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.