Often I have peaks in my mass spectra that don?t appear to make sense. How can I tell if a mass spectral peak belongs in a particular spectrum?
Mass spectral sources can come from a lot of sources other than the analyte you are trying to identify (i.e., column bleed, matrix contaminants, instrument contaminants, etc.). The best way to determine if a particular mass spectral peak belongs with any other particular mass spectral peak is plot mass chromatograms for the m/z values of the peaks. If the resulting mass chromatograms rise and fall together with the same general shape, then the mass spectral peaks are from the same source. Often you will see that one mass chromatogram produces a chromatographic peak while the other produces a wavy line offset from zero. This is a good indicator the second m/z value is due to background. Some common GC/MS background ions are observed at m/z 207, 281, 355 (column bleed); m/z 149 due to the electron ionization of esters of phthalic acid that are often used as palletizes; and an ion series with the highest m/z value in each series being 29, 43, 57, and 71 arising from aliphatic hydrocarbons
