-
- Posts: 3
- Joined: Wed Apr 09, 2014 8:43 pm
FAMEs on GCFID.
In the past, we added a surrogate/recovery standard (methyl tridecanoate) to our samples before transesterification (TE).
After transesterification and before running on instrument, we added our internal standard (pentadecane) to all samples, Calibration Verification Standard (CVS), standard curve.
Now, we do not use pentadecane, but we have migrated to using just an internal standard throughout, adding methyl tridecanoate to our samples, running through transesterification, and running an aliquot of that through the GCFID. Thus, for our standard calibration curve, our internal standard check is also methyl tridecanoate. The responses between the two - with no TE (standard curve) and with TE - varies. No TE - 8736971.55; with TE - 7440853.522
I don't feel like the methyl tridecanoate alone is enough of a check, aside from having QC samples (the procedure is done with TE) and a CVS (the procedure is done just like the standard curve).
Is the method we run now, ok. Or should I add a surrogate/recovery standard to my unknown samples? If so, how can I use excel to determine that these surrogate/recovery standard numbers are acceptable and consistent?
I have an excel sheet that calculates for the method now and would prefer not to make a huge change to it. Can I just run some methyl ester alone with the internal standard and check for variability there?
Any suggestions would be great.
Thanks in advance,
MaryL14