I am curious why I hear no mention of extracting with this solvent in this industry.

  • cheap
  • efficient (possibly as good as chloroform)
  • non-flammable
  • easy to get
  • minimal viscosity changes when chilled (-50C)
  • easy to work with provided there is decent ventilation

If the extraction goal is “crude”, which will be subsequently finished, the issue of residual halogens is irrelevant.

Can someone give me a rational explanation?
Is this strictly a matter of environmental politics surrounding the use of any chlorinated solvent?

I would really appreciate any insights the community might have.

I use dichloromethane from time to time. One of my IG videos shows how selective it is in disolving some of the waxes but leaving others. It is also heavier than aqueous layer so when used for say an liquid to liquid extraction this could be leveraged in a counter current fashion pretty well using sep funnels.

There are lots of good reasons to use any particular solvent but the reason I have for not using it much and no intention of reordering is the stink. I hate the stink of it much more than any other solvent I use.


Beaker, sounds like you have experience with the solvent. I do not find the smell objectionable. In any case, we are largely discussing closed loop systems in this thread, so the operator should have minimal exposure to the small, especially if one has decent industrial quality ventilation in place.

Would you elaborate on the selectivity of the lipid extraction?
No comment about why it is not more prevalent?

For those of us that operate in state licensed facilities we are often very limited to a short list of solvents. Our state licensing division wouldn’t even know how to spell dichloromethane let alone allow it’s use. Hexane is a great solvent too but also not allowed for use in licensed facilities in CO.

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The state regulators used the FDA Q3C residual standards as a basis, dichloromethane (600ppm) and hexane (290ppm) have lower allowances than even methanol (3,000ppm.)

The state regs suck, I started thread just to say so…

FDA Q3C residual standards,

Dichlormethane at PubChem,


Here is the thread showing the solubility test.

I don’t know why others might not choose the stuff except it would require gearing up in a whole new way. For instance, right now all the seals, gaskets, and o-rings and such in these systems are designed for ethanol now generally. If you needed to use dichloromethane or any other less polar solvent then most certainly seals would be a problem. I toasted a sublimator seal pretty fast by exposing it to solvents like this. The theoretical of course takes a back seat to the practical. The practical matter here is the availabiliy of systems able to be licensed for hydrocarbon extraction. In Oregon it is banned. So any likely manufacturer would be locked out of at least one state and likely most states. This makes it unattractive to dump R&D money into a process.

The polarity value given to it by Reichardt is 0.309, which is between methyl iso-butyl ketone (MIBK) at 0.269 and ethyl formate at 0.315. Here’s my personal list of solvents and their polarities from non-polar to polar for comparison,

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600ppm should be a no brainer to achieve, possibly even in a rotovap. DCM evaporates easily, with very little energy input, boiling point of 37C, a tenth of what ethanol takes.
Viton o-rings/seals work just fine. I would assume all current extraction equipment would be using viton.
Any ethanol extraction process gear should work just fine. I get that there is a lack of familiarity with this solvent, but the extraction of bulk crude should be as efficient as possible, and so far, CLS seems the most efficient with the drawback of C1D1 flammability concerns. Painful.
Nice pic of the wax. Not sure how it differs from any other solvent. I would think the slight polarity would favour extraction of terps and CBD, a good thing, no?
According to Q3C, its a class 2 solvent NOT TO BE confused with dichloroethane, a dangerous class 1.
Banned in Oregon? Why? It is clearly listed in the Oregon Admin Rule 437, Table Z-2, with occupational exposure limits at 100, 200, and 300 ppm.

So…still don’t have a science answer. Hope someone out there has an apolitical rationale. This solvent was at one time the de-facto standard for decaffeination and I can not seem to find a valid reason its is not in use in the extraction of cannabinoids. It appears to be a better choice than anything out there except butane.

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Obtain a viton o-ring and place it into dichloromethane, hexane, acetone, ethyl acetate or likely all alkanes. It takes very little time for the O ring to swell beyond usefulness. There will be a tolerance to a degree for a period of time but I very quickly toasted an o-ring by clamping shut my sublimator with o ring installed with some ethyl acetate in it. It swelled at least 15% when I came back overnight and unclamped it.

I understand this sort of thing can be mitigated but the other clue is to take a kimwipe and soak it in the solvent you want. Then wipe hard around an o-ring. If it is among those listed you will see viton color come off on the kimwipe. Irregardless of what the charts might say about chemical resistance try this experiment and you will see that viton does indeed become unusable with sufficient exposure. I do like your idea but I do question obviously whether Viton is impervious to the less polar solvents based on what I have seen.

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Ah, the dreaded solvent resistance test. We agree wrt viton resistance to non-polar solvents in general. However, the use of DCM puts very little stress on the sealing arrangement in that there is no high pressure involved in the extraction. I say again, DCM at one point was the predominant extraction solvent in industrial use. Clearly, there are ways around the solvent resistance problem.
My objective is to find a cheap, easy, safe way to extract target compounds. All the hydrocarbons and EtOH have flammability issues. CO2 is expensive and requires extensive de-waxing.
Why is DCM not in commercial use?
The legislation for residuals was raised to ridiculous levels in the Jan 2017 regulation updates. Well above what I would consider safe. Clearly, the industry is more conservative about residual solvent concentration that the FDA is.

dcm will pick up a heck of alot more waxes compared to etoh, even when chilled. Most large scale processers will try to avoid winterizing to save on time. They are able to circumvent winterization because waxes are mostly insoluble in chilled etoh; therefore, a filteration to remove particles followed by evaporation is an efficent way to process.

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The FDA isn’t making recommendations for folks huffing the stuff. So being more conservative than them strikes me a great idea.

Or maybe it’s just not Good for you…

Classified as a neurotoxin, dichloromethane has been proven to cause damage to the brain and central nervous system (CNS). The Environmental Protection Agency (EPA) has classified it as a probable human carcinogen since high levels of exposure to the chemical has been proven to cause liver and lung cancer in animals

Latest research shows we picked up the ADH4 allele some10million years ago, so ethanol has been on our list of “usable” for a wee bit longer.


Thank you Soxhlet. You are the first to step up and give me a rational reason for not using DCM. I am assuming you have empirical experience with cold DCM extraction and KNOW that DCM will extract more lipids?

watch how the dcm interacts with the waxes vs the alcohols.

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I provided the PubChem link up front, under toxicity it states the concerns of the scientific community,



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I believe the operative phrase here is “at one point”. If you look closer you’ll find that DCM is no longer the predominant extraction solvent because we now know better…and have better solutions.

The Romans ran lead water pipes for a long time. it seemed like a great idea. we eventually figured out why it wasn’t. Folks in Flint are wondering why we kept using it long after we discovered there were issues…


The Bligh and Dyer or Folch procedures for the extraction and separation of lipids from plants, microorganisms and otherbiological meterial using chloroform/methanol/water have been used tens of thousands of times and are “gold standards” for the analysis of extracted lipids.

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I’ve extracted thca via washes with dcm. It’s pretty cool. Sorta dangerous to use. But very cool.

TCM and DCM are very common for analytical processes but less so for preparative ones. They’re like anything: they can be used safely but usually the extra measures add expense that makes other options more attractive. For instance, TCM supposedly allows for a good isocratic chromatography method, but most labs would rather deal with solvent recycling than handling halocarbons