Applied Biosystems Data Explorer 4 Series User Manual page 357

Selecting
calibration peaks
for optimum mass
accuracy
To improve calibration statistics, you can select the same
fragment ion from more than one segment. Monoamino acid
fragments (immonium ions) below 150 Da are useful for this
purpose. Because the segments have been collected with
different PSD Mirror Ratios, the software allows you to add the
same mass to the list multiple times.
Hint: A calibration reference file called
Immonium_Ions.REF is provided with the software.
To optimize mass accuracy across the entire PSD composite
spectrum (multi-point calibration):
• Select reference peaks from a wide range of segments to
ensure that high and low Mirror Ratios are represented.
• Include peaks with masses that are substantially below
the Max Stitch Mass (for example, up to 50 percent lower
than the Max Stitch Mass.
• Avoid selecting peaks with masses that are above the
Max Stitch Mass.
• Avoid selecting peaks with signal-to-noise ratios less
than 20.
Data Explorer
Calibrating a PSD Spectrum
™
Software User's Guide
8
8-19