Nuclear magnetic resonance diffusion measurements

Like nuclear magnetic resonance, dynamic light scattering uses expensive equipment for a relatively easy measurement of the diffusion coefficient. Like nuclear magnetic resonance, the measurement requires no initial concentration difference, and so is especially suited to viscous solutions. Unlike nuclear magnetic resonance, the measurement is of the binary coefficient, not the tracer diffusion coefficient. 

Balcom, B Fischer, A Carpenter, T Hall, L, Diffusion in Aqueous Gels. Mutual Diffusion Coefficients Measured by One-Dimensional Nuclear Magnetic Resonance Imaging, Journal of the American Chemical Society 115, 3300, 1993. 

Several mechanisms are involved in the permeability through Caco-2 cells. In order to obtain a more pure measure of membrane permeability, an experimental method based on ghost erythrocytes (red blood cells which have been emptied of their intracellular content) and diffusion constant measurements using nuclear magnetic resonance (NMR) has been proposed [108]. 

Nuclear magnetic resonance measurements of methane adsorbed to various coverages on titanium dioxide have been made by Fuschillo and Renton 16). At a coverage of 0.95 monolayer and at 20.4°K, the X-point for solid bulk methane, these authors observed an abrupt change in the proton resonance line width, presumably due to translational and rotational diffusion of methane molecules. For pure, bulk methane no change has been observed in the line width at the X-point. 

A second steady-state method involves the analysis of the broadening of the nuclear magnetic resonance spectra of phospholipids in bilayers containing low concentrations of spin-labeled phospholipids. A theoretical analysis of the relation between this line broadening and diffusion rates has been given by Brulet and McConnell.3 [In this paper (6) is not correct the subsequent equations are nonetheless correct. For an alternative derivation, see Brulet.2] In this paper it is shown that a number of measurements of nuclear relaxation rates T71 of nuclei in phospholipids are consistent with lateral diffusion constants in the range 10 7 to 10 R cm2/s. 

Some of the methods for measuring molecular diffusion coefficients, together with a few recent references, are (a) diaphragm cell [60,61] (b) boundary layer interferometry [59] (c) shearing plate interferometry [58] (d) chromatographic peak broadening [60] (e) nuclear magnetic resonance and electron spin resonance [62, 63] (f) electrolyte conductance [64] (g) isotopic tracers [65] and (h) laminar jets [66]. 

Comparisons of estimated diffusivity values on zeolites from sorption uptake measurements and those obtained from direct measurements by nuclear magnetic resonance field gradient techniques have indicated large discrepancies between the two for many systems [10]. In addition, the former method has often resulted in an adsorbate diffusivity directly proportional to the adsorbent crystal size [11]. This led some researchers to believe that the resistance to mass transfer may be confined in a skin at the surface of the adsorbent crystal or pellet (surface barrier) [10,11]. The isothermal surface barrier model, however, failed to describe experimental uptake data quantitatively [10,12]. 

Abstract We use Nuclear Magnetic Resonance relaxometry (i.e. the frequency variation of the NMR relaxation rates) of quadrupolar nucleus ( Na) and H Pulsed Gradient Spin Echo NMR to determine the mobility of the counterions and the water molecules within aqueous dispersions of clays. The local ordering of isotropic dilute clay dispersions is investigated by NMR relaxometry. In contrast, the NMR spectra of the quadrupolar nucleus and the anisotropy of the water self-diffusion tensor clearly exhibit the occurrence of nematic ordering in dense aqueous dispersions. Multi-scale numerical models exploiting molecular orbital quantum calculations, Grand Canonical Monte Carlo simulations, Molecular and Brownian Dynamics are used to interpret the measured water mobility and the ionic quadrupolar relaxation measurements. 

A more sophisticated method which has found wide application in the study of intracrystalline diffusion in zeolites is the nuclear magnetic resonance (NMR) pulsed field gradient self-diffusion method. The method, which is limited to hydrocarbons and other sorbates with a sufficient density of unpaired nuclear spins, depends on measuring directly the mean square distance traveled by molecules,... 

The existence of dynamical inhomogeneity also explains certain measurements for self-diffusion in ILs that have previously been attributed to ion pairing. Watanabe and co-workers [165-170] conducted studies on a range of ILs, comparing the molar conductivities calculated via PGSE-NMR (nuclear magnetic resonance) measurement against those obtained via electrochemical... 

The formation of complex ions is an important problem for the study of the structure and properties of molten salts. Several physicochemical measurements give evidence of the presence of complex ions in melts. The most direct methods are the spectroscopic methods which obtain absorption, vibration and nuclear magnetic resonance spectra. Also, the formation of complex ions can be demonstrated, without establishing the quantitative formula of the complexes, by the variation of various physicochemical properties with the composition. These properties are electrical conductivity, viscosity, molecular refraction, diffusion and thermodynamic properties like molar volume, compressibility, heat of mixing, thermodynamic activity, surface tension. 

Measurements of diffusion of neutral solitons have been made using the electron spin resonance (ESR) and the nuclear magnetic resonance (NMR). An unambiguous interpre-... 

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