K.K. Murray, In defense of the quasimolecular ion, J. Mass Spectrom., 56 (2021) e4700; doi: 10.1002/jms.4700.


The term quasimolecular ion has been used to describe ions comprising a molecule and weakly bound positive or negative ion or an ion formed by the loss of a proton from a molecule. This term was used in mass spectrometry from the late 1960s after the development of chemical ionization but has been deprecated in recent terms recommendations due to what is perceived as its overly broad use. This letter argues that the term is well defined and has a long history of use in mass spectrometry and other fields and should be considered as a recommended term.

Mass Spectrometry Terms: Quasi-molecular ion