Polarization transfer by selective homonuclear technique for suppression of uncoupled spins in NMR spectroscopy

摘要

A method for suppressing at least one undesired resonance response signal while facilitating reception of at least one other desired NMR response signal from a coupled spin resonance in NMR spectroscopy, utilizes a pair of alternating sequences of RF signal pulses, with each sequence having an initial π/2 RF pulse, followed by a π RF signal pulse having a temporal midpoint at a time interval T after the temporal midpoint of the initial pulse (where T=n/4J, with n being an odd integer and J being the spin coupling constant of the hydrogen nuclei) and a final π RF signal pulse with a temporal midpoint at twice the time interval T after the temporal midpoint of the first π RF signal pulse in that sequence. Only one of the pair of sequences is provided with a polarization transfer narrow-band π RF signal pulse symmetrically disposed about a temporal midpoint located at substantially a time interval T after the first π RF signal pulse of that sequence and substantially at a frequency removed from the resonance frequency of at least one undesired uncoupled spin resonance. Response signals are acquired within a gating period including a temporal point thereof occurring at a time interval T afterthe temporal midpoint of the final π RF signal pulse. The pair of recovered sets of data are subtracted from one another to obtain a final data set In which noncoupled spin resonance data is substantially cancelled but desired coupled spin resonance data is preserved.