PMID- 21875027
OWN - NLM
STAT- MEDLINE
DCOM- 20120206
LR  - 20121115
IS  - 1520-5851 (Electronic)
IS  - 0013-936X (Linking)
VI  - 45
IP  - 20
DP  - 2011 Oct 15
TI  - Paramagnetic relaxation enhancement (PRE) as a tool for probing diffusion in 
      environmentally relevant porous media.
PG  - 8866-72
LID - 10.1021/es2010946 [doi]
AB  - The transport diffusivity of the paramagnetic molecule 
      2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was measured by monitoring its 
      influence on the NMR transverse relaxation time (T(2)) on surrounding water protons 
      - also known as paramagnetic relaxation enhancement (PRE). Due to the nature of 
      the PRE effect, few paramagnetic molecules are able to simultaneously reduce the 
      T(2) of many NMR active nuclei, which represents a significant gain in sensitivity. 
      In an aqueous solution, the minimal detectable TEMPO concentration was around 70 
      ppm. The value of the diffusivity was estimated by fitting the relaxation data, 
      collected as a function of time, with the appropriate solutions of the second 
      Fick's law in respect to the corresponding sample geometry and dimensions. 
      Considering the experimentally determined TEMPO relaxivity in water ("TEMPO-water 
      relaxivity"; R(TEMPO) = (1.05 +/- 0.12) x 10(-)(3) ppm(-)(1) s(-)(1)), the obtained diffusion 
      coefficients (D) of TEMPO in homogeneous solution and in a water saturated sand 
      column (D(bulk) = (6.7 +/- 0.4) x 10(-)(1)(0) m(2) s(-)(1) and D(sand) = (1.4 +/- 0.5) x 10(-)(1)(0) m(2) 
      s(-)(1), respectively) are in good agreement with the expected values (literature 
      values: D(bulk) = 6.6 x 10(-)(1)(0) m(2) s(-)(1), 1.3 x 10(-)(1)(0) m(2) s(-)(1) < D(sand) < 2.3 x 10(-)(1)(0) 
      m(2) s(-)(1)). This new approach enables one to determine the diffusivity of 
      paramagnetic molecules in homogeneous (aqueous solution) and porous media with 
      basic NMR equipment, at low concentrations and in a noninvasive manner.
FAU - Furtado, Filipe
AU  - Furtado F
AD  - Department of Environmental Engineering, Helmholtz Centre for Environmental 
      Research-UFZ, Leipzig, Germany.
FAU - Galvosas, Petrik
AU  - Galvosas P
FAU - Stallmach, Frank
AU  - Stallmach F
FAU - Roland, Ulf
AU  - Roland U
FAU - Karger, Jorg
AU  - Karger J
FAU - Kopinke, Frank-Dieter
AU  - Kopinke FD
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20110916
PL  - United States
TA  - Environ Sci Technol
JT  - Environmental science & technology
JID - 0213155
RN  - 0 (Cyclic N-Oxides)
RN  - VQN7359ICQ (TEMPO)
SB  - IM
MH  - Cyclic N-Oxides/*chemistry
MH  - Diffusion
MH  - Magnetic Resonance Spectroscopy/*methods
MH  - Porosity
EDAT- 2011/08/31 06:00
MHDA- 2012/02/07 06:00
CRDT- 2011/08/31 06:00
PHST- 2011/08/31 06:00 [entrez]
PHST- 2011/08/31 06:00 [pubmed]
PHST- 2012/02/07 06:00 [medline]
AID - 10.1021/es2010946 [doi]
PST - ppublish
SO  - Environ Sci Technol. 2011 Oct 15;45(20):8866-72. doi: 10.1021/es2010946. Epub 
      2011 Sep 16.