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Calibration of GC machine with Acetaldehyde
Posted: Mon Jan 22, 2018 12:52 pm
by Rima Dokmak
hello,
we measure the Acetaldehyde content in the PET Preforms.
we use the gc machine (agilent 6890) with FID,
for the GC calibration, we use the standard Acetaldehyde, purity 100%, concentration 1000 microgram/mL from Accustandard.
I am asking if it is possible to use one single point as a calibration or multiple points and how do we calibrate it.
thanks,
Re: Calibration of GC machine with Acetaldehyde
Posted: Wed Jan 24, 2018 3:01 pm
by rb6banjo
With a single point calibration, you first must prove that the detector responds linearly to your analyte coming out of your matrix. Once you feel comfortable that is the case, then I'm ok with doing single point calibration AS LONG AS your samples do not contain wildly different concentrations of the analyte. You need to use a standard that is of a similar concentration of your analyte. You are fortunate that you have chosen a flame detector because it is generally very linear over a very wide range of concentrations.
If you don't have a method, you need to get a book that will teach you about the analysis of solid materials using headspace sampling. I would recommend:
"Static Headspace Gas Chromatography. Theory and Practice" by Bruno Kolb and Leslie Ettre. Wiley-VCH is the publisher. There is a very good section in one of the chapters (4.1.3 in the first edition, 1997) that describes the critical things you have to consider to analyze solids like this.
There is much to consider when developing these types of methods. Too much to take on in this forum.
Re: Calibration of GC machine with Acetaldehyde
Posted: Tue Feb 20, 2018 9:42 am
by RimaDok
when using the single or multiple calibration points, i should have the same results, right?
and what should the difference be between the results of single and multiple point calibration?
can you provide me with information about companies that use the HS-GCFID Machine to test the Acetaldehyde in PET preforms.
thanks,
Re: Calibration of GC machine with Acetaldehyde
Posted: Tue Feb 20, 2018 2:07 pm
by rb6banjo
If you are properly calibrated, you should get the same answer no matter what. The answer is what it is.
You may only go to a single point If you have verified that your system is well behaved and that only running 1 point for the calibration standard is good enough for your purposes.
Most companies are not going to share their analysis conditions in the open like this forum. I suggest that you find some app notes by instrument manufacturers who have done it. It'll give you someplace to start. For example:
https://www.agilent.com/cs/library/appl ... 4355EN.pdf