The mass analyzers (Q1 and Q3 quadrupoles) are square arrays that are charged with a variable ratio of RF voltage and DC voltage. A particular set of RF and DC voltages applied to the quadrupole rods generates an electric field that gives stable oscillations to ions with a specific m/z and gives unstable oscillations to all others.
When the MS applies one particular set of RF and DC voltages to the mass analyzer rods, only ions of one m/z (for example, m/z 180) are maintained within bounded oscillations, as their velocity carries them through the mass analyzer. At the same time, all other ions undergo unbounded oscillations. These ions strike one of the rod surfaces, become neutralized, and are pumped away, or they are ejected from the rod assembly.
Later, both RF and DC voltages change, and ions of a different m/z (for example, m/z 181) are allowed to pass, while all other ions (including m/z 180) become unstable and undergo unbounded oscillations. This process of transmitting ions of one m/z after another continues as the RF and DC voltages change in value.
The MS can rapidly and precisely ramp the voltages on the quadrupole rods to obtain a fast scan rate.
The more closely the electric field generated by a set of quadrupole rods approximates a hyperbolic geometry, the better the rods’ operating characteristics are. As a result, the precision hyperbolic surface of the mass spectrometer’s quadrupole rods provide excellent sensitivity, peak shape, resolution, and high mass transmission.