When you use the Precursor Fit filter, you can limit the triggering of data-dependent scans if the peaks within the specified window do not match the theoretical pattern above a defined threshold.
For dependent scans, specify a Fit Threshold (%). The dependent scan does not trigger until the Fit value exceeds the specified threshold.
If the Precursor Fit value exceeds the user-specified threshold, the system carries the precursor through the filter to the next filter or adds it to the scan event execution list. If the Fit value is below the user-specified threshold, the system takes no further action.
The following table describes the parameters in the Theoretical Precursor Envelop Fit Properties pane.
Parameter | Description |
|---|---|
Fit Threshold (%) | The Precursor Fit is a comparison of the theoretical precursor isotopic envelop to the observed envelop. The Precursor Fit (normalized between the theoretical and observed envelopes within the Fit Window) must be above the Fit Threshold to pass the filter and trigger a data-dependent scan. This is used to prevent dependent scans when there is a disagreement between the theoretical precursor envelop and what is observed inside the isolation window. Range: 0-100; default: 70 |
Fit Window (m/z) | The Fit window is centered around the candidate ion. If the isolation window size in the dependent scan(s) does not match the fit window size, the fit calculation will not match that of what is isolated. Isolation Offset should not be used when using Theoretical Precursor Fit Filter. Range: 0-3,000; default: 1.6 |