If retention time for all peaks becomes longer, the following are possible causes:
If the column flow has been reduced, the retention time will be longer.
Check the initial oven temperature. Make sure it has not been decreased. Decreasing the initial oven temperature increases retention times for all compounds.
Active sites can cause a number of symptoms. The most common symptom is peak tailing. Others symptoms include peak fronting and increased retention times.
Replace the injection port liner with a new, deactivated liner.
Make sure the liner is installed properly. Column fragments in the liner can cause peak tailing.
Replace the injection port seal.
Remove the column from the injection port. Break off the first 10 cm. Reinstall the column in the injection port.
See the documentation supplied with the GC for help with injection port maintenance.
Leaks in the septum, injection port seal, and column nut allow sample to escape. Tighten fittings or replace injection port components as necessary.
See the documentation supplied with your GC for instructions for injection port maintenance.