Using Mass Spectrometers
Minimizing the Noise of Mass Spectra

Mass Spectra usually include more details than UV spectra. However, they often have an increased noise level. They are considerably affected by the background spectrum, especially with low signal intensity. To use the information of mass spectra in the best possible way, Dionex recommends that you reprocess them, using one of the techniques described here.

Spectra Bunching

To reduce mass spectra noise, you can bunch several single mass spectra to one entire mass spectrum. Spectra bunching can be performed for both peak spectra and retention time spectra.

Use the MS tab page of the QNT Editor to bunch several single spectra to the left and the right of the chromatogram peak together with the peak maximum spectrum to one entire peak spectrum. (For more information about the editor, see Data Representation and Reprocessing  The QNT Editor.)

In the chromatogram, define the range for which to display the entire retention time spectrum. Use the Spectra/I-t Plots Tool to select a range while left-clicking. You can perform this in a UV channel, also.

Subtracting Background Mass Spectra

Background subtraction of mass spectra eliminates the influence of the background on the mass spectra. The background mass spectrum to be subtracted can be defined either for the entire chromatogram or automatically by Chromeleon for each single peak.

The corresponding setting is selected on the MS tab page of the QNT Editor or in the chromatogram. The settings made in the chromatogram are saved to the QNT File of the current sample as well. Thus, your input affects all samples that are evaluated using this QNT File.

For more information, refer to:

 Processing Mass Spectra

Working with Chromatograms  Subtracting Background Spectra

Tracking the Effects of Background Subtraction

You can track the effects of spectra subtraction directly on the mass spectra plot: