Correcting Tailing Sample Peaks for Particularly
Active Components
Possible Cause
Solution
Active sites in the injector insert
or liner
Change or clean the injector insert. If necessary,
silanize it.
Active sites or degraded phase
present in the column
Remove the front 15 cm of the column and reinstall it.
If the retention times are changing, or if cutting the
column does not fix the problem, replace the column.
Correcting Low Response and Severe Tailing with
High Boiling Point Compounds
Possible Cause
Solution
Injector not hot enough to
vaporize high boilers
Increase the temperature of the injector
High levels of column bleed
masking component peaks
Condition the column at 30 °C below its maximum
operating temperature. Switch to a high temperature
column if conditioning does not help.
High levels of silicone or other
contamination are coated on
the ion trap surfaces
Clean the ion trap as outlined in the Maintenance
section.
Insufficient vaporization of the
higher boiling point components
Raise the injector temperature and lower the injection
speed.
Trap temperature is too low
Increase the trap temperature in increments of 20 °C.
Correcting Leading Sample Peaks (Reverse Tailing)
Possible Cause
Solution
Column overhead due to injection of
excessive amounts of a component
Dilute the sample, or perform a split
injection.
Degradation of the stationary phase
Change the column.
Carrier gas velocity is too low
Increase the carrier flow rate.
Correcting Poor Resolution
1
Possible Cause
Solution
Column temperature or program is not
optimized
Modify the method (e.g., slow the column
ramp rate) to improve the separation
Carrier gas flow is not optimized
Decrease the carrier gas linear velocity to
improve the resolution.
Column cannot separate certain species,
(e.g., those with similar boiling points)
Use a more polar column.
Column stationary phase is degraded,
resulting in poor efficiency
Replace the column.
1
Peaks are not well separated, e.g., 2,6-dimethylphenol and
2-ethylhexanoic acid in the COLTEST mixture.
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Summary of Contents for 4000 GC
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