An alternative cause of calibration failure is from contamination or background peaks.
If a contamination or background peak lies within one of the peak matching windows,
and is more intense than the reference peak in that window, then the wrong peak is
selected. Under some conditions this may happen with PEG. There are two ways to
counter this:
•
If the reference peak is closer to the centre of the peak window then the peak
window can be narrowed until the contamination peak is excluded. Take care to
ensure that no other reference peak is excluded.
•
If the reference peak is not closer to the centre of the peak window, or if by
reducing the window other reference peaks are excluded, then the calibration can
be edited manually.
Manual Editing of Peak Matching
If an incorrect peak has been matched in the calibration process, this peak can be
excluded manually from within the on-screen calibration report.
Using the mouse place the cursor over the peak in the acquired spectrum and
click with the right mouse button.
The peak is excluded and is no longer highlighted.
If the true reference peak is present then this can be included in the calibration by the
same procedure.
Place the cursor over the required peak and click with the right mouse button.
The peak is matched with the closest peak in the reference spectrum.
Manually editing one peak does not affect the other matched peaks in the calibration.
Saving the Calibration
When the instrument is fully calibrated the calibration can be saved under a filename
so that it can be recalled for future use. For example, it is possible to save calibrations
for use with different ionisation modes, so that when an ionisation source is switched
the corresponding calibration is recalled.
The recalled calibration has the same constraints of mass range and scan speed. The
ion energy and resolution settings used for the calibration acquisition are also recorded
as these can have an effect on mass assignment.
Mass Calibration
Page 137
Quattro Ultima
User's Guide
Summary of Contents for Quattro Ultima
Page 2: ...Quattro Ultima User s Guide...
Page 68: ......
Page 100: ...Data Acquisition Page 100 Quattro Ultima User s Guide...
Page 117: ...Mass Calibration Page 117 Quattro Ultima User s Guide...
Page 140: ...Mass Calibration Page 140 Quattro Ultima User s Guide...
Page 212: ...Maintenance and Fault Finding Page 212 Quattro Ultima User s Guide...
Page 222: ...Reference Information Page 222 Quattro Ultima User s Guide...
