236 Advanced Operation Manual
7 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
profile
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