math
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Cheap, non-toxic and low-waste plant extractions?
Hi, I'd like to know what are some sensible approaches to extracting and isolate plant matter, while wasting as little as possible and using solvents
which are not that toxic or costly.
I know you're already thinking it depends a lot on the plant and compounds to be extracted, but I imagine it is better to not to be specific about
that, because depending on location, it draws law into the topic, while it should ideally be purely a scientific matter. So, in other words, I don't
know what can be mentioned without crossing that line.
One extraction I'm interested in involves cacti, while the one involves another molecule found on the outer layer of some trees.
Is a Soxhlet extractor (plus associated glassware plus associated heating costs and reflux times) more cost-effective than just using cold extractions
and trying to recover solvents?
In acid/base extractions, I imagine neutralized solvents can be reused for extracting another batch without wasteful distillation, since they don't
need to be pure?
Is Ethyl acetate a cheaper and safer option than Limonene?
Or are there other alternatives?
Thank you
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chempyre235
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As you noted, your choice of solvent depends largely on what you want to extract. However, there are some generalities.
Steam distillation is very common for plant extractions. Many kinds of essential oils are made this way. Cold extractions with ethanol are a route to
making tinctures.
Yes, ethyl acetate is generally much cheaper than limonene. EtOAc is available as "MEK substitute" from virtually every hardware store in the US. It's
sold by the gallon.
Extraction of some sensitive compounds like chlorophyll or DNA require very specialized equipment and procedures.
I've purchased a Soxhlet for the extraction of theobromine from cocoa. I'll have to purchase DCM to selectively remove the alkaloid, but the solvent
is dependent on the solubility of the target substance.
"However beautiful the strategy, you should occasionally look at the results." -Winston Churchill
"I weep at the sight of flaming acetic anhydride." -@Madscientist
"...the elements shall melt with fervent heat..." -2 Peter 3:10
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Radiums Lab
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There is a YT channel called "Tech ingridients", their video "Can I spray it on food" will help you
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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fx-991ex
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Am wondering something which i think could really work.
Years ago i extracted cannabis oil in alcohol and added water 1:1 then washed with non-polar solvent to extract the oil.
The thing is, after adding the water to the oil/alcohol mix we could see the cannabis oil precipitate out of the solution, wondering if just letting
it stand would have worked as an extraction.
That could have been a very short quick and safe way of doing it(without distiling solvent). of course the purity would not be the same but for other
plants it could be a viable option.
[Edited on 25-11-2025 by fx-991ex]
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leau
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Perhaps this document will clarify matters if read 
Attachment: Lecture17 SFC 2023.pdf (1.3MB)
This file has been downloaded 105 times
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clearly_not_atara
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A pretty common technique I've seen used in the literature is to perform an alcohol extract, dry to obtain a residue, and then extract the residue
with a more expensive, selective solvent to obtain desired compounds in higher purity. This allows you to use a cheap solvent to deal with the large
quantity of plant matter, while obtaining the desired selectivity for the most part. Most small molecules of interest dissolve in alcohol with enough
effort.
But in the case of most so-called "precursors", usually steam distillation and np extraction is enough.
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Mateo_swe
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As there are many ways of extracting and what method, what solvent etc differs a lot.
I would look at some of the "free" books (and sometimes not so free but downloadable) sites, there are tons of books about extracting plant matter and
im sure you can find the ones you are intesested in in these books.
There they suggest methods and what chemicals to use for it to work well and the info is easy to find.
Both info how its done industrially and in a small lab setting are often presented.
I would start there if i where interested in such things.
If extracting some common things from sacred cacti there are forums dedicated to such things that share info.
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MrDoctor
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doing extractions totally free of water is probably best whenever possible. any time ive ever tried to process, really anything (mostly for herbal
supplement extracts or concentrates), the biggest PITA is just being able to filter the stuff. theres all sorts of gums, resins, waxes and
exponentially more when you factor in state-changes or complexes that form upon varying degrees of pH change.
but broadly speaking, provided your desired compounds are soluble in ethanol, i would dessicate it, and then extract with reasonably dry ethanol, the
drier the better but, you dont need absolute-ethanol for this, its probably enough just to use silica gel or epsom salts to make sure its at 96-98% or
wherever the azeotrope gets you.
A soxhlet is great but its only really reasonable when like 50g of your material to be extracted from could be considered "a lot", they dont hold much
plant matter, and are also constrained a bit by the fact it has to filter through a plug before it can return, besides also the extracts needing to be
heat stable or not char, since theyll be refluxing constantly. soxhlet is mainly used when material needs a lot of extractions to properly remove the
desired compounds, especially when it has incredibly poor solubility in just about everything.
its basically a magic wand when all the requirements are met though.
steam distillation and, making things work under steam distillation, is probably the way to go imo. you can superheat steam, as well as also run under
vacuum too for whatever reason, if the material doesnt char you can just boil and distill a crude tea and not worry about having a steam generator,
though the faster vapor moves the better things that can be steam distilled, distill.
lastly, ethyl acetate is nice and pleasant and all but i find that its density is a bit problematic for liquid extraction, you need to be mindful that
you get poor seperation when density is too similar between phases, so sometimes you may be forced to add salts to the aqueous layer so its heavier,
for example, but a big one i found was the influence of, what i can only assume was silicates or perhaps calcium sulfate in a specific form, from tap
water. tiny particles that look like a scum layer between phases, preventing complete seperation, EtAc is bad for that, so id recommend using
distilled water a lot or quickly filtering before extraction if that pops up.
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