Mass spectrometry techniques rely on a mass analyzer to separate ions of different molecular weight in order to afford differential or specific detection of particular molecular ion of certain mass/charge ratio. One common mass analyzer is the quadrupole mass analyzer common in liquid chromatography mass spectrometry (LC-MS) applications.
In the gentle ionization technique known as matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF mass spectrometry), all the ions are suctioned into the instrument via a vacuum flight tube. As the molecular ion of different molecular weight fly towards the mass detector under the attraction of an applied electric field, the heavier molecular ion experiences a longer flight time compared to the less heavy molecular ion. Hence, molecular ions of different molecular weight arrive at the mass detector at different times, and thus, there is separation of the molecular ions of different molecular weight. Therefore, the time of flight (TOF) flight tube serves as a mass analyzer in this case. There is possibility of mass interference in the case of molecular ions of very similar molecular weight. But, in general, the technique of using TOF flight tube to separate molecular ion of different molecular weight has a sound theoretical and practical basis.
Category: analytical chemistry,
Tags: time of flight tube, flight time, mass analyzer, separation of mass/charge, mass/charge ratio,
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