For the positional isotopic analysis of tritium-labelled organic compounds which are isolated at the end of a tracer experiment,
it is proposed to render high-resolution triton-NMR spectroscopy sufficiently sensitive as follows. Andrew's rotating magnetic
field is used to narrow the NMR lines that are detected by observing the anisotropy of the β-radiation of the sample which
is kept at 0.01 °K by a helium-dilution refrigerator. In this context, the usefulness of the rotating magnetic field for cryogenic
proton-NMR spectroscopy is pointed out.