Peptides can be subjected to multiple rounds of fragmentation and mass analysis—a process termed tandem-MS, MS/MS or MSn. By combining the same or different mass analyzers in tandem, such as quadrupole-TOF (Q-TOF) or triple-quadrupole (QQQ) MS, the strengths of different mass analyzers can be leveraged to further improve the capacity for proteome-wide analysis. Simple MS setups such as MALDI-TOF are only used for peptide mass measurements, whereas tandem mass spectrometers are used to determine peptide sequences.