There is provided a mass spectrometric based method for sample
identification, including the steps of introducing sample compounds into
a vacuum chamber of a mass spectrometer in a seeded supersonic molecular
beam, ionizing with electrons the sample compounds, being vibrationally
cold molecules, in the supersonic molecular beam during their flight
through an electron ionization ion source, mass analyzing the ionized
sample compounds with a mass analyzer of a mass spectrometer to obtain a
mass spectrum of at least one compound in the sample, identifying the
molecular ion group of isotopomers in the mass spectrum, generating
various molecular elemental formulas from the identified molecular ion
and a pre-allocated list of elements, reducing the number of the
molecular elemental formulas by the incorporation of chemical valence
considerations and constraints, calculating isotope abundances for the
generated elemental formulas, comparing the calculated isotope abundances
with the experimentally obtained mass spectral isotope abundance, and
listing the generated elemental formulas according to their degree of
matching to the experimentally obtained mass spectral isotope abundance.