The primary difficulty for successful LC - ¹³C NMR (whether ¹H or ¹³C) is overcoming the relatively low sensitivity of NHR as a chromatographic detector. For the ¹H nuclide this is much less of a problem; the sensitivity ;s approximately 6000 times more sensitive than that of ¹³C nuclei. For this reason, much of the literature focuses on LC - ¹H NMR. To ever successfully realize LC - ¹³C NMR, it is mandatory that an augmentation of ¹³C signal intensity must be effectuated to overcome this sensitivity deficit (~ three orders of magnitude). To satisfy this requirement, our laboratory has utilized dynamic nuclear polarization (DNP) to ameliorate these otherwise weak or non-existent signals. For favorable molecules, sensitivity recoveries of up to two orders of magnitude have been developed. This improvement (relative to 'H) narrows the sensitivity gap between 'H and ¹³C NMR detection of chromatographically separated analytes. Despite the fact that relatively large injection volumes were required in most LC experiments, the wealth of structural information inherent to ¹³C NMR justifies any attempt to successfully couple nuclear magnetic resonance to liquid chromatography.
In addition, DNP was utilized in a series of SLIT and LLIT experiments where a test mixture was recycled through a NMR spectrometer. Results indicate that ¹³C spectra were obtained with a significantly higher signal-to-noise ratio in a shorter amount of analysis time relative to experiments where DNP was not employed for signal enhancement. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/44860 |
| Date | 19 September 2009 |
| Creators | Stevenson, Steven A. |
| Contributors | Analytical Chemistry, Dorn, Harry C., Anderson, Mark R., Taylor, Larry T. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | xv, 147 leaves, BTD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 27690884, LD5655.V855_1992.S748.pdf |
Page generated in 0.0112 seconds