In most cases in our laboratory, detection is performed by thermal conductivity. Since isotopes of an atom have the same number of electrons as the atom, this process does not distinguish one isotope of an atom from the other. The illustration below, using Deuterium, will give an example of how the results will appear.
Molecular Formula: C10H10D2O
Molecular Weight: 150.212
%C = 120.1/150.212 = 79.95
%H = 10.08/150.212 = 6.71
%D = 4.032/150.212 = 2.68
%O = 16.00/150.212 = 10.65
Since our instruments detect all D atoms as if they were H, the above illustration would be detected as H12.
H + D as H = 10.08 + 2.016 / 150.212 =8.05
Note: Adding the %’s of H and D together would erroneously yield 9.39%.