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JKMRS Volume 20, No 2, pp 61; An Investigation of the Sample R...
2016년 06월 20일 / 조회수: 654

An Investigation of the Sample Rotation Effects on Suppression of

Convective Flows in PGSE Diffusion NMR Experiments

 

 

Minkyoung Kim1 and Kee-Choo Chung2*

 

 

1Department of Chemistry, Chung-Ang University, Seoul 156-756, Korea, South Korea

2Department of Bioscience and Biotechnology, Sejong University, Seoul 143-747, South Korea

 

 

 

 

Received Apr 12, 2016; Revised May 12, 2016; Accepted May 19, 2016

 


Abstract Undesirable convective flow in an NMR tube inhibits the accurate measurement of diffusion coefficients by NMR spectroscopy. To minimize the convection effects, various methods have been suggested, and it has been known that the use of sample rotation can be useful. However, it has not been clearly examined that the convection suppressing effect of the sample rotation under the different spinning speeds. In this study, the relation between convective flow and the sample rotation was investigated using PGSE NMR diffusion experiments to reveal the feasibility for controlling the convective flow in an NMR tube by sample rotation itself. The viscosity effect was also examined using solvents with four different viscosities, acetone-d6 chloroform-d, pyridine-d5, and D2O.

The sample rotation showed apparent convection suppressing effects at all temperature range for the low viscosity solvents, acetone-d6 and chloroform-d, even at the faster than 5 Hz spinning rate. The similar patterns were also observed for pyridine-d5 and D2O, which have higher viscosity. This effect was observed even at high temperatures where convective flow arises conspicuously.

 

Keywords diffusion, convection, sample rotation, viscosity, volume effect, NMR
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