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Wax analysis
Posted: Mon Sep 06, 2010 1:37 pm
by Rouan
Hi All,
Need some info, not sales talk. I am trying to optimize a high temp GC method for Wax analysis. 6890 with PTV injector. Currently getting good responses upto C40. There after response drops significantly. Has anybody tried to do higher carbon numbers? Cool-on column injections? Which PTV liner works best.
Thanks.
Rouan
Posted: Tue Sep 07, 2010 11:26 pm
by mbicking
First. do you know if your wax sample has molecules larger than C40?
About C40 I think you are at the limit of volatility for the hydrocarbons at the normal maximum temperature for the column and GC. What are your conditions? You should be using a short column with a very thin film.
Look up applications for simulated distillation, where the analysis goes up to about C100. I know both Restek and Agilent have columns that are designed for these higher temperatures.
Posted: Wed Sep 08, 2010 2:33 am
by Consumer Products Guy
For candles, we usually didn't see anything larger than C35. We used traditional split inlet and metal capillary column designed for high-temperature use.
Posted: Wed Sep 08, 2010 8:29 am
by CE Instruments
We used traditional split inlet
Traditional split injection will not transfer anything above C40 and will be discriminating badly by C35
Thermo demonstated Polywax analysis to beyond C100 with cold on column and managed to do similar with their PTV. I have also seen similar good results from the Optik injector. With PTV the key to sucess is sufficient heat transfer to drive the sample from the injector into the column. Having the right column helps too
Posted: Wed Sep 08, 2010 12:32 pm
by Consumer Products Guy
Like I said: our candles and our competitors' rarely had over C35. We used C28 by itself as the identifier.
Most candles were paraffins, some were hydrogenated triglycerides, a few were combinations.