This dissertation investigates three major problems in IC, ranging from the practical to the theoretical. The first is of interest to the field of quantitative analysis. Since ion chromatography is primarily a quantitative technique, the linear range of the detector is of particular interest. The linear range was determined to be nearly five orders of magnitude for several common ions. The probes used were fluoride, chloride, sulfate, sodium, and potassium with concentrations ranging from 10 ppb to 1000 ppm. This portion of the dissertation describes the first attempt made to elucidate the linear detection range in ion chromatography using micro-membrane suppression.
The Iinearity experiments demonstrate the versatility of ion chromatography with respect to quantifiable concentrations. However, a major problem is encountered when attempting to determine a trace ion concentration in the presence of a high concentration of a similarly charged ion (matrix ion). The second part of this dissertation offers a solution to this problem. In ion chromatography, the large excess of a matrix ion affects not only the ions expected in that region of the chromatogram, but also destroys the chromatographic exchange process. One objective of this study was to develop a rapid quantitative method to determine 5 ppm chloride in the presence of 100,000 ppm sulfate. A standard anion exchange column will completely lose resolution between chloride and sulfate at a sulfate concentration of approximately 2500 ppm. The apparatus designed and built by the author uses two analytical ion—exchange columns coupled in series by a high pressure switching valve. ln order to complete the system, the author designed and built y a high pressure conductivity detector cell to monitor the conductivity of the effluent from the first column. The system works by overloading the first column and then allowing the effluent to pass onto the second column. When the trace chloride in on the second column, the first column is switched out of line. This process allows the trace chloride to be separated from the residual sulfate.
The column switching study brought to light several theoretical questions about the inner workings of the packing materials used in ion chromatography. These questions include the effects that flow rate and temperature have on capacity and efficiency in ion chromatography separations. Using chloride and sulfate as probes, the chromatographic efficiency was shown to decrease from 30° to 60° C. Even more surprising was the result that sulfate retention increased with increasing temperature while chloride retention decreased under the same conditions. Detailed studies as well as possible explanations are included in the third part of this dissertation. / Ph. D.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/54338 |
| Date | January 1988 |
| Creators | Polite, Lee Nicholas |
| Contributors | Chemistry, McNair, Harold M., Dillard, John G., Long, G.L., Mason, John G., Bell, Harold M. |
| Publisher | Virginia Polytechnic Institute and State University |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation, Text |
| Format | viii, 108 leaves, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 19736155 |
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