplitude. This instrumentation was also used to effect hydrodynamic modulation at the vibrating electrode, with phase-selective detection of the resultant 10-Hz alternating component of the electrode current;The hydrodynamic behavior of vibrating electrodes was studied visually and electrochemically. Hydrodynamic transitions in the flow patterns induced by the vibrating electrodes were characterized. The exponential dependences of the limiting current on the vibrational parameters were determined;The analytical determination of Br('-), Cr(,2)O(,7)('2-), and O(,2) at submicromolar levels was demonstrated using hydrodynamic modulation at a Pt vibrating electrode;The vibrating electrode was employed in flow-injection analysis for the determination of I('-). A detection limit of 5 x 10('-10) M I('-) was demonstrated for a signal-to-noise ratio of 2. A linear dynamic range from 1 x 10('-3) M to 5 x 10('-10) M I('-) was observed. Equations are derived which describe the performance of the vibrating electrode in flow-injection analysis for both steady-state conditions and plug injection of samples. The validity of the fundamental assumptions, upon which these equations are based, is evaluated. Hydrodynamic modulation at the vibrating electrode in flow-injection analysis was shown to discriminate against the charging current normally observed at amperometric flow-through electrodes following a change in potential;Determinations of Hg(II) in Lake Superior water were performed at the part-per-trillion level, using a Au vibrating electrode in differential pulse anodic stripping voltammetry. The estimated detection limit for a signal-to-noise ratio of 2 was 2 x 10('-11) M Hg(II) (4 pptr). The limiting factor in the analytical determination was the highly variable background level of Hg noted in the reagents employed in the procedure.



Digital Repository @ Iowa State University,

Copyright Owner

Kenneth W. Pratt, Jr.



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290 pages