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"Angular Flow in Toroid Cavity Probes"
P. Trautner, K. Woelk, J. Bargon,
and R.E. Gerald II,
J.
Magn. Reson. 151, 284-290 (2001).
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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.
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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 is presented for discrimination
between components with different flow velocities yet retaining chemical
shift information for structural analysis.
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The application of the two-dimensional method in chromatographic NMR is
suggested. Furthermore, utilization of the frequency-shift effect is proposed
for rheologic studies if combined with toroid-cavity rotating-frame imaging.
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K. Woelk, December
21, 2001