Dr. Funkenstein
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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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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!
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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JohnWW
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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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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.
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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crazyboy
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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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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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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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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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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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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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Chloroform. High specificity.
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