Micromass Quattro Ultima, User Manual

Page: 107 / 227

Selecting Parameters
A number of parameters needs to be set before a calibration is started. Default
parameters are set when the software is initially loaded which usually give a suitable
calibration, but under some conditions these may need to be adjusted.
Automatic Calibration Check
This is accessed from Edit , AutoCal Check Parameters... .
It is here that limits are set
which the calibration must attain
before the instrument is
successfully calibrated. Two
user parameters can be set.
Missed Reference Peaks
sets the maximum number of
consecutive peaks which are not
matched when comparing the
reference spectrum and the acquired calibration spectrum. If this number is exceeded
then the calibration fails. The default value for this parameter, 2, is suitable in most
cases.
Maximum Std Deviation is set to a default of 0.20. During calibration the
difference between the measured mass in the acquired calibration file
and the true mass in the reference file is taken for each pair of matched
peaks. If the standard deviation of the set of mass differences exceeds
the set value then the calibration fails. Reducing the value of the
standard deviation gives a more stringent limit. Increasing the standard
deviation means that the requirement is easier to meet, but this may
allow incorrect peak matching. Values greater than 0.20 should not be
used unless exceptional conditions are found.
Apply Span Correction
should always be left on. This allows different mass ranges
to be scanned, within the calibrated range, without affecting mass assignment.
Check Acquisition Calibration Ranges causes warning messages to be displayed
if an attempt is made to acquire data outside of the calibrated range for mass and scan
speed. It is advisable to leave this on.
Mass Calibration
Page 107
Quattro Ultima
User's Guide