Pulsed fields gradient spin-echo NMR

Umecky, T, Kanakubo, M., and Ikushima, Y., Self-diffusion coefficients of l-butyl-3-methylimidazolium hexafluorophosphate with pulsed-field gradient spin-echo NMR technique. Fluid Phase Equilib., 228-229, 329, 2005. 

Toonkool, P., Regan, D. G., Kuchel, P. W., Morris, M. B., and Weiss, A. S. (2001a). Thermodynamic and hydrodynamic properties of human tropoelastin. Analytical ultracentrifuge and pulsed field-gradient spin-echo NMR studies. / Biol. Chem. 276, 28042-28050. 

Gao, P. and Fagerness, P., Diffusion in HPMC gels. I. Determination of drug and water diffusivity by pulsed-field-gradient spin-echo NMR, Pharmaceutical Research, Vol. 12, No. 7, 1995, pp. 955-964. 

Using pulsed field gradient spin echo NMR, Guering and Lindman [14] and, independently, Clarkson et al. [15] measured the self-diffusion coefficients of the components of microemulsions of sodium dodecyl sulfate (SDS), toluene, butanol, and NaCl brine. The results (Fig. 8) establish unequivocally the existence of bicontinous microemulsion. 

Other indications about the intramolecular reaction were concluded from pulsed field gradient spin echo-NMR (PGSE-NMR) measurements [60]. This method gives informations about the incorporation of the substrate into the micelle and enabled the measurement of an average diffusion coefficient of the catalyst below and above the CMC. 

Molecular self-diffusion coefficients are experimentally easily accessible and can be measured accurately with various techniques. However, the Fourier transform pulsed field gradient spin-echo NMR (FT PGSE NMR) approach has during the last decade proved to be superior to other approaches for several reasons. In this technique the displacement of nuclear spins in a controlled magnetic field gradient is monitored, and the contributions of different components are resolved by Fourier transformation of the NMR signal (spin echo). 

Recently, data regarding the lignin study both in the solid state and solution with the modem and performance techniques, namely the small-angle X-ray scattering (SAXS) and ultra-smaU-angle X-ray scattering (USAXS) [166], pulsed field gradient spin-echo NMR [167, 168], nano zeta sizer techniques [169] have been reported. 

As a qualitative means to investigate the ionic nature of acid-base systems, various techniques have been employed such as one- or two-dimensional nuclear magnetic resonance (NMR) spectroscopy [31], infrared (IR) spectroscopy [32], the Walden plot [33], the ratio of molar conductivities AjmpMNMR (determined by electrochemical impedance spectroscopy and pulse-field-gradient spin-echo NMR, respectively) [34], Some of these will be discussed below. 

Pulsed field gradient spin echo NMR is generally the method of choice for diffusion measurements on liquid samples (see Section 5.1 in this chapter). With modem high field instruments, however, severe problems can arise when it is applied to samples with very high proton concentrations because of the presence of radiation damping. Connel et al reduced the problems by a suitable choice of experimental parameters, in particular the use of modified stimulated echo pulse sequences with a reduced flip angle for the first pulse. 

Pulsed-Field Gradient Spin-Echo NMR Diffusion NMR experiments resolve different compounds in a mixture based on their diffusion coefficients, depending on physical parameters such as size and shape of the molecules, temperature, and viscosity. The diffusion NMR technique is often referred to as diffusion-ordered spectroscopy (DOSY) or pulsed-field gradient spin-echo (PGSE) NMR. A series of NMR diffusion spectra are acquired as a function of the gradient strength G (Fig. 2.19) [56], and the slope of the peak decay is used to obtain the diffusion coefficient D. Furthermore, the hydrodynamic radius can be obtained from the Stokes-Einstein equation (Eq. 2.3). 

Diffusion Coefficients of l-Butyl-3-methylimidazolium Hexafluorophosphate with Pulsed-Field Gradient Spin-Echo NMR Technique. 

In this study we have investigated the structural and interaction parameters of ternary water/octane/CiaEs system by means of SAXS. Phase behavior of this system was studied by Kahlweit et al. [9]. This system shows interesting phase behavior (Fig. 1). One can study the structures of low-temperature microemulsion (LTM) phase, middle-temperature lamellar (MTL) phase and high-temperature microemulsion (HTM) phase by changing temperature only, provided that the sample contains approximately more than 12 wt% of surfactant at equal volume fraction of water and oil. Bodet et al. have clarified the structural evolution of this system by means of pulsed-field gradient spin-echo NMR, quasi-elastic light scattering and freeze-fracture transmission electron microscopy [10]. Local structure of the bilayer and monolayer of the same system was also studied by Strey et al. [11]. Recently, we have studied the mechanism of the phase transition [12]. 

Limitations on neutron beam time mean that only selected surfactants can be investigated by OFC-NR. However, parametric and molecular structure studies have been possible with the laboratory-based method maximum bubble pressure tensiometry (MBP). This method has been shown to be reliable for C > 1 mM.2 Details of the data analysis methods and limitations of this approach have been covered in the literature. Briefly, the monomer diffusion coefficient below the cmc, D, can be measured independently by pulsed-field gradient spin-echo NMR measurements. Next, y(t) is determined by MBP and converted to F(0 with the aid of an equilibrium equation of state determined from a combination of equilibrium surface tensiometry and neutron reflection. The values of r(f) are then fitted to a diffusion-controlled adsorption model with an effective diffusion coefficient which is sensitive to the dominant adsorption mechanism 1 for... 

S. V. Dvinskikh, I. Furo, H. Zrmmermann, and A. Maliniak, Anisotropic self-diffusion in thermotropic liquid crystals studied by H and pulsed-field-gradient spin-echo NMR, Phys. Rev. E 65, 061701-1/9 (2002). 

C PULSED FIELD GRADIENT SPIN ECHO NMR METHOD APPLIED TO NEMATIC LIQUID CRYSTALS... 

Ciszkowska M, Zeng L, Stejskal EO, Osteryoung JG (1995) Transport of thallium (I) counterion in polyelectrolyte solution determined by voltammetry with microelectrodes and by pulsed-field-gradient, spin-echo NMR. J Phys Chem 99 11764-11769... 

In this article, we have discussed the use of ionic liquids as solvent for the seE-assembly of surfactants. In ionic liquids, the formation of the same types of amphiphile self-assembly phases as aqueous systems (micelles, vesicles and microemulsions) was evidenced. These aggregates were characterized by surface tension measurements, differential scanning calorimetry, scattering experiments (DLS and SANS), pulse field gradient spin-echo NMR, electrical conductivity measurements, electron microscopy. 

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