Mass spectra are obtained by measuring the itensities while the mass is passing through a selected range. The figure shows a mass spectrum of NBS steel standard 449. The elements V, Cu, Nb, Mo, Ta, and W at concentrations far below one percent of weight are clearly identified.
High resolved mass spectra are important for the distinction of the mass of interest from closely neighbouring masses. The figure shows the separation of the mass 56Fe from the neighbours 28Si2 and 27Al29Si.