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*   Thresholding
Thresholding is a data processing method that analyzes every scan to reduce ion intensities or delete spectral peaks if algorithmic criteria have been met. The main purpose of thresholding is to eliminate noise or peaks originating from minor components that are not of interest. Thresholding requires fulfilling the condition that the intensity of noise peaks is smaller than the intensity of a signal and that the noise peaks count is significantly higher than the signal peaks count.
Note  In contrast to Baseline Correction and Noise Elimination (see Baseline Correction and Noise Elimination), which operates in a chromatographic time domain, the thresholding feature processes each scan as a stand-alone, independent object that ignores the previous or following scans. Setting thresholds can significantly shorten JCD computation time for large chromatograms.
This topic includes the following topics:
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To apply thresholding to your data
1.
Click the Chromatogram Processing Utilities button, , and choose Thresholding.
The Threshold Filter dialog box opens. See Threshold Filter dialog box.
2.
3.
Click Calculate.
4.
Threshold Filter dialog box
Marks the threshold peaks in red when they are large enough to be above threshold value (the point where the Mass Frontier application preserves peaks). No peaks are removed. The same logic is applied for FISh filtering.
Apply Threshold to Top Stage Only
Specifies that only MS1 (full scan) scans are processed.
Minimal Remaining Peak Count
Minimal Peaks per Scan
In the Linear Fit or Histogram method, the calculated threshold value is multiplied by this value.
In the Median method, this value is used for calculation of filter length.
Apply Threshold to Spectra with
Peak Count Higher Than
Specifies that algorithmic thresholding is applied to spectra with several peaks higher than the specified value.
Specifies that the algorithmic threshold is applied to spectral peaks with an intensity lower than the specified value.
Opens the Save Threshold Parameters File dialog box where you save your current parameters to a threshold parameters file (.threshold.par).
Opens the Open Threshold Parameters File dialog box where you can choose a threshold parameters file (.threshold.par) to load.


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Related Topics:
  Specifying Methods
  Using the Threshold Filter Wizard
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