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FID response difference between two Agilent 7890A GC!
Posted: Sun Jun 21, 2009 2:00 am
by bily200677
Hello, everyone! Currently , we do valiations work on residual solvent method by Agilent 7890A GC system . There are two same instrument in our lab. Yesterday , we did the intermdate precision test using another 7890A ,but today morning , we found the object peaks had higher response in the second 7890A system . Compare these dates , we found the peaks height and area are about
three ~four time of the first instrument! Note , the concentration of the standard solutions are same , the column are the same one , the condition are same , only the instrument is different! i am confused by these data, what's the reason?
Anyone had this experience ? or any advice for me?
thank a lot!
bily
Posted: Sun Jun 21, 2009 7:02 am
by Consumer Products Guy
Split ratios could be different, air/hydrogen/auxiliary gas to detector could be different. Column protrosion through ferrule into inlet could be different. Syringe sizes could be different even if softmare setting matches. Good hunting.
Posted: Sun Jun 21, 2009 4:15 pm
by Schmitty
Also range and attenuation differences. If you are collecting with Millennium/Empower, there may also be a difference in the instrument method used, i.e. the scaling factor.
Posted: Mon Jun 22, 2009 6:41 am
by krickos
Hi
Adding sealing of the headspace vials as a possible issue.
Posted: Wed Jun 24, 2009 3:27 pm
by at_om
Hi Bily!
I already transferred methods from a 6890 to a 7890 both with FID and had very similar area results. Is the autosampler also identical? Sample introduction in inlet could make a difference. Is the column distance in inlet and detector the same length in both instruments? You really have to check all the method parameters.
Good luck!
Regards,
At_om
thanks a lot to all
Posted: Wed Jul 01, 2009 12:35 am
by bily200677
Firstly , i should say "thanks" to everyone who provided the helpful advises for me ! this problem i think must be somthing wrong in the second instrument . Even if the everything seem good in the second 7890A , but check the past chromatogram and data, the second instrument performace was normal . SO , I think the second instrument went wrong. Now, we ready to do this test in another 6890GC ( because the second 7890A is not availble now), i believe the results will be acceptable !
thanks you all again !
bily