[lockjaw]

Hello,

I have not been able to find the answer through much searching.

Is it possible to use TLC to test for presence of butane in a resinious extract?  I was looking into mobile phase, but due to butane low bp (-0.5'C) I am not sure what route to take.

I am also interested in quantitative results with TLC (using JustTLC), however, I am unsure where I could order some kind of n-butane standard (if possible in first place).

Could anyone please offer me some clarity or guidance?

I also wish to test for presence of ~95% ethanol azeotrope in extract with TLC.

Thank you very much.

[stewie griffin]

Since butane is going to be a gas at room temp I don't see how you could possibly do TLC on it. I would say there's no way you can use TLC to detect butane.
Why not try Gas chromatography though? Inject a standard sample of butane first so you know the retention time and then you can compare your samples. Furthermore, you should be able (in theory at least) to make a standard calibration curve so that you can get quantitative info.

[lockjaw]

Hello,

Thanks for your response.  I am trying to develop a method where one does not need GC, etc.

I was considering trying carrying out butane TLC detection in a cold environ.   A walk in freezer/fridge or large cold cooler.   And to dry plates I was thinking of vacuum desiccator in cold environ if needed.

That method seems like it might work(?).

If that method will work I need to find solvent for the resinious extract, mobile phase, and hopefully visualization reagent.

Thanks

[MOTOBALL]

Listen to Stewie Griffin---there is NO WAY to do this by TLC. 

GC is the ONLY method.

Motoball

[lockjaw]

OK,

My last dumb question today...

Because I am using ethanol as co-solvent (higher bp and density than butane) I think I could assume a lack of ethanol also means a lack of butane.  Thus my question becomes, can/how could one detect ethanol in a resinious extract? 

I am unsure what extract solvent, mobile phase and hopefully visualization reagent to use (if possible in the first place).  I am off to do more searching/research on ethanol detection with TLC.

I know GC will work, but I want to try and find a method to use TLC, chroma paper, etc.

Thanks to both of you.

[lockjaw]

Hmmm,

As I am looking to detect ethanol I wonder if the following would work well.  Using ones sniffer (nose) might be a good option for a simple test.  But I would far prefer to use TLC.  Either way I would need to use a solvent for the extract so I could add the salts:

http://www.physicsforums.com/showthread.php?t=105655&page=2
"Potassium permanganate or potassium dichromate can be used to oxidize alcohols to their carboxylic acids which can be identified by their foul smells."

[Markov]

Sorry, TLC won't work for ethanol either.

Also:

Because I am using ethanol as co-solvent (higher bp and density than butane) I think I could assume a lack of ethanol also means a lack of butane

The above assumption sounds like very thin ice.

If you would explain the basic concepts of the study you are planning, you are far more likely to some useful help here.

Good luck and best regards

[lockjaw]

Hello,

Thanks for your input.  But I am pretty positive what I suggest is fine; that is an absence of ethanol = absence of butane.

Essentially what I am doing is extracting from plant matter with butane.  Once I boil off most all butane (could be some 'stuck' in matrix) the extract is resinious.  I then redissolve the resinious extract with the co-solvent of ~95% food grade ethanol azeotrope.

Once the extract is dissolved into ethanol the compound goes into a microcentrifuge filter tube and then into a  freezer (-18'C) for 24 hours to precipitate butane.  Then the tubes are placed into microcentrifuge and run for 15 minutes.  The microcentrifuge will further precipitate butane and the filter (0.2 micron) will collect precipitates.

After microcentrifuge the compound is poured into a vacuum chamber (12.5" bell jar).  An aspirator (using water) is hooked up to a recirculating water system.  The partial vacuum (55-70 mm Hg) will drop bp of ethanol to room temp at normal air pressure.  Partial vacuum is run for 2-4 hours.  The density of ethanol is a good deal more dense than butane, and ethanol bp is a good deal higher than that of butane.  Thus the butane will head to the surface of ethanol so it will boil off first.  Then the ethanol will boil off.

After the drying I want to test the extract for presence of butane, however, as mentioned that requires GC, etc.  Thus I want to look into detecting ethanol as the absence of ethanol should mean absence of butane.

Do you see any glaring flaws in my thought process?  I do not.

Thanks

[lockjaw]

Hmmm,

This method seems like its something to check out.  I am going to read the following full papers today, however, I am currently unfamiliar with fluorous phase chemistry[1].  I hope this method could be a viable and inexpensive possibility for at home detection of ethanol.  See:

"A copper(II)-based multiphasic fluorous colorimetric ethanol assay"
⁠author(s): Mounir El Bakkari, Raymond Luguya, Rosenildo Correa da Costa and Jean-Marc Vincent
New J. Chem., 2008, 32, 193


"Hot article: Breaking news, ethanol detected in Bordeaux"
http://www.rsc.org/Publishing/Journals/nj/Hotarticles/B716544G_Vincent.asp

To avoid water competition in indicator-displacement assays (IDA), encapsulation of the receptor into a polymer film or behind a water-impermeable polymeric membrane are methods that have been generally investigated. The new results obtained by Jean-Marc Vincent and his colleagues from the Institut des Sciences Moléculaires in Bordeaux, France, show that the use of a fluorous phase should now be considered as a possible alternative.

Vincent's group first reported in 2002 preliminary results on reversible phase-switching of pyridyl-tagged compounds between hydrocarbon and perfluorocarbon (PFC) phases. The growing interest on ethanol as an energy source naturally attracted the Bordeaux team's attention, and the French chemists hypothesised that their methodology could be employed to develop a "simple" colorimetric assay for ethanol detection and/or titration. In this work Vincent et al. clearly demonstrated that compartmentalization of a chemosensing ensemble in a PFC may allow its use in conjunction with an aqueous phase (containing the analyte) without interference due to interactions with water (Scheme 1). 

The simple fact that ethanol can be selectively detected in a vast amount of water, whilst ethanol and water should exhibit similar coordinating properties towards copper(II) ions, is a significant result.   

A major drawback of the present ethanol assay remains in the use of chloroform, a toxic chlorinated solvent as a detection phase. To counter this problem, the authors are now employing their efforts to develop water-soluble indicators.

The "FluoroFlash® TLC Plates" sounds interesting:
http://www.fluorous.com/groups/TLC-9.html


Another paper which seems worth reading:
"Separations with Fluorous Silica Gel and Related Materials"
Author(s): Gladysz, J. A.; Curran, D. P.; Horvath, I. T. Eds. Wiley-VCH
Handbook of Fluorous Chemistry, 2004,  pp101-155.




[1] "Fluorous phase chemistry: a new industrial technology"
Author(s): Adrian P. Dobbs and Meriel R. Kimberleyb
Journal of Fluorine Chemistry
Volume 118, Issues 1-2, 1 December 2002, Pages 3-17



Any opinions?

[lockjaw]

This may work, input is more than welcome:

Redissolve final resinious extract with solvent having a bp much different than ethanol.  Bp of ethanol is 78.15'C.  None of the other chemicals in the extract have a bp of 78-79'C (AFAIK).  Thus if I heat the compound to 78.5'C and something boils ethanol is still present.  Make sense?  If so I just need to figure out what solvent to use.

If boiling does happen at 78.5'C then one could assume there might be ethanol present.  At that point I would use GC/MS for quantitation. 

If this method is valid it would be a good "quick and dirty" test for presence of ethanol...

[Markov]

But I am pretty positive what I suggest is fine; that is an absence of ethanol = absence of butane.

Yes, that is probably correct.

Do you see any glaring flaws in my thought process?  I do not.

1) Boiling and freezing of mixtures is rather different than for pure compounds.
2) To get rid of, or determine residual solvents is rather different than removing bulk content from a solution.

You may want to ask yourself how much butane does the resin really retain? Is it really so bad if there are trace amounts left?