User guide

378 Advanced User Guide
14 GC Output Signals
Column Compensation
In temperature programmed analysis, bleed from the column
increases as the oven temperature rises. This causes a rising
baseline which makes peak detection and integration more
difficult. Column compensation corrects for this baseline rise.
A column compensation run is made with no sample injected.
The GC collects an array of data points from all 4 detectors,
whether installed, off, or working. If a detector is not installed
or is turned off, that part of the array is filled with zeros.
One array (Column compensation 1) can be created for analog
signals. Two independent arrays (Column compensation 1 and
2) can be created for digital signals.
Each array defines a set of curves, one for each detector, that
can be subtracted from the real run to produce a flat baseline.
The next figure illustrates the concept.
All conditions must be identical in the column compensation
run and the real run. The same detector and column must be
used, operating under the same temperature and gas flow
conditions.
Chromatogram with
rising baseline
Chromatogram with
column compensation
Blank column
compensation
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