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Author: Subject: Question about plant oil extraction using ethanol.
Dr. Funkenstein
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[*] posted on 22-7-2009 at 23:06
Question about plant oil extraction using ethanol.


Hey all,

After a good bit of lurking I decided to post a quick question I had.

Not sure the exact rules of this board. If I violate, please pm me and I will happily change what needs changing.

I have some herbaceous plant extract(oil based) that has been stripped from raw plant material using ethanol as a solvent. Usually the ethanol is distilled off and recycled to provide a thick, viscous, oily extract of the plant.

I only have a small hand vacuum pump and its a real PITA to sit and watch a few gallons distill while pumping every 5 min. The final evap is done in a evap dish or watchglass. The solvent/oil mix is dripped into the evap tray in small quantities until dry...

Soooo, long story short, I was wondering if this type of procedure can be simplified by extracting the oil out of the ethanol into another solvent of lesser volume. It would be ideal if the oil could them be transferred back into ethanol since I use food grade everclear for this project....

Or I could just turn the oil bath up a wee bit and not use the vacuum pump and distill @ 76C since that temp isn't destructive. I figured it takes long enough with the pump, but don't know how long it would take without the pump....might have to find out tomorrow :)

Thanks

Dr. Funk
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Nicodem
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[*] posted on 22-7-2009 at 23:32


I don't know what you mean by "oil", but if you are extracting lipids then you are using the wrong solvent. Ethanol will extract all kind of crap as well. You need to extract with petroleum ether if you want the lipid fraction of the plant material.

And buy yourself an aspirator!




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JohnWW
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[*] posted on 23-7-2009 at 06:47


That is right, Nicodem. The solvent to be used to extract various natural products from plant materials depends on the nature of what is desired to be extracted, particularly the polarity and molecular weight. Alcohols (ethanol, methanol, isopropanol, usually) are used to extract fairly highly polar and low molecular weight substances. Petroleum ether, and also other hydrocarbons such as toluene, benzene, hexane, cyclohexane, etc., would be used for mainly non-polar natural products of fairly high molecular weight. Other possible solvents are ethers such as diethyl ether, THF, dioxan, used for substances somewhat more polar than for which hydrocarbon solvents would be used; and ketones such as acetone and diethyl ketone and methyl isobutyl ketone which would be aprotic alternatives to alcohols. Pyridine is a possibility for substances that form complexes with it.

Water would be used only to dissolve the most polar substances of low molecular weight. Another alternative is steam distillation (a scale-up of Soxhlet extraction), used to extract volatile essential oils such as terpenes on a commercial scale. The same choices of solvents would apply to separations of such substances by chromatography, particularly paper, thin-layer, and packed-column chromatography.
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starman
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[*] posted on 23-7-2009 at 10:07


Typically when an alcohol has been used for the initial extract it is diluted with water then taken up in something like petroleum ether(Not that hard to source or fractionate it yourself).Or far more simply use the ether for the intial extract as Nicodem posted.Given more on the specific compound desired isolated(even in general terms) members can be of more assistance.



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crazyboy
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[*] posted on 23-7-2009 at 15:12


Quote: Originally posted by starman  
Given more on the specific compound desired isolated(even in general terms) members can be of more assistance.


I think he is trying to extract THC.




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JohnWW
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[*] posted on 23-7-2009 at 18:44


THC and other cannabinoids? Those are higher molecular weight alcohols (and possibly phenols). Isopropanol is most commonly used for that solvent extraction. Ethanol could be used, but is costly because of the high excise duty on it. Methylated spirits, which is 90% ethanol adulterated with substances like methanol, pyridine, and sucrose acetate to render it unpalatable, could possibly be used, if one could be sure that the adulterants were not a problem.
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donlaszlow
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[*] posted on 4-8-2009 at 09:15


plus THC is illegal! But if your goal is i.e. rose oil, there are several methods that can even be used at home, yielding a good quality oil. No solvents are required. And rose oil is expensive, and you need a lot of petals, but it's worth a try, because nothing compares to it.
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ProChem
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[*] posted on 4-8-2009 at 09:34


my college lab extracted caffeine from tea with mehtylene chloride and at work we extracted ambrain from gum labdanum using hexane. The same gum labdanum gives labdanum absolute using ethanol. some alkaloids have functional groups that act like acids or bases so some solvents can be modified using acids or bases.
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Rich_Insane
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[*] posted on 4-8-2009 at 09:44


If it is THC you would like to extract, there is a thread on doing an Isopropanol wash then something else on Zoklet. Check it out.

It all depends on polarity, structure, functional groups, etc. If you can tell me the molecule(s) you wish to obtain, I can look it up in the Merck Index for you. It's quite a handy tool to have.

I would not use ethanol really. Maybe I would do an ethanol wash, determine where the molecule is, do a nonpolar wash with hexane or naphtha, determine where the molecule is, then either do a A/B extraction or just wash again with a highly volatile solvent, evaporate it off and obtain either your oil or your crystal. Ethanol brings out chlorophyll, and it may bring out all kinds of odd stuff like sugars, salts, etc.

If your molecule is similar to something like say, cocaine, which can be made hydrochloride and sulfate, etc. I'd say you should do an Acid-Base (A/B) extraction afterwards to get a purer extract.

I do know that in Eastern Europe there is methylated alcohol without methanol, just a bitterant and a dye. You could distill out the ethanol which is a far lower MW. I would avoid ethanol as a primary solvent though, and rather as a washing substance.
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gungfucuddler
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[*] posted on 21-11-2010 at 17:35


If you are asking a purely theoretical question about a procedure to extract the oils out of a certain plant in the Cannabaceae family then I offer a procedure.

After an ethanol extraction one could do a polar/non polar extraction using benzene or dichloromethane or some other non polar solvent with a very low boiling point and then simply rotovape or hot water bath evaporate the solvent to be left with only the desired oil. This procedure would also purify the oil because the non polar solvent will not extract the polar compounds in the ethanol such as sugars, salts, chlorophyll et cetera. Which would produce a smaller amount of more concentrated product. Since the procedure you expressed interest in desires a final product that is dissolved in ethyl alcohol, the final volume of the extracted oil will not matter so much.

Science is fun, enjoy it, be safe.

My disclaimer: I believe it is our ethical responsibility as scientists to not take actions that we know will be destructive to the world in which we live. I feel evaporating off solvents such as Benzene and Dichloromethane into the atmosphere would fall under that category. Always recollect your solvents the best you can. I merely propose the idea that one could evaporate the solvent in a hot water bath because it can be done, not because it should be done.
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JustMe
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[*] posted on 21-11-2010 at 18:28


Quote: Originally posted by crazyboy  
Quote: Originally posted by starman  
Given more on the specific compound desired isolated(even in general terms) members can be of more assistance.


I think he is trying to extract THC.


Chloroform. High specificity.
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