Calibrating a PSD Spectrum
8.3.5 Changing the Precursor Mass
When analyzing the composite spectrum, you may find that the observed fragments and sequence are not consistent with the precursor mass used to acquire the .DAT file. For example, you acquired the data with a precursor mass of 1,000.5 Da, and while examining the data in Data Explorer, you realize that the data may correspond to a precursor mass of 1,000 Da or 1,001 Da.
You can change the precursor mass in the Data Explorer software and regenerate the composite spectrum to observe whether the mass accuracy of the fragment ions improves with a different precursor mass specified.
Before changing the precursor mass, note the following points:
•The Change Mass function changes the value for mp in
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does not change the value for tp. | ||
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•Use the Change Mass function only if the precursor mass used to acquire the data does not correspond to the sequence you are observing in Data Explorer.
•Do not use the Change Mass function to correct a precursor mass that you incorrectly typed before acquiring. The precursor ion flight time associated with the incorrect mass is stored in the .DAT file and will yield invalid fragment masses even if you correct the precursor mass. You must specify the correct precursor mass and reacquire the data to obtain correct mass and flight time values to yield a valid fragment mass calibration.
Data Explorer™ Software User’s Guide |