Nuclear Magnetic Resonance as a Tool to Study Flow

Fukushima, Eiichi

doi:10.1146/annurev.fluid.31.1.95

Cited by 280 publications

(162 citation statements)

References 76 publications

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“…22 However, in the microscopic regime, the diffusion of fluid molecules must also be taken into account, otherwise a significant source of error is introduced for flow with small Reynolds numbers. 23,24 Measurements of both diffusion and flow can be encoded in a so-called q-space imaging experiment. [25][26][27] In its most common implementation, a standard pulsed-field gradient spin-echo (PGSE) experiment is used.…”

Section: Nmr Microimaging Of Flowmentioning

confidence: 99%

Magnetic Resonance Microimaging and Numerical Simulations of Velocity Fields Inside Enlarged Flow Cells Used for Coupled NMR Microseparations

Zhang

Webb

2005

Anal. Chem.

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The coupling of various chemical microseparation methods with small-scale NMR detection is a growing area in analytical chemistry. The formation of enlarged flow cells within the active volume of the NMR detector can significantly increase the coil filling factor and hence the signal-to-noise ratio of the NMR spectra. However, flow cells can also lead to deterioration of the separation efficiency due to the development of complex flow patterns, the form of which depend on the particular geometry of the flow cell and the flow rate used. In this study, we investigated the flow characteristics in different flow cell geometries relevant to the coupling of capillary liquid chromatography and NMR. Computational fluid dynamics was used to simulate fluid flow inside flow cells with a volume of ~ 1 µL. Magnetic resonance microimaging was used to measure experimentally the velocity fields inside these flow cells. The results showed good agreement between experiment and simulation and demonstrated that a relatively gradual expansion and contraction is necessary to avoid areas of weak recirculation and strong radial velocities, both of which can potentially compromise separation efficiency.An essential component in the purification and analysis of unknown compounds is efficient separation of individual components from an often complex chemical or biological system. Advances in microseparations, include techniques such as capillary liquid chromatography (cLC), 1 capillary electrophoresis (CE), 2 and capillary electrochromatography 3 have played a large role in improving the separation efficiency. The chromatographic dilution (D) of cLC, for example, is given by (1) where C 0 is the initial concentration of the analyte, C max is the final compound concentration at the peak maximum, r is the column radius, ϵ is the column porosity, k is the retention factor, L is the column length, H is the column plate height, and V inj is the injected sample volume. Equation 1 shows that a smaller column radius results in less chromatographic dilution and higher concentration elution peaks. The smaller scale is also much more amenable to very rapid separations. In addition to these general benefits of microseparations, in electrophoretic separations the high surface area-to-volume ratio of the small capillaries used in CE systems,

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Section: Nmr Microimaging Of Flowmentioning

confidence: 99%

Magnetic Resonance Microimaging and Numerical Simulations of Velocity Fields Inside Enlarged Flow Cells Used for Coupled NMR Microseparations

Zhang

Webb

2005

Anal. Chem.

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“…Most mixing applications operate in the rolling regime, which for large particles is characterized by a smooth, steady flow with a nearly flat inclined surface. Granular flow measurements obtained using magnetic resonance imaging (MRI) by Eiichi Fukushima and others 11 indicate that, in the rolling regime, flow in a radial-azimuthal slice through the drum occurs in two distinct regions. In a thin layer near the top of the bed, particles follow nearly parallel downhill trajectories.…”

Section: Flow Regimesmentioning

confidence: 99%

Nonequilibrium Patterns in Granular Mixing and Segregation

2000

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For over 5000 years, granular mixing has been a topic of acutely practical concern. Paleolithic cave painters mixed their colors from blends of ochre and animal products; ancient Chinese and Egyptians blended inks and cosmetics from pork soot, crushed pearls, and compounds of lead; Aztec priests prepared drugs from concoctions of herbs and roots; and Michelangelo pigmented the Sistine chapel frescoes with blends including chalk, charcoal, and lead.

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“…For the NMR signal to be encoded for position, magnetic field gradient pulses of a specific length are used (Fukushima, 1999). The relative peak integral of a particular proton at a specific position in the sample will change over time and this change is attributed to the displacement of the molecules due to diffusion.…”

Section: Introductionmentioning

confidence: 99%