Final answer:
The most likely substance corresponding to an unlabeled peak on a gas chromatograph, given the analyte is enriched with heavy isotopes of hydrogen, is tritium (³H), as it has the greatest mass among the hydrogen isotopes.
Step-by-step explanation:
Analyzing a gas chromatograph with an unlabeled peak, where the analyte is enriched with heavy isotopes of hydrogen, the most likely corresponding substance is tritium.
Among the isotopes of hydrogen, such as protium, deuterium, and tritium, tritium is the heaviest with one proton and two neutrons in its nucleus (³H).
Protium (¹H) has no neutrons, deuterium (²H or 'D') has one neutron, and tritium (³H or 'T') has two neutrons, making tritium the isotope with the greatest mass.
If the analyte is enriched with heavy isotopes of hydrogen and given that deuterium and tritium have lower vapor pressure than protium, tritium would be the most enriched in the sample, leading to a higher likelihood of detecting it on a chromatograph.