Chemical Sciences: A Manual for CSIR-UGC National Eligibility Test for Lectureship and JRF/Triple quadrupole mass spectrometer

A triple quadrupole mass spectrometer is a tandem mass spectrometer consisting of two quadrupole mass spectrometers in series, with a (non mass-resolving) radio frequency (RF) only quadrupole between them to act as a collision cell for collision-induced dissociation. The first (Q₁) and third (Q₃) quadrupoles serve as mass filters, whereas the middle (q₂) quadrupole serves as a collision cell. This collision cell is an RF only quadrupole (non-mass filtering) using an inert gas such as Ar, He or N₂ gas to provide collision-induced dissociation of a selected precursor ion that is selected in Q₁. Subsequent fragments are passed through to Q₃ where they may be filtered or scanned.

Waters Quattro II triple quadropole mass spectrometer (center).

Structural mass spectrometry

This alignment of two mass spectrometers in succession with a collision cell (e.g. a collision quadrupole) in between allows structural mass spectrometry to be performed. For example, the Q₁ may be set to select an ion of a known mass, which is fragmented in q₂. The third quadrupole (Q₃) is then set to scan the entire m/z range, giving information on the sizes of the fragments made. From the ion fragmentation information, the structure of the original ion can be deduced.

History

The arrangement of three quadrupoles was first developed by Morrizon of LaTrobe University, Australia for the purpose of studying the photodissociation of gas-phase ions. The first triple-quadrupole mass spectrometer was developed at Michigan State University by Enke and Yost in the late 1970's.