Gases qualitative analysis

The analysis of spectra assumes certain working hypotheses  

Every type of molecule produces a certain, constant mass spectrum or fragment spectrum which is characteristic for this type of molecule (fingerprint, cracking pattern). 

The spectrum of every mixture of gases is the same as would be found 

The ion flow for each peak is proportional to the partial pressure of each component responsible for the peak. Since the ion flow is proportional to the partial pressure, the constant of proportionality (sensitivity) varies from one gas to the next. 

Although these assumptions are not always correct (see Robertson Mass Spectrometry) they do represent a useful working hypothesis. 

---