A mixture of compounds to be analysed is initially injected into the GC where the mixture is vaporized in a heated chamber. The gas mixture travels through a GC column, where the compounds become separated as they interact with the column. The chromatogram on the right shows peaks which result from this separation. Those separated compounds then immediately enter the mass spectrometer. Below is a general schematic of a mass spectrometer.
All mass spectrometers consist of three distinct regions.
An electron which strikes a molecule may impart enough energy to remove another electron from that molecule. EI Ionization usually produces singly charged ions containing one unpaired electron. A charged molecule which remains intact is called the molecular ion. The methanol ion may fragment in various ways, with one fragment carrying the charge and one fragment remaining uncharged. Therefore an ion's path will depend on its mass.