Principal Investigator: James L. Anderson (The University of Georgia)
Sponsor: GWRI
Start Date: 1986-07-01; Completion Date: 1986-07-01;
Keywords: Water Analysis, Correlation, Electrochemistry, Spectrophotometry
Description:
Theory was developed and experimentally tested for the response of amperometric electrochemical detectors in thin-layer flow channels, and theory was developed and preliminary experiments initiated for the response of spectroelectrochemical correlation detectors in thin-layer flow channels. The theory for amperometric response was evaluated experimentally for several designs of arrays of thin strip microelectrodes in series on one wall of a flow channel, with long axes perpendicular to flow. The electrode arrays were fabricated microlithographically, using gold conductors on silicon dioxide-covered silicon wafers, and platinum conductors on glass or quartz substrates. Experiments were carried out using flow injection methodology with sufficiently large injected volume to insure attainment of steady-state response. Experimental response was in excellent agreement with theoretical prediction, for a series of uniformly spaced arrays of gold microelectrodes with widely varying spacing and number of electrodes. Optimum progression of microelectrode spacing across the array was investigated theoretically. It was shown that the optimum geometry is a uniform array of strip electrodes of equal size and constant spacing. Experimental results support the theoretical conclusion.
Theory was developed for the correlation detector based on electrochemical and spectrophotometric signals generated simultaneously in a thin-layer detector cell. The optimum geometry for the spectrophotometric optical beam was evaluated based on signal/noise considerations, assuming that shot noise was the dominant noise source.
Optimum response is predicted for illumination parallel to the electrode surface and either parallel or perpendicular to flow. Preliminary experiments are qualitatively consistent with theoretical predictions.