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In its simplest form the process of mass analysis in LC-MS involves the separation or filtration of analyte ions.
Introduction to Mass Analysis. In its simplest form the process of mass analysis in LC-MS involves the separation or filtration of analyte ions (or fragments of analyte ions), created in the Atmospheric Pressure Ionisation (API) interface or in the regions between the API interface and the high vacuum region of the mass analyser. The analyte and fragment ions are plotted in terms of their mass-to-charge ratio (m/z) against the abundance of each mass to yield a mass spectrum of the analyte as shown.
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As long as x and y, which determine the position of an ion from the centre of the rods, remain less than ro, the ion will be able to pass through the quadrupole without touching the rods (resonant, non-collisional, or stable trajectory).
When the ion is caused to oscillate with a trajectory whose amplitude exceeds ro it will collide with a rod and discharge or pass out of the mass analyser and not be detected (unstable or collisional trajectory). Thus for any particular m/z value the passage of the ion through the quadrupole is dependent upon U, V, ω and ro.
The trajectories described for the ions through the quadrupole are complex and cannot be described in a simple way, because they include a large number of physical variables that affect the instantaneous electric fields experiencedby the ions. See more Mass analyzer pages here >>