title: Enhanced (13)C PFG NMR for the study of hydrodynamic dispersion in porous media.
abstract: PFG NMR methods are frequently used as a means of probing both coherent and incoherent molecular motions of fluids contained within heterogeneous porous media. The time scale over which molecular displacements can be probed in a conventional PFG NMR experiment is limited by the relaxation characteristics of (1)H - the nucleus that is typically observed. In multiphase systems, due to its sensitivity to susceptibility gradients and interactions with surfaces,(1)H signal is frequently characterized by rapid T(1) and T(2) relaxation. In this work, a heteronuclear approach to PFG NMR is demonstrated which allows the study of molecular displacement over extended time scales (and, consequently, length scales) by exploiting the longer relaxation time of (13)C. The method presented employs the DEPT technique of polarization transfer in order to enhance both the sensitivity and efficiency of (13)C detection. This hybrid coherence transfer PFG technique has been used to acquire displacement propagators for flow through a bead pack with an observation time of up to 35 s.
authors.affiliation: Magnetic Resonance Research Centre, Department of Chemical Engineering, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK.
authors.forename: Belinda S
authors.initials: BS
authors.lastname: Akpa
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Holland
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Sederman
authors.forename: Michael L
authors.initials: ML
authors.lastname: Johns
authors.forename: Lynn F
authors.initials: LF
authors.lastname: Gladden
mesh_terms: D002247:Carbon Isotopes / Q000737:chemistry*; D003102:Colloids / Q000737:chemistry*; D045424:Complex Mixtures / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D016062:Porosity; D012815:Signal Processing, Computer-Assisted; D014867:Water / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D003102:Colloids; D045424:Complex Mixtures; D014867:Water