High-Field MAS NMR of
Strontium-87 in Environmental Samples
EMSL Project ID
10293
Abstract
Our proposal is to use ultra-high-field MAS NMR spectroscopy to study strontium nuclei in solid samples. Strontium is a quadrupolar nucleus (I = 9/2) with a very low gyromagnetic ratio, large quadrupolar coupling constant, and low receptivity. The breadth of the resonances (on the order of 50-200 kHz) makes successful MAS NMR experiments difficult; indeed, it has been questioned in a recent publication as to whether MAS at moderate speeds is suitable for strontium nuclei in any system. MAS of solid materials is advantageous in that it removes the effects of chemical shift anisotropy from the spectrum and improves the sensitivity of the measurement. MAS forces all the intensity of a resonance into main peaks and spinning sidebands separated by an integer multiple of the rotational frequency. Through preliminary investigations with a spinning rate of 9 kHz in an 11.74 T magnet, we have resolved two crystallographically inequivalent strontium sites in strontium carbonate, though the primary peaks are poorly resolved. The benefits of high-fields for studying quadrupolar nuclei, such as improved sensitivity and a quadrupolar contribution to line-width that scales inversely with applied field strength, make MAS experiments at the fastest possible spin rate in the highest available field an excellent opportunity to improve sensitivity and resolution of strontium NMR experiments in solid samples. To our knowledge, no publications to date contain MAS NMR spectra of strontium nuclei. In this research we propose the use of MAS NMR at the highest available field strength to observe strontium in ionic salts, zeolites, and clay minerals in order to improve sensitivity and demonstrate that MAS NMR of strontium can be effective at resolving multiple resonances. We would also like to use MAS NMR to study binding sites selective for strontium in clay minerals and zeolites representative of those in contaminated soils at the Hanford site. This research should generate a number of peer-reviewed publications.
Project Details
Project type
Capability Research
Start Date
2005-01-14
End Date
2005-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
NMR Studies of Heat-Induced Transitions in Structure and Cation Binding Environments of a Strontium-Saturated Swelling Mica Appl. Mag. Reson. (2007) 32, 595-612 DOI 10-1007/s00723-007-0042-z Printed in the Netherlands