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Small discrepancies between 3H and 1H chemical shifts in organic compounds led to the finding that the ratio of Larmor frequencies ωT/ωH depends on the carbon‐hydrogen bond hybridisation. The ‘best’ ratio for ghost referencing of 3H NMR spectra was then determined from measurements on purified partially tritiated TMS as 1.066639738±2 × 10−9. Some 3H isotope effects on chemical shifts are listed and the 3H isotope effect on the methylene geminal coupling constant in benzyl methyl sulphoxide is measured. Use of 2H in the measurement of 2J(HH) coupling constants has inherent disadvantages, overcome by use of 3H substitution.

Hydrogen bonding within the structures of three Schiff bases (1-3), obtained by condensation of 4-methoxy-, 5-methoxy- and 4,6-dimethoxysalicylaldehyde with methylamine, was investigated by measuring deuterium and tritium NMR isotope effects. The primary deuterium and tritium isotope effects (delta(XH)-delta(XD/T)) and secondary one-bond nitrogen deuterium effect appear to be very useful parameters for defining the character of intramolecular hydrogen bonds. The tritium isotope effects were also determined for nitrogen-hydrogen one-bond coupling constants for both 4-methoxy and 4,6-dimethoxy derivatives. These parameters are seen to be highly sensitive to hydrogen bond characteristics and can be used to distinguish localized and tautomeric hydrogen bonds.

A series of 50 neurochemicals, important for the investigation of neurotransmission processes, has been labelled with tritium, using in all 8 methods. Tritium nuclear magnetic resonance spectroscopy has been employed to determine the positions and extent of labelling in these neurochemicals which can be important for their use in tracer studies. The specificity of the labelling processes is discussed.