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O2 in jet fuel
Posted: Mon Apr 20, 2009 1:06 am
by DTM
Greetings. I'm trying to determine oxygen content in jet fuel using a Carboxen column with an TCD (sorry I'm stuck with packed column technology). Determining the O2 content is somewhat straight forward but I'm concerned what effect the aliphatics, aromatics, and additives from the jet fuel might have on my column.
Has any body had any experience with this type of analysis before or can recommend some alternatives?
Regards,
DTM
Posted: Mon Apr 20, 2009 8:00 pm
by larkl
You could add a valve and backflush or strip the 'heavies' out of the sample, if you're worried about it. I don't think it's much to be concerned about, but I'm not that up on the packed phases.
Posted: Tue Apr 21, 2009 3:29 pm
by chromatographer1
Large molecular weight hydrocarbons may reside on the Carboxen and eventually plug the pores of the packing which will end the separation of O2 you seek.
A backflush column is recommended.
A combination of carbowax 20M on teflon and carbowax 20M on a white diatomaceous support would be a good recommendation for a backflush column (1 meter should be enough, 0.5m of each support with the teflon on the inlet side). Remember to use glass lined or fused siica lined SS tubing with internalized SS screens to contain the packing loss caused by the reversal of carrier flow during the backflush. This will increase the time before a valve repair will be needed.
Protect your Carboxen column and it should give you many months of service before replacement is required.
best wishes,
Rodney George
consultant
O2 in jet fuel
Posted: Thu Apr 23, 2009 5:21 pm
by DTM
Rod: Greetings. Yes the original paper that I am using suggested something similar but I am limited in my options using a packed injector (no split). Plus I'm not sure where I would place the valve for the backflush, where it exits the TCD or in the oven at the end of the column train.
Regards,
Dan
Posted: Sat Apr 25, 2009 12:19 am
by chromatographer1
I am curious about your sample introduction.
If you are not using a valve to inject the jet fuel, how are you injecting and how much?
But a simple 6 port rotor or diaphram valve will allow you to use a backflush.
You may wish to review on Valco web site or other valve provider such as Supelco for a simple solution. These vendors can assist you in modifying your GC.
You should backflush your sample and not permit jet fuel to elute through a Carboxen packed column.
I hope you take my advice and seek proper vendor assistance.
best wishes,
Rodney George
consultant