Development and Application of Improved Methods for Coupling NMR and Capillary Isotachophoresis

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Professor Cynthia Larive of the University of Kansas is supported by the Analytical and Surface Chemistry program for development of capillary isotachophoresis (cITP) in combination with microcoil NMR spectroscopy. The development of solenoidal microcoils with nanoliter to microliter detection volumes has greatly enhanced the mass limits of detection of nuclear magnetic resonance (NMR). Recently, this technology has been advanced further through the coupling of capillary isotachophoresis (cITP) for sample concentration and analyte separation with nanoliter microcoil NMR probes for on-line detection. This new methodology shows considerable promise as a versatile tool for the analysis of mass limited samples. The proposed research will advance the instrumentation for online cITP-NMR and explore the application of this methodology to chemical analysis. A capacitively coupled conductivity detector for use in conjunction with NMR detection will be developed and evaluated. The implementation of dual conductivity and NMR detection for cITP will advance this technology by facilitating the use of signal averaging to detect dilute analytes with NMR and monitor NMR transparent cITP bands. This technology will be critically evaluated as a tool for the analysis and structure elucidation of mass limited samples through the examination of several antibiotic compounds both as simple mixtures and in the presence of more complex sample matrices. Finally, this approach will be used to characterize the structure, chemical and physical properties of humic substances through cITP fractionation as a function of pH and borate complexation as well as with one and two-dimensional NMR experiments. These experiments will examine functional group composition of the fractionated materials allowing interpretation of both common and unique structural elements of the bands separated by cITP. The development of new measurement techniques has facilitated understanding of many complex chemical phenomena. This has been particularly true in the field of environmental chemistry, where scientists face the problem of analyzing very complex samples containing species at low concentrations. The proposed experiments will develop new analytical methods that will allow NMR characterization of molecules at low concentrations in complex samples. NMR is one of the most informative methods of chemical analysis, capable of revealing minute details of molecular structure. Initial experiments will focus on relatively simple samples of antibiotics, compounds of environmental interest due to their wide spread use in large scale agriculture and problems related to the development of antibiotic resistance. In addition, cITP-NMR technology will be used to study a class of environmentally important compounds, humic substances (humic and fulvic acids). Humic substances are environmentally important because they affect the bioavailability and transport of organic pollutants and toxic metal ions. These naturally occurring organic acids are formed in the environment by the breakdown of animal and plant material to form very complex mixtures, which makes the determination of molecular level structure information very difficult. These experiments will advance the knowledge of the chemistry of humic substances and in turn increase the understanding of their behavior in the environment.