Mass spectrometers (or mass analyzers) measure molecules according to their mass to charge ratio (m/z). As a prerequisite, molecules must be positively or negatively ionized or charged. Electrospray ionisation (ESI) technology has been shown to be a very robust and user-friendly ionisation method.
A tandem or triple quadrupole mass spectrometer consists of two mass analyzers connected to each other via a collision cell. In the first mass analyzer (Q1), ions are separated according to their mass to charge ratio. These precursor ions are then transferred into a collision cell (Q2) where they are fragmented by physical collision with a gas, usually nitrogen or argon. These fragments or product ions are then introduced into the second mass analyzer (Q3), separated and detected. A precursor and product ion pattern is extremely selective for a given substance.
Multiple Reaction Monitoring (MRM)
Multiple Reaction Monitoring is the most selective of all measuring modes. One precursor ion is selected in Q1 and is then fragmented in the collision cell (Q2). From these fragments ions, only one is selected and analyzed in Q3. All other fragments and interfering substances are not detected. The result is excellent selectivity and sensitivity.
Learn how Mass Spectrometry can help the Clinical Laboratory by viewing this short video: