Editing Ion source (section)

===Atmospheric-pressure chemical ionization===
{{Main|Atmospheric-pressure chemical ionization}}
Atmospheric-pressure chemical ionization uses a solvent spray at atmospheric pressure.<ref name="pmid17405144">{{cite journal |vauthors=Prakash C, Shaffer CL, Nedderman A |title=Analytical strategies for identifying drug metabolites |journal=Mass Spectrometry Reviews |volume=26 |issue=3 |pages=340–69 |date=2007 |pmid=17405144 |doi=10.1002/mas.20128|bibcode = 2007MSRv...26..340P }}</ref> A spray of solvent is heated to relatively high temperatures (above 400 degrees Celsius), sprayed with high flow rates of nitrogen and the entire aerosol cloud is subjected to a [[corona discharge]] that creates ions with the evaporated solvent acting as the chemical ionization reagent gas. APCI is not as "soft" (low fragmentation) an ionization technique as ESI.<ref name="pmid16723751">{{cite journal |vauthors=Zaikin VG, Halket JM |title=Derivatization in mass spectrometry--8. Soft ionization mass spectrometry of small molecules |journal=European Journal of Mass Spectrometry |volume=12 |issue=2 |pages=79–115 |date=2006 |pmid=16723751 |doi=10.1255/ejms.798|s2cid=34838846 }}</ref> Note that atmospheric pressure ionization (API) should not be used as a synonym for APCI.<ref>{{Cite book|date=2009|doi=10.1351/goldbook.A00492|chapter=Atmospheric pressure ionization in mass spectrometry|title = IUPAC Compendium of Chemical Terminology|isbn = 978-0-9678550-9-7}}</ref>