Chromatographic Troubleshooting
Retention time symptoms
207
Retention time symptoms
Retention time drift
Retention time drift is a steady increase or decrease of retention times in
successive runs. Erratic times (both directions) are discussed below as
retention time wander.
1. In a series of runs, retention times suddenly increase:
This may be due to an oven temperature change or to change in
flow; verify setpoints.
A blown septum is a possibility. If this happens, the change is
probably at the beginning of a run.
The carrier gas tank may be nearly empty.
2. In a series of runs, retention times suddenly decrease:
This is likely to be due to a setpoint change, either in oven
temperature or in carrier gas flow rate; verify both.
Retention time wander (reproducibility)
1. Retention time reproducibility is erratic throughout the run:
If the runs are made with manual injection, the suspect is
injection technique. Variation in time between sample injection
and pressing
START
causes variation in retention times. With
automatic injection this possibility is minimized.
Oven temperature variation may cause this; monitor oven
temperature during a run to check this.
