Heteronuclear relayed coherence transfer. The selective observation of protons in spin systems containing heteronuclei

A pulse sequence for heteronuclear relayed coherence transfer (RCT) X → H → H is described and used to selectively observe the protons of a spin system which contains a heteronucleus. A two-dimensional extension of the sequence permits the protons of spin systems containing heteronuclei to be separated by virtue of the chemical shift of the heteronucleus. Performing the relay from the heteronucleus to the proton spin system is preferable to the conventional heteronuclear RCT sequence (H → H → X) since the ultimate detection of proton rather than heteronuclear magnetization affords an increase in the sensitivity of the experiment.