Gas chromatography–mass spectrometry Analysis Types of ionization Electron ionization
This is like the filament one would find in a standard incandescent light bulb. The electrons hit the molecules, causing the molecule to fragment in a characteristic way that can be repeated. EI has few, if any, fragments having a mass that is near the mass of the original molecule. Chemists consider hard ionization to be shooting electrons into the sample molecules. The use of 70 eV helps to compare the spectra generated from the test sample against known library spectra. The software searches the library spectra using a matching algorithm such as Probability Based Matching or dot-product matching. Many method standardization agencies now control these algorithms and methods to assure their objectivity.