Gas chromatography with a modified mordenite column was shown to yield a good hydrogen isotope separation at only 173 K. A linear relationship between peak height and concentration over several orders of magnitude was observed. From an extrapolation of the data it is concluded that all six hydrogen isotopes can be separated in only 13 min. Gas chromatographically separated radioactive hydrogens were detected with a small volume ionization chamber. The detection limit achieved for tritium was found to be about 0.3 ppm.