Continually changing retention times

Chromatography Forum: GC Archives: Continually changing retention times
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Friday, June 30, 2000 - 09:26 pm:

Dear Sir/Madam,

I am using a PE Autosystem GC for doing basic separations. We are using J&W DB-5 megabore column 0.53umx30m w/1.5micron film thinkness.

We do see drift of retention times, but for the most part the drift is small enough that it doesn't affect peak identifications. There is one analysis we are conducting in which the peaks of interest are in such low concentrations that these retention time changes do affect peak identification. We are using TurboChrom ver 6.21 and for the most part I have found it useful. I have not been able to identify a way to re-adjust retention times automatically (i.e. have some sort of reference peak).

I am open to any suggestion,

Troubled Chromatographer


Top of pagePrevious messageNext messageBottom of pageLink to this message  By H.Schnorbus on Sunday, July 2, 2000 - 11:41 pm:

Changing retentiontimes can various reasons.
1. Septum leak (longer rt.-times) 2. Column connection (Inj.side loose) 3.If using a splitter and you observe shorter Rt. then the splitter is clogged up. 4.Plugged column exit (detector side) Column to far inside the FID- connection.Look at these suggestions in that order


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Les on Monday, July 3, 2000 - 08:15 am:

What type of head pressure control are you using? EPC under @20 PSI is not as constant as a mass flow controller.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Mark on Thursday, January 18, 2001 - 05:45 am:

I agree with the above statements, but you should also consider column contaminations. Many columns are effected by moisture or by heavies. You should try burning out your column on a regular basis, changing septa, repacking injector linings, ect.

If you are looking for a program that will modify the flows (ppc only) so that your retention times are corrected by a program, then you should look into the GC TUNE application of Turbochrome


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