Technical data

40 Agilent 6200 Series TOF and 6500 Series Q-TOF LC/MS System Concepts Guide
1Overview
Front-end ion optics
• Linear axial acceleration
• High pressure collision cell
• High speed digital electronics
The collision cell contains nitrogen, the same gas that is used in
the ion source. The small diameter of the hexapole assembly
assists in capturing fragmented ions.
Why a hexapole? The geometry of a hexapole provides
advantages in two domains: ion focusing and ion transmission.
• The first advantage is in ion focusing where a quadrupole is
better than a hexapole, which is better than an octopole, that
is, quadrupole > hexapole > octopole.
• The second advantage involves ion transmission across
a wide mass range, or m/z bandwidth. In this case, the
octopole is better than the hexapole, which is better than the
quadrupole.
The hexapole is chosen because, overall, it is the best for both
ion focusing and ion transmission.
Collision cell design The collision cell hexapole consists of six
resistively coated rods used to generate a potential difference
across the length of the collision cell.
A potential difference is always present. This ensures that the
precursor ions coming from the quadrupole or fragment ions
generated in the collision cell are transmitted and not allowed
to drift around at random.
Sweeping out the ions in this manner avoids the issue of
crosstalk where residual product ions from a previous
experiment can interfere with the product ion spectrum of
a subsequent experiment. A collision energy voltage is applied
over the accelerating linear voltage to generate fragments or
product ions.
Beam shaping (Vacuum stage 4 for both 6220 TOF and Q-TOF)
In the Agilent 6538 and 6540 UDH Accurate-Mass Q-TOF, ions
enter the ion beam compression technology. Ion beam
compression provides up to a 10-fold compression and cooling