Term: chemical ionization
https://doi.org/10.1351/goldbook.C01026

Definition:
This concerns the process whereby new ionization species are formed when gaseous molecules interact with ions. The process may involve transfer of an electron, proton or other charged species between the reactants. When a positive ion results from chemical ionization, the term may be used without qualification. When a negative ion is involved, the term negative ion chemical ionization should be used; note that negative ion formation by attachment of a free electron does not fall within this definition. Chemical ionization and chemi-ionization are two terms which should not be used interchangeably.

Related Terms:
1) chemi-ionization (<em>in mass spectrometry</em>) (http://doi.org/10.1351/goldbook.C01044).
2) ionization (<em>in mass spectrometry</em>) (http://doi.org/10.1351/goldbook.I03183).
3) proton (<em>in mass spectrometry</em>) (http://doi.org/10.1351/goldbook.P04906).
4) attachment (<em>in mass spectrometry</em>) (http://doi.org/10.1351/goldbook.A00512).
5) electron attachment (<em>in mass spectrometry</em>) (http://doi.org/10.1351/goldbook.E01979).

Source: Orange Book, 2nd ed., p. 204 (https://media.iupac.org/publications/analytical_compendium/)

Citation: 'chemical ionization' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.C01026

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