A new mass spectrometric method for determining the degree of labeling with heavy isotopes: The study of deuterated toluenes

A new method of general applicability for determining the percentage deuterium labeling in organic compounds is described. It uses the heights of ‘metastable peaks’ in the mass spectrum to determine the relative amounts of deuterated and undeuterated species. The method is illustrated by describing the analysis of mixtures of toluene-o-d₁ and toluene, of toluene α-d₁ and toluene, and of toluene-2,6-d₂, toluene-o-d₁ and toluene.