Best ethanol-method with GC-FID?

Chromatography Forum: GC Archives: Best ethanol-method with GC-FID?
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Eija on Thursday, July 15, 2004 - 01:20 am:

Hi, we`d like to analyze ethanol in beer. We are using PerkinElmerGC and TurboMatrix-headspacesampler. Currently we are running an isothermal analyse(115)with n-butanol as an internal std. We`ve had some difficulties on getting the best yield. If anyone knows a good method for ethanol in beer by GC/FID, could you respond. Thanks!


Top of pagePrevious messageNext messageBottom of pageLink to this message  By GC Dave on Thursday, July 15, 2004 - 03:37 am:

Eija,
What exactly do you mean by "good yield"? Perhaps you mean that you are having trouble with optimising the headspace conditions? I have tried 80degC for 20mins to analyse ethanol in water.
If your ethanol content is approx. 0.1 - 10.0% range you might try injecting with an autosampler and split with internal standard and calibration.
However I suppose the headspace will give you a cleaner injection.
What column do you use?

GC Dave


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Eija on Thursday, July 15, 2004 - 04:50 am:

Hi Dave, our ethanol content is 0.1-10 v/v%. We are using 1:40 splitinjection. Our detector(FID) seems to be overloaded. Our sample is 5ml ISTD(0.5%n-butanol)+0.5ml sample. We are using 1%,5% and 10% ethanol-water standards and their ISTD content is 0.5%. Our headspace is 80C for 10min.
We are using capillary colomn, non-polar.

Eija


Top of pagePrevious messageNext messageBottom of pageLink to this message  By GC Dave on Thursday, July 15, 2004 - 06:46 am:

Eija,
When I analyse ethanol in water by headspace the concentrations are much lower (0 - 100ppm) and I get plenty of signal). I think that your concentrations might be too high (5000ppm butanol).
Maybe you need to reduce them to 100-500ppm and maybe increase FID sensitivity?
Perhaps a polar column might help peak shape too. A wax type is often used in this type of analysis.
A DB1/DB5 equivalent may not give you enough resolution.
Regards
GC Dave


Top of pagePrevious messageNext messageBottom of pageLink to this message  By chromatographer1 on Thursday, July 15, 2004 - 09:11 am:

Whoa ! Too much. Too much. Too much.

Lower sample and Istd volumes by a factor of 10 to 100.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By varian on Thursday, July 15, 2004 - 10:25 am:

Try reducing the volume of beer to be analyzed in the sample and use dilute internal standard. Changing to a polar column will improve results.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Consumer Products Guy on Saturday, July 17, 2004 - 11:34 am:

See previous topics (within last 45 days)concerning ethanol assay by GC-FID, this is straightforward.


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