The Mass spectrum of any substance is the distribution of matter according to atomic and molecular masses that can be found when a sample of the substance is tested. This distribution is usually found using a mass spectrometer which breaks the substance into ionized fragments (atoms or molecules) which are measured for their mass and relative population. The mass spectrometer produces a graphic depicting the relative intensity (or quantity) versus the mass-to-charge ratio (m/e) of the various constituents of the sample.