Gain Drop Monitoring - Waters GCT Premier Operator's Manual

Gain drop monitoring

When the detector on the GCT Premier is hit with a very large signal it uses
up the available electrons with the result that the detector gain drops until
the electrons have been replenished. The effect of this gain drop is that all the
peaks in a spectrum are reduced in intensity, and may not be seen at all in an
extreme case. Furthermore the incorrect signal intensity means that the
DDTC software does not work correctly and so accurate mass measurements
will be compromised.
The Gain Drop Monitoring software tries to prevent this from happening by
monitoring an ion signal that should be constant – in this case the constant
signal from the reference mass used as a lock mass. If the gain of the system
drops below 80% the lock mass will apparently drop in intensity then the
software will stitch in the complete spectrum from the low intensity data,
which the large signal strike has not affected. This retains the accurate mass
measurement. This process is illustrated in the figure below.
See also: Gain Drop Monitoring on page B-44.
Gain drop monitoring:
Gain drop monitoring G-13