A triple-quadrupole mass spectrometer, also known as QqQ, is a tandem MS method in which the first and third quadrupoles act as mass filters and the second causes fragmentation of the analyte through interaction with a collision gas—it is a radiofrequency-only quadrupole, and can be used in either SIM or scan mode. The method can be used to obtain structural information or for quantitation. For structural mass spec, a common sequence is product ion scan, precursor ion scan, and neutral loss scan, followed by selected reaction monitoring (SRM) or multiple reaction monitoring (MRM).
