page_title: Chemical ionization
section_title: Applications
hierarchical_section_title: Chemical ionization / Applications
caption_attribution_description: English: PAN CIMS (peroxynitrate chemical ionization mass spectrometer)
context_page_description: Chemical ionization is a soft ionization technique used in mass spectrometry. This was first introduced by Burnaby Munson and Frank H. Field in 1966. This technique is a branch of gaseous ion-molecule chemistry. Reagent gas molecules are ionized by electron ionization, which subsequently react with analyte molecules in the gas phase in order to achieve ionization. Negative chemical ionization, charge-exchange chemical ionization and atmospheric-pressure chemical ionization are some of the common variations of this technique. CI has several important applications in identification, structure elucidation and quantitation of organic compounds. Beside the applications in analytical chemistry, the usefulness in chemical ionization extends toward biochemical, biological and medicinal fields as well.
context_section_description: CI mass spectrometry is a useful tool in structure elucidation of organic compounds. This is possible with CI, because formation of [M+1]⁺ eliminates a stable molecule, which can be used to guess the functional groups present. Besides that, CI facilitates the ability to detect the molecular ion peak, due to less extensive fragmentation. Chemical ionization can also be used to identify and quantify an analyte present in a sample, by coupling chromatographic separation techniques to CI such as gas chromatography (GC), high performance liquid chromatography (HPLC) and capillary electrophoresis (CE).  This allows selective ionization of an analyte from a mixture of compounds, where accurate and precised results can be obtained.
caption: Peroxynitrate chemical ionization mass spectrometer at the US National Oceanic and Atmospheric Administration
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