56 Agilent 6400 Series Triple Quad LC/MS Concepts Guide
3 Agilent Triple Quadrupole MS and Sensitivity
Front-end ion optics
Skimmer Agilent uses a small diameter skimmer orifice with very short
distances from the capillary to the skimmer to the octopole.
Consequently, more of the ions exiting the capillary are
captured by the ion octopole guide, thereby keeping the ion
beam very tightly focused.
Octopole 1 Higher multipoles provide better ion transmission over a wider
mass range. The depth of the potential well is steeper for the
higher multipoles (at like voltages), especially those close to the
rods resulting in the loss of fewer ions. This explains the
predominant use of octopoles as ion guides in mass
spectrometers where the main objective is to transmit rather
than filter the ions.
Lens 2 RF The phase of lens 2 is matched to that of the subsequent
quadrupole, MS1 (Q1), resulting in a significantly increased
sensitivity.
Quad mass
filters
The quadrupoles consist of hyperbolic rods that optimize ion
transmission and spectral resolution. There tends to be more
ion loss with circular rods.
Lens 2 RF (transmission of higher masses) Hyperbolic quadrupole and post-filter
Figure 25 Front-end optics
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