Detector to detector variation

Chromatography Forum: GC Archives: Detector to detector variation
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Friday, August 15, 2003 - 09:13 am:

Hello I just installed an agilent 6890 in our lab and i am tryign to prove that i have done the modifications and installation correctly. Fortunately the GC doesn't have to be qualified (IQ,OQ,PQ) but i would like to show that it can produce results equivalent to the 6850 we were using before. Anyway to make a long story short i ran 5 replicate Residual Solvent standard injections and got %RSD values ~0.5% and R2 values ~0.9999 and the peak shapes are at least as symetrical as on the 6850 but, the area for all componenets is about 90% the area for the same peaks on the 6850. My question is; is there detector to detector variation or should i expect the results be equivalent. It is possible that i prepared the standards wrong and that is something i have considered but i'd like to get some feedback on this before i'll admit i made a mistake. Thanks Nat


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Sunday, August 17, 2003 - 11:59 am:

Nat,

There are a lot of possible reasons for this, most of which are not due to any mistake on your part. Things to consider are:

1. use the same syringe and sample on both instruments.
2. your detector fuel gas flows (assuming it's an FID) may be slighly different
3. are your injector split/splitless conditions exactly the same?

Regards,

Ralph


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Monday, August 18, 2003 - 08:56 am:

Ralph,
Thanks for the suggestions you're correct it is an FID and all of my conditions were the same and i am using static headspace w/ the same headspace autosampler . However, i reprepped the standards i was using and i'll be damned if i didn't make a mistake on the earlier prep. The mean area for all components came out w/in 2-3 % of previously run sets.


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