A mass spectrum that today is rarely seen.

The mass spectrum of a mixture of H2, He, and N2 with a peak at every mass between m/z 1 and 8 (except for m/z 6) is presented as an example of the richness of information that can exist in this region that is rarely examined in biomedical mass spectrometry. The particular point of the experiment that generated this spectrum was to evaluate a chemical reaction interface mass spectrometric (CRIMS) procedure to measure H/D ratios in labeled analytes. The persistence of an ion-molecule reaction that generates H3+ interferes with the detection of HD+. Observing a second ion-molecule product of hydrogen at m/z 5 leads to a different approach to correcting the signal at m/z 3 than extrapolating the m/z 3/2 ratio to zero hydrogen.