Probing Liquid-Liquid Interfaces with Spatially Resolved NMR Spectroscopy

Department of Material Analysis, ISAS, Dortmund, Germany.
Angewandte Chemie International Edition (Impact Factor: 11.34). 08/2009; 48(34):6343-5. DOI: 10.1002/anie.200901389
Source: PubMed


Available from: Joerg Lambert, May 21, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The use of susceptibility matching to minimize spectral distortion of biphasic samples layered in a standard 5 mm NMR tube is described. The approach uses magic angle spinning (MAS) to first extract chemical shift differences by suppressing bulk magnetization. Then, using biphasic coaxial samples, magnetic susceptibilities are matched by titration with a paramagnetic salt. The matched phases are then layered in a standard NMR tube where they can be shimmed and examined. Linewidths of two distinct spectral lines, selected to characterize homogeneity in each phase, are simultaneously optimized. Two-dimensional distortion-free, slice-resolved spectra of an octanol/water system illustrate the method. These data are obtained using a 2D stepped-gradient pulse sequence devised for this application. Advantages of this sequence over slice-selective methods are that acquisition efficiency is increased and processing requires only conventional software.
    Journal of Magnetic Resonance 03/2012; 218:147-52. DOI:10.1016/j.jmr.2012.02.012 · 2.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In our paper, we study the interface wettability, diffusivity and molecular orientation between crude oil and different fluids for applications in Improved Oil Recovery (IOR) processes through atomistic Molecular Dynamics (MD). The salt concentration, temperature and pressure effects on the physical chemistry properties of different interfaces between IOR agents [brine (H2O+%NaCl), CO2, N2 and CH4] and crude oil have been determined. From the interfacial density profiles, an accumulation of aromatic molecules near the interface has been observed. In the case of brine interfaced with crude oil, our calculations indicate an increasing in the interfacial tension with increasing pressure and salt concentration, which favors oil displacement. On the other hand, the other fluids studied (CO2, N2 and CH4) the interfacial tension decreases with increasing pressure and temperature. With interfacial tension reduction, an increase in fluid diffusivity in the oil phase is observed. We also studied the molecular orientation properties of the hydrocarbon and fluids molecules in the interface region. We perceived that the molecular orientation could be affected by changes in the interfacial tension and diffusivity of the molecules in the interface region with the increased pressure and temperature: pressure (increasing) → interfacial tension (decreasing) → diffusion (increasing) → molecular ordering. From the molecular point of view, the combination of low interfacial tension and high diffusion of molecules in the oil phase, gives the CO2 molecules unique properties as an IOR fluid compared with other fluids studied here.
    The Journal of Physical Chemistry B 11/2012; 116(50). DOI:10.1021/jp310172j · 3.38 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: It is well-known that the amphiphilic solutes are surface-active and can accumulate at the oil-water interface. Here, we have investigated the water and a light-oil model interface by using molecular dynamic simulations. It was found that aromatics concentrated in the interfacial region, whereas the other hydrocarbons were uniformly distributed throughout the oil phase. Similar to previous studies, such concentrations were not observed at pure aromatics-water interfaces. We show that the self-accumulation of aromatics at the oil-water interface is driven by differences in the interfacial tension, which is lower for aromatics-water than between the others. The weak hydrogen bonding between the aromatic rings and the water protons provides the mechanism for lowering the interfacial tension.
    Journal of the American Chemical Society 12/2010; 132(51):18281-6. DOI:10.1021/ja107519d · 11.44 Impact Factor