SRI8610 GC. Volatile fatty acids(VFA) detection

[gadhamvr]

Following are the operating conditions:

GC-SRI 8610

Carrier: Helium
Detector:FID
Column: HAYSEPQ 80/100 Packed column

Temperatures: Oven 200 C; Detector:220 C;

I was having good peak areas, in magnitude of 12-15000 for Acetate;propionate;butyrate;

I changed septa, and surprisingly, magnitude of the peak areas reduced immediately by 5 times, to 2000.

I checked for all the leaks, changed the syringe, checked the liner connection,

It is very surprising, that peak areas have dropped in fraction of minute; after septum change.

Any ideas please????

Ramana

[chromatographer1]

Perhaps your sample changed. Are you injecting from the same vial?
These ester analytes are quite volatile. Are they methyl esters, or ethyl, or propyl?

You could have lost them from the source of your sample.

If you ran something before the change of septum which should remain stable and is not that volatile you could run it again to determine if the problem lies in the GC or in the handling of the ester sample.

best wishes,

Rod

[gadhamvr]

Thank You Rod,

I have new calibration standard each time.
These are organic acids: Acetic acid; propionic acid; butyric acid;

So, i am reluctant to blame standards.