Quadrupole Mass Analyzer - Triple Quadrupoles

Triple Quadrupoles

A linear series of three quadrupoles can be used; known as a triple quadrupole mass spectrometer. The first (Q₁) and third (Q₃) quadrupoles act as mass filters, and the middle (q₂) quadrupole is employed as a collision cell. This collision cell is an RF-only quadrupole (non-mass filtering) using Ar, He, or N gas (~10−3 Torr, ~30 eV) for collision induced dissociation of selected parent ion(s) from Q₁. Subsequent fragments are passed through to Q₃ where they may be filtered or fully scanned.

This process allows for the study of fragments (daughter ions) that are crucial in structural elucidation. For example, the Q₁ may be set to 'filter' for a drug ion of known mass, which is fragmented in q₂. The third quadrupole (Q₃) can then be set to scan the entire m/z range, giving information on the intensities of the fragments made. Thus, the structure of the original ion can be deduced.

The arrangement of three quadrupoles was first developed by Jim Morrison 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 Dr. Christie Enke and graduate student Richard Yost in the late 1970s.