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Selected Ion Chromatogram (SIC)

Mass Frontier enables you to display a chromatogram for a selected ion in a different color. The selected ion chromatogram (SIC) is sometimes called an individual or single ion chromatogram, ion profile. The program can display up to three selected ion chromatograms per window.

To display an SIC for a particular mass-to-charge ratio:

  • Click on the spectral peak of interest on the Scan page

  • Or, select the Data tab and click the m/z value in the mass-to-charge ratio table

  • Or, click the Selected Ion Chromatogram button

In either case a dialog window will appear in which you can change or add the mass-to-charge ratio and confirm your choice. This dialog window allows you to select a color for a particular m/z value.

Mass Frontier extracts the SIC from the original file, and this process can be time-consuming for chromatograms with a large number of scans. However, because Mass Frontier is a multithreading application, you can still use other windows during the SIC extraction.

A selected ion chromatogram is very useful feature for verifying automated component detection and spectra deconvolution results. An SIC helps you to quickly recognize mixture components in a peak region. An SIC of model peaks should be examined for any component you may wish to use in further analysis. Remember that some structural (alkanes) or optical isomers produce almost identical mass spectra and even if you can clearly see two or more maxima in a peak region, an SIC may not reveal a multi-component profile.

An SIC can help you to determine whether or not the composition of the background changes over the course of a run. To view the background profile, extract the SIC of a base peak, or prominent peak, from a scan which is clearly in a non-peak region. If the SIC of a background peak has a variable profile around the peak you are focusing on, choose two scans with different SIC profiles for background subtraction.

 

Background subtraction can be used in conjunction with SIC option. In this case the SIC profiles are extracted from background subtracted scans.

 

Note:

SIC peaks can appear larger on the screen than the corresponding TIC peaks. In reality SIC signals are disproportionally lower than TIC signals, especially if the data was not acquired using the selective ion monitoring mode. It would be impractical to examine minute SIC peaks displayed together with TIC on the screen. Therefore, SIC data are normalized to the maximum of TIC signal and visually enlarged for display purposes.

 

 
 
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