Liquid-state NMR and scalar couplings in microtesla magnetic fields.
We obtained nuclear magnetic resonance (NMR) spectra of liquids in fields of a few microtesla, using prepolarization in fields of a few millitesla and detection with a dc superconducting quantum interference device (SQUID). Because the sensitivity of the SQUID is frequency independent, we enhanced both signal-to-noise ratio and spectral resolution by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. In the absence of chemical shifts, proton-phosphorous scalar (J) couplings have been detected, indicating the presence of specific covalent bonds. This observation opens the possibility for "pure J spectroscopy" as a diagnostic tool for the detection of molecules in low magnetic fields.
McDermott
Robert
R
Department of Physics, University of California, Berkeley, CA 94720, USA. rmcderm@socrates.berkeley.edu
Trabesinger
Andreas H
AH
Muck
Michael
M
Hahn
Erwin L
EL
Pines
Alexander
A
Clarke
John
J
D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods*; D008280:Magnetics; D008899:Mineral Oil / Q000737:chemistry; D010756:Phosphoric Acids / Q000737:chemistry
D010756:Phosphoric Acids; D008899:Mineral Oil; C030242:phosphoric acid