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Chapter 7 Data Explorer Examples
7-8 Applied Biosystems
7
7.1.3 Determining if a Peak
is Background Noise
Overview To determine if spectral peaks represent low-level
components or if they are due to solvent contribution, you can:
• Subtract the spectral peaks from the chromatogram
• Create an extracted ion chromatogram for the spectral
peaks
Subtracting
spectral peaks
The following example uses the chromatograms and spectra
from Section 7.1.2, Deconvoluting and Evaluating Unresolved
Chromatographic Peaks. It illustrates how to subtract baseline
and determine if the spectral peak observed at 391 Da
(Figure 7-5 on page 7-7) is eliminated.
To subtract spectra:
1. Activate the first extracted ion chromatogram in
Chromatogram window (see Figure 7-4 on page 7-6).
2. From the Process menu, select Add/Subtract Spectra.
3. Click , then right-click-drag over the peak in the
extracted ion chromatogram.
The spectrum range is displayed in the Spectra To Be
Added list in the Add and Subtract Spectra dialog box
(Figure 7-6).
4. In the Add and Subtract Spectra dialog box, click
anywhere in the Spectra To Be Subtracted list.
5. In the TIC, right-click over a region of baseline that does
not contain any peaks.
NOTE: When selecting spectra to subtract, select from
the TIC. The baseline in the extracted ion
chromatograms is for a selected mass and does not
represent all components which may be present.