Multiple -coil nuclear magnetic resonance probes for high -throughput and difference spectroscopy
Abstract
Advances in nuclear magnetic resonance (NMR) spectroscopy are often driven by the development of novel hardware and software. In this thesis, three new probes for high-throughput and difference spectroscopy are presented. The Multiplex NMR Probe is a four-coil NMR probe that can analyze four samples simultaneously and in rapid succession. An automated sample handling and analysis routine for high-throughput NMR was developed to simultaneously inject four samples into the Multiplex Probe and achieved an analysis rate of almost two samples per minute for 1D 1H NMR. Two probes were developed for NMR difference spectroscopy. The Difference Probes have the ability to acquire a single, difference spectrum from two samples simultaneously. The dual-coil probes have a unique radiofrequency circuit that generates a phase difference between the two samples' NMR signals by switching the relative orientation of the radiofrequency transmitter and receiver during the NMR experiment. Crossed-diodes can be used as passive switches or single diodes can be used with an active bias circuit to create the necessary switching function during the NMR experiment. One Difference Probe was constructed with solenoidal-geometry micro detection coils and flow capabilities. Two samples containing a common analyte, were used to demonstrate signal cancellation in a difference spectrum collected with a single pulse experiment. The cancellation was over 96% effective. The approach described has applications in the areas of solvent subtraction, spectral simplification, and liquid chromatography (LC)-NMR. The second Difference Probe was constructed with saddle-shaped detection coils and uses a specially modified 3 mm NMR tube to hold the two samples. The degree of cancellation of common signals was determined to be approximately 90%, and the application of the probe to relaxation-edited difference spectroscopy for identifying protein-ligand interactions was demonstrated.
Degree
Ph.D.
Advisors
Raftery, Purdue University.
Subject Area
Analytical chemistry
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