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Triple quadrupole mass spectrometers are the industry standard for quantification of small molecules. Ions are typically transmitted through the first two quadrupoles then separated by mass-to-charge ratio (m/z) in the third quadrupole to obtain a molecular weight measurement. Ions of one m/z type can be selectively transmitted through the first quadrupole, then fragmented in the second quadrupole - the collision cell - by filling the quadrupole with an inert gas such as nitrogen or argon. The ions are injected into the collision cell at a higher energy and the collisions with the gas causes ionic kinetic energy to be translated into internal energy, leading to bond cleavage. The cleavage products are then separated by m/z in the third quadrupole, providing an MS/MS spectrum for structural analyses. Triple quadrupoles are often operated in multiple reaction monitoring mode, where the quadrupoles are set to transmit, fragment and detect only certain masses. This provides a very high sensitivity screen that is useful in metabolomics and other analyses where the samples are in a complex mixture of other species. The CNRU Mass Spectrometry Facility primarily uses an Applied Biosystems API 4000 and a newly acquired API 5000 for small molecule, hormone and pharmacokinetic studies.
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