Question/thoughts about solvent extraction technique

[nachoconqueso]

I was thinking that using a 250mL burette and hexane as solvent would perform better than this glass tube with a hole for a butane canister that I have right now. Is it better to bathe the trim in hexane for longer periods of time (say 30 minutes) or do longer baths extract impurities? A burette would work nice for this because I could put a rubber stop on the top and control the extraction a little more. Then run a slow drip into a buchner funnel w/ filter paper. Place that into a sidearm flask and vacuum over a warm water bat. Seems a lot more efficient and lab grade filter paper probably gets a cleaner end product if you get the right ones. Yay? Nay? I don't know guys. Just wondering.

 

[Gray Wolf]

Hexane works well and I've soaked up to 12 hours without picking up any nasties.

 

[G.O. Joe]

Some soak with the minimum amount of solvent in wide-mouth canning jars that are given a shake sometimes, decant, repeat with a fresh solvent soak, then repeat one last time. The 3 portions are united in a fresh jar and frozen 48 hrs, decanted, concentrated, and frozen again.

 

[nachoconqueso]

Thanks for the responses guys.

Hexane works well and I've soaked up to 12 hours without picking up any nasties.

I got another question for you. What is the difference between using a side arm flask with a rubber stopper and a vacuum chamber? Can I still hook up the tried but true Harbor Freight vacuum pump to the flask and it'll work the same?

Basically I'm trying to do this (reduced-pressure evap): http://orgchem.colorado.edu/Technique/Procedures/SolventRemoval/SolventRemoval.html

It's exactly how I remember doing it in my basic organic chemistry lab. So efficient.

 

[Gray Wolf]

It will work the same in thin films, but will be difficult to remove from the flask once the solvent is gone.

 

[G.O. Joe]

I should have added, any kind of sonicating, even a cleaning bath, would speed things up and ensure the best yield. Seriously, been there done that with chromatography columns - it's just more stuff to clean, you'll see.

 

[nachoconqueso]

It will work the same in thin films, but will be difficult to remove from the flask once the solvent is gone.

Yeah I was hoping to corner it and get it hard enough to break away with a scoop.

@ joe: you're probably right

 

[squarepush3r]

Hexane works well and I've soaked up to 12 hours without picking up any nasties.

hi GW, would this be viable to use for extraction?

http://www.ebay.com/itm/n-Hexane-5-...077?pt=LH_DefaultDomain_0&hash=item19d946764d

n-Hexane 5 Gallon Technical Grade Solvent Hexane



The reason being processing a large amount would be difficult costwise with the very expensive Hexane. thoughts? thanks

 

[Gray Wolf]

hi GW, would this be viable to use for extraction?

http://www.ebay.com/itm/n-Hexane-5-...077?pt=LH_DefaultDomain_0&hash=item19d946764d

n-Hexane 5 Gallon Technical Grade Solvent Hexane



The reason being processing a large amount would be difficult costwise with the very expensive Hexane. thoughts? thanks

Technical grades are for general use. We use a reagent grade.

http://www.reagents.com/products/reagents/grades.html

 

[squarepush3r]

Technical grades are for general use. We use a reagent grade.

http://www.reagents.com/products/reagents/grades.html

"Hexane Technical Grade. 50% n-hexane, with a similar content of other hexane structural isomers with that formula."

So if technical grade hexane is just other structural isomers, would it still be just as good for extraction purposes? (Other people besides GW can comment if they have knowledge.) Getting several gallons of reagent grade Hexane is fairly cost prohibitive, so my question is would technical grade be acceptable, or if not why?

 

[Criard]

I was planning on responding to this thread explaining why you would want the reagent grade n-Hex opposed to the technical grade with isomers included; so I started researching n-hex and its isomers...

As it turns out, n-Hexane specifically has been found to have severe neurotoxic effects from chronic exposure but its isomers are not as bad.
http://www.ncbi.nlm.nih.gov/pubmed/7251182
"...n-Hexane, 2-methylpentane, 3-methylpentane and methylcyclopentane were diluted with olive oil and orally administered daily for eight weeks...The results revealed that the neurotoxicity of the three chemicals was not so severe as that of n-hexane and were in the order of n-hexane greater than methylcyclopentane greater than or equal to 2-methylpentane divided by 3-methylpentane."

Apparently these neurological issues come not from the hexane itself but from a metabolite, "Hexane-2,5-dione". My researching also showed that 3-methylpentane (isohexane) is being considered as a replacement solvent for n-hexane in the food oil industry and that n-heptane is already starting to replace n-hexane in pharmaceutical processes because of this reason.

So...why exactly do you want reagent grade n-hexane? I found that the 3-methylpentane is pretty much unobtainable right now at least for any reasonable amount of money, and that pentane costs about twice as much as hexane. But are there any specific chemical reasons that you use hexane over pentane?

 

[Gray Wolf]

"Hexane Technical Grade. 50% n-hexane, with a similar content of other hexane structural isomers with that formula."

So if technical grade hexane is just other structural isomers, would it still be just as good for extraction purposes? (Other people besides GW can comment if they have knowledge.) Getting several gallons of reagent grade Hexane is fairly cost prohibitive, so my question is would technical grade be acceptable, or if not why?

Tongue in cheek answer. It depends on what those other structural isomers were.

None of the alkanes in the neighbor hood of Hexane are anymore toxic than Hexane, but some of the alkenes are considered carcinogenic.

We use the HPLC reagent grade because it is free of enough other contaminants to not add additional peaks to a HPLC.

 

[Gray Wolf]

I was planning on responding to this thread explaining why you would want the reagent grade n-Hex opposed to the technical grade with isomers included; so I started researching n-hex and its isomers...

As it turns out, n-Hexane specifically has been found to have severe neurotoxic effects from chronic exposure but its isomers are not as bad.
http://www.ncbi.nlm.nih.gov/pubmed/7251182
"...n-Hexane, 2-methylpentane, 3-methylpentane and methylcyclopentane were diluted with olive oil and orally administered daily for eight weeks...The results revealed that the neurotoxicity of the three chemicals was not so severe as that of n-hexane and were in the order of n-hexane greater than methylcyclopentane greater than or equal to 2-methylpentane divided by 3-methylpentane."

Apparently these neurological issues come not from the hexane itself but from a metabolite, "Hexane-2,5-dione". My researching also showed that 3-methylpentane (isohexane) is being considered as a replacement solvent for n-hexane in the food oil industry and that n-heptane is already starting to replace n-hexane in pharmaceutical processes because of this reason.

So...why exactly do you want reagent grade n-hexane? I found that the 3-methylpentane is pretty much unobtainable right now at least for any reasonable amount of money, and that pentane costs about twice as much as hexane. But are there any specific chemical reasons that you use hexane over pentane?

No, we actually like Pentane better, because it is easier to purge, but it is more expensive. It will also absorb more water than Hexane, but not enough more to make an appreciable difference when extracting.

Mostly we don't normally extract with either one, but use them for alchemy. They both make a nice extraction, but it is cheaper and faster to use a recycling butane system, and the quality is also excellent, so neither Pentane or Hexane are our heavy movers.

Don't like Heptane, because it is even harder to purge afterwards. Hexane works better for alchemy than Pentane because it will absorb less water.