Magnetic resonance, pulsed gradient spin

J. D. Seymour, B. Manz, P. T. Callaghan 1999, (Pulsed gradient spin echo nuclear magnetic resonance measurements of... 

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. 

An a priori prediction for cocrystal formation has been reported that is based on intermolecular pair interactions that have been characterized using pulsed gradient spin-echo nuclear magnetic resonance, and tested against the conventional ionization constant guideline for 25 molecular pairs [17]. This approach was shown to work well even in different... 

Callaghan, P. T., Coy, A., Halpin, T. P. J., MacGowan, D., Packer, K. J., and Zelaya, F. O. (1992). Diffusion in porous systems and the influence of pore morphology in pulsed gradient spin-echo nuclear magnetic resonance studies. J. Chem. Phys. 97, 651-662. 

Basically two nuclear magnetic resonance (NMR) techniques can be used to determine the partition coefficient. The first is based on the Fourier transform NMR pulsed-gradient spin echo (FT-PGSE) self-diffusion techiuque, the other by the NMR paramagnetic relaxation technique. In both techniques the fraction of solute in the micelle, a, is determined and can thus be calculated through Equation 6.10. 

Geetha, B. Mandal, A. B. Self-Diffusion Studies on Methoxy Polyethyleneglycol Macromonomer Micelles By Using Cyclic Voltammetric and Fourier Transform Pulsed Gradient Spin Echo Nuclear Magnetic Resonance Techniques. Langmuir, 1995,11,1464-1467. 

Chung, S.H., Bajue, S., and Greenbaum, S.G. (2000) Mass transport of phosphoric acid in water a and P pulsed gradient spin-echo nuclear magnetic resonance study. /. Chem. Phys., 112 (19), 8515-8521. 

The microstructure of complex fluids such as ILs, surfactant systems, and liquid crystals can be profitably investigated by means of pulsed gradient spin-echo nuclear magnetic resonance (PGSE-NMR) experiments, a technique that allows the determination of the self-diffusion coefficients. 

Stilbs, P. 1987. Fourier transform pulsed-gradient spin-echo studies of molecular diffusion. Progress in Nuclear Magnetic Resonance Spectroscopy, 19(1), 1-45. 

The different mobilities of monomers versus micelles can be used as a means to determine the value of CMC. The self-diffusion coefficients of the water and surfactant can be measured by pulsed-gradient spin Fourier-transform nuclear magnetic resonance echo (FT-NMR) spectroscopy, following the NMR spectra (13). Hence, a plot of the diffusion coefficient D versus the surfactant concentration shows a change in slope corresponding to the CMC. 

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