Calibrating a PSD Spectrum

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.

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•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™ Software User’s Guide

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