AB Sciex QTRAP 4500 LC/MS/MS system, System User'S Manual, Page: 59 / 138

Operating Instructions — Acquisition Methods
System User Guide 4500 Series of Instruments
RUO-IDV-05-0264-A 59 of 138
2 EP (Entrance
Potential)
Compound The EP parameter controls the
potential difference between the
voltage on Q0 and ground. The
entrance potential guides and
focuses the ions through the high-
pressure Q0 region.
Use the preset value.
All
2 Q0 Trapping Compound The Q0 trapping parameter controls
the storage of ions in the Q0 region.
It is used to increase sensitivity and
duty cycle by trapping ions in the Q0
region while ions are being mass-
selectively ejected from the LIT. Use
fixed fill time with this parameter.
Either select or clear the feature
based on the experiment.
The recommended fixed fill time to
use with Q0 trapping is 20 ms or
greater.
EMS, EMC,
EPI, ER, and
MS/MS/MS,
3 CAD Gas Source and
gas
The CAD parameter controls the
pressure of collision gas in the
collision cell during Q3, MS/MS-type,
and LIT scans. For Q3 scans, the
collision gas helps to focus the ions
as they pass through the collision
cell. The preset for the CAD
parameter is in fixed mode. For MS/
MS-type scans, the collision gas aids
in fragmenting the precursor ions.
When the precursor ions collide with
the collision gas, they can dissociate
to form product ions. For LIT scans,
the collision gas helps to focus and
trap ions in the LIT.
Use the preset value and optimize for
the compound.
Q3 MI, Q3
MS, MRM,
Prec, NL,
EMS, ER,
EPI,
MS/MS/MS,
EMC, and
TDF
Item
Parameter Parameter
Type
Use Scan Type