Chromatography Forum

Hi All,

I am looking for some ideas to help fix a problem I'm experiencing analysing FAME on a BPX70 column (Clarus500 GC). It has been noticed that during a sequence there is a random error in which the chromatography of a smaple deteriorates so instead of nice sharp peaks, they become broad and short. This problem continues until until the peaks become broader and broader until a flat baseline is observed (with the exception of the solvent peak which remains unchanged).

Baking the column tends to remedy this but i am trying to find the underlying problem that is causing this nuisance.

No changes have been made to the instrument set up apart from routine maintenance (ie septa and liner changes) but there appears to be no connection as to when the maintenance is performed and the porr chromatography is observed.

Any thoughts would be welcome.

Steve

You could give us more details. For instance, you haven't mentioned about the area counts, or if the retention times shift, etc.

Anyway, you could check the split vent as the tubing may be dirty.

Cheers!

I've been doing FAME analysis for over 30 years, but don't know a BPX70 column, not at work yet. We've used cyanopropylsilicone columns for years, and I also mean that the columns also last a long time.

1. Is your inlet temperature high enough, like 250 C ? Before computerized GCs, when one cooled the inlet to change septum, some forgot to restore the heat to the inlet, and didn't notice. Don't ask me how I knew that...

2. What is your sample preparation technique, like are you extracting into hexane or injecting straight esters (we extract).

the chromatography of a smaple deteriorates so instead of nice sharp peaks, they become broad and short. This problem continues until until the peaks become broader and broader

When the FAME peaks on my DB-23 capillary column start to broaden and tail, I replace the injection liner and peak shape is usually restored. Occasionally I have to cut off a meter of the inlet end of the column.