Use blank subtraction
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Use blank subtraction

When analyzing a sample, the obtained signal may be caused by analytes as well as by dilution solvents, mobile phases, additives etc. Use the blank subtraction to receive a clean chromatogram with contribution of the analytes only.

NOTE

Starting with OpenLab CDS v2.8, blank subtraction is applied to all signals in your result set, both non-MS and MS.

Example: UV signal before blank subtraction
Figure Example: UV signal before blank subtraction
Example: UV signal after blank subtraction
Figure Example: UV signal after blank subtraction

For injections where a blank signal has been subtracted, an asterisk is shown in front of the signal name, and the [b] tag is added at the end.

NOTE

In the Chromatograms window, the asterisk and tag are only visible in the display modes Separate and by Injection.

NOTE

When both blank subtraction and smoothing settings are used to process data, the system will do blank subtraction first and then smooth the blank subtracted signals.

Blank subtraction on extracted wavelength chromatograms

If you define blank subtraction and extract wavelength chromatograms, the process is as follows:

  1. The application extracts a wavelength chromatogram from the blank, using the sample's processing method.

    Extracted wavelength chromatograms that have been created using the blank's processing method are not relevant here.

  2. The application extracts a wavelength chromatogram from the sample, using the sample's processing method.

  3. Both extracted wavelength chromatograms are subtracted from each other.

Blank subtraction on MS signals

  • Blank subtraction of MS data is a subtraction of two corresponding chromatographic signals (sample TIC minus blank TIC, sample EIC minus blank EIC, or sample SIM minus blank SIM). If no corresponding signal is found (for example, if the blank was acquired with a different fragmentor voltage than the sample), no subtraction occurs.

  • Blank subtraction of MS data subtracts chromatographic signals without affecting MS spectra.

  • If the blank has a higher background or response than the sample, blank-subtracted TIC, EIC, or SIM chromatograms may show negative abundance values.

  • When using blank subtraction, all available signals will be subtracted. For MS data, this includes all TIC Scan and TIC SIM chromatograms, and all extracted chromatograms (EICs and SIMs).

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