Vacuum conditions in the mass spectrometer
Coupling chromatography with mass spectrometry - Part 1

Whatever the chromatographic coupling, GC-MS or LC-MS, the mass analyzer must always be under vacuum, so as not to interfere with the action of the force field (magnetic or electric, depending on the type of analyzer) directing the movement of ions between their source and the detector.

Typical operating pressures for analyzers range from 10 ^–3 to 10 ^–4 Pa, with quadrupoles and hatches generally tolerating pressures around 5 times higher than magnetic devices.

FT/MS analyzers, on the other hand, require much lower operating pressures.

These pressures depend on the quantities of gas admitted into the mass spectrometer via the interface, the efficiency of the vacuum pumping systems, and the pneumatic impedances of the lines...