Gaseous mixtures of hydrogen and deuterium from 85 to 100 percent deuterium have been rapidly analyzed spectroscopically to within 0.1 percent of the major component. A 150-megacycle electrodeless discharge in flowing gas has been used. Under typical conditions the value of the measured intensity ratio was found to vary with pressure in an unexplained manner. The addition of air up to 2.5 percent has not affected the measured isotope ratio.
HERBERT P. BROIDA and JAMES W. MOYER, "Spectroscopic Analysis of Deuterium in Hydrogen-Deuterium Mixtures," J. Opt. Soc. Am. 42, 37-41 (1952)