Date of Award

Fall 1995

Project Type

Dissertation

Program or Major

Chemistry

Degree Name

Doctor of Philosophy

First Advisor

Sterling Tomellini

Abstract

A significant limitation of ATR/FTIR for the analysis of aqueous solutions is the relatively high bulk concentration of analyte required. One approach to improving the detection of an analyte is to incorporate a thin polymeric phase at the surface of the ATR element. The purpose of the polymeric phase is to extract the analyte of interest and concentrate it within the depth of penetration of the evanescent wave. Utilizing a very high molecular weight poly(vinyl chloride) phase the time necessary to reach equilibrium for a 0.05% (v/v) nitrobenzene in a 1.5% (w/v) methanol/water solution was over 60 minutes. A study was undertaken to determine if incorporating a plasticizer into the polymeric phase reduces the time required to reach the maximum level of absorbance achieved for the analyte. Specifically, the ability of phases which are mixtures of PVC and chloroparaffin plasticizers to concentrate analytes from aqueous solutions has been investigated. The results indicate that incorporating chloroparaffin into a PVC phase reduces the time required to reach the maximum absorbance for the analyte in an aqueous solution containing 1.5% methanol by approximately 45%. The addition of chloroparaffin also results in an increase in the absorbance observed for the analytes investigated in this study.

Commercially available untapered and tapered chalcogenide fibers have been coated with poly(vinyl chloride) with plasticizer. These coated fibers were exposed to various analytes. All organic analytes provided readily detectable signals with the coated fibers but were not observable when the aqueous solution was sampled with the use of uncoated fibers. The results confirm the advantages of using a polymer coating to concentrate the analyte and reduced the water background for detecting non polar organic solutes in aqueous solutions.

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