Unexpected Peaks in Tandem Mass Spectra due to Reaction of Product Ions with Water in Mass Spectrometer Collision Cells
Pedatsur Neta, Mahnaz Farahani, Yamil Simon, Yuxue Liang, Xiaoyu Yang, Stephen E. Stein
While determining the fragmentation pathways of positive ions of drugs, pesticides, metabolites, and other compounds, using electrospray ionization mass spectrometry, we noticed that certain product ions react with water in the collision cell. This reaction is due to the presence of water in many types of mass spectrometers and often leads to formation of species that cannot be formed from the precursor ions by known fragmentation pathways. As a result, tandem mass spectra may contain unexplained peaks and may appear incorrect. Furthermore, MRM (multiple reaction monitoring) results may be distorted by the occurrence of such reactions. In this work we examine a number of compounds that exhibit this behavior and attempt to determine which product ion types are susceptible to reaction with water. Examples of ions reacting rapidly with water include phenyl and certain substituted phenyl cations, benzoyl type cations formed from protonated folic acid and similar compounds by loss of the glutamate moiety, product ions formed from protonated cyclic siloxanes by loss of methane, product ions formed from organic phosphates, and certain negative ions. The reactions of product ions with water were observed in several types of mass spectrometers under standard operating conditions and confirmed by MS3 experiments. Moreover, the rates of reaction for certain product ions with water were determined by using an ion-trap mass spectrometer with variable activation time. These often unavoidable reactions must be taken into account when annotating peaks in tandem mass spectra and when interpreting MRM results.
, Farahani, M.
, Simon, Y.
, Liang, Y.
, Yang, X.
and Stein, S.
Unexpected Peaks in Tandem Mass Spectra due to Reaction of Product Ions with Water in Mass Spectrometer Collision Cells, Rapid Communications in Mass Spectrometry, [online], https://doi.org/10.1002/rcm.7055.
(Accessed October 4, 2022)