"Fragment ions" refers to smaller pieces of molecules that are produced when a larger molecule breaks apart. These fragments can provide important information about the original molecule's structure and composition. Full definition
SONAR can catalog a complete sample with precursor and fragment ion spectra from a data independent analysis (DIA) experiment in a single sample injection, giving researchers quantitative and qualitative information about the proteins or metabolites. (sciencemag.org)
The ion at m / z 153 corresponded to the LPA - specific fragment ion. (elifesciences.org)
The LTQ - Orbitrap Velos MS / MS data were first processed by in - house software DeconMSn [21] accurately determining the monoisotopic mass and charge state of parent ions, followed by SEQUEST search against the IPI database in the same fashion as described above, with the exception that a 0.1 - Dalton mass tolerance for precursor ions and 1 - Dalton mass tolerance for fragment ions were used. (journals.plos.org)