Angular Flow in Toroid Cavity Probes
NMR signals from samples that rotate uniformly about the central conductor of a TCD (toroid cavity detector) exhibit frequency shifts that are directly proportional to the sample's angular velocity. This newly observed effect is based on the unique radiofrequency field inside TCDs, which is variable in direction. If a liquid sample is pumped through a capillary tube wound about the central conductor, the frequency shift is proportional to the flow rate. A mathematical relationship between a volumetric flow rate and the frequency shift is established and experimentally verified to high precision. Additionally, two-dimensional flow-resolved NMR spectroscopy for discrimination between components with different flow velocities yet retaining chemical shift information for structural analysis is presented. The application of the two-dimensional method in chromatographic NMR is suggested. Furthermore, utilization of the frequency-shift effect for rheologic studies if combined with toroidcavity rotating-frame imaging is proposed.
P. Trautner et al., "Angular Flow in Toroid Cavity Probes," Journal of Magnetic Resonance, vol. 151, no. 2, pp. 284-290, Elsevier, Aug 2001.
The definitive version is available at http://dx.doi.org/10.1006/jmre.2001.2355
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