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TitleEffect of paramagnetic relaxation reagent concentration on the nuclear overhauser enhancement and on the use of gated proton decoupling in quantitative carbon-13 nuclear magnetic resonance spectroscopy
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorOzubko, R S
SourceCanada Centre for Mineral and Energy Technology, Energy Research Program, Energy Research Laboratories, Report 78-52 (J), 1978, 25 pages, Open Access logo Open Access
PublisherEnergy, Mines and Resources Canada
Mediapaper; on-line; digital
File formatpdf
SubjectsScience and Technology; geochemistry; nuclear applications; carbon isotopes; spectroscopy; paramagnetic minerals
Illustrationsschematic models; plots
Released1978 05 01; 2021 07 20
AbstractTo determine the effect of the concentration of the paramagnetic relaxation reagent chromium (tris)acetylacetonate [Cr(acac)3] when used in quantitative carbon-13 nuclear magnetic resonance spectroscopy (13C NMR), the spectrum of pyrene, a compound with extreme values of spin lattice relaxation times (T1) and nuclear Overhauser enhancements (NOE), was studied. The NOE, line broadening and shifting of the five pyrene resonances were determined for up to 0.3 M Cr(acac)3. The quaternary and protonated carbons displayed different NOE's until all were completely quenched with the Cr(acac)3 greater than 0.25 M. Employing this Cr(acac)3 concentration in quantitative NMR analyses eliminated errors due to differing NOE's, but led to considerable line broadening and shifting. The use of lower Cr(acac)3 concentrations in these analyses, such as the commonly reported 0.05 - 0.15 M, necessitates the joint use of gated proton decoupling to eliminate the NOE differences which still exist at these concentrations.

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