See also DART and DESI.Ītmospheric Pressure Ionization (API) - the term used to refer generally to techniques such as electrospray (ESI) and atmospheric pressure chemical ionization (APCI) and others that operate at atmospheric pressure.Ītmospheric Pressure Chemical Ionization (APCI) - originally called solvent-mediated electrospray it is more often successfully applied to neutral molecules that don't ionize easily directly out of solution. Relatively unambiguous identifications can be made of individual compounds from complex mixtures at low levels using accurate mass instruments. The heat volatilizes a surprisingly large number of samples and ions are formed by charge exchange with metastable ions created by the APCI plasma.
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The signal for all ions resulting from the fragmentation of a single analyte or compounds compared to a base peak (the relative abundance of each ion) is used to determine the fit of a fragmented pattern to a library spectrum for positive identification.ĪSAP (atmospheric solids analysis probe) - based on work by Horning in the 1970s this form of sample ionization developed by McEwen and McKay uses a standard APCI plasma but forms ions by placing the sample in a heated nitrogen stream. The following list of terms is derived from common usage throughout the industry as an adjunct to the discussions in this primer and includes terms and techniques no longer in common usage.Ībundance - when viewed as similar to absorbance displayed on a UV detector the vertical increase in signal above background indicates an increased occurrence of that particular ion (when the x axis is calibrated in mass units) or total ions present (when the horizontal axis is calibrated in time or scans).
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