Convection Effects on PGSE-NMR Self-Diffusion Measurements at Low Temperature: Investigation into Sources of Induced Convective Flows

Abstract

The effects of convection on the measurement of the diffusion coefficients of liquids by the pulsed gradient spin echo (PGSE) NMR method at low temperature are discussed. To examine the generation of convective flows, we used four different types of sample tubes in the diffusion measurements with temperature variation; a normal 5 mm NMR tube, a Shigemi tube, an ELISE type tube, and a capillary tube. Below room temperature, the calculated diffusion coefficients of chloroform in 5 mm o.d. type tubes increased with decreasing temperature, while those in the capillary tube decreased linearly. The convective flow was found to be significant even at low temperature and it seemed to be mainly induced by the transverse temperature gradient. It was also found that the capillary tube was most appropriate to measure the diffusion coefficients, since its small diameter is effective in suppressing the convective flows at both high and low temperatures.

Diffusion of hyperpolarized 13C‐metabolites in tumor cell spheroids using real‐time NMR spectroscopy

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PFG-NMR and MD Simulation Study of Self-Diffusion Coefficients of Binary and Ternary Mixtures Containing Cyclohexane, Ethanol, Acetone, and Toluene

“…The spectrometer's temperature sensor was calibrated with a platinum resistance thermometer (Pt-100) that was, in turn, calibrated in our laboratory using a certified standard. The standard uncertainty of the temperature measurement is estimated as u(T) = 0.1 K. Special sample tubes with an outer diameter of 2.5 mm (Deutero GmbH, Germany) were used in order to minimize sample convection 41 and radiation damping. 42 A stimulated spin−echo technique with bipolar pulsed gradients 43 was applied as implemented in the NMR spectrometer's software (pulse sequence: stebpgp1s).…”

Self‐Diffusion Coefficients in Solutions of Lithium Bis(fluorosulfonyl)imide with Dimethyl Carbonate and Ethylene Carbonate

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