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Thread: Separation of non-polar solvent & water

  1. #1 Separation of non-polar solvent & water 
    New Member
    Join Date
    Aug 2008
    Greetings forum,
    Does anyone happen to know a convenient way to separate a non-polar solvent layer from a water layer when there is a great deal of plant material involved?

    I do extractions of herbs to obtain their alkaloids. Herbs like blue vervain, valarian root, yohimbe root bark, and others. The quickest method is just soak the finely powdered herbs in a solution of water/sodium carbonate. And this make the alkaloids convert to their freebase form because in the plant, they are salts of the alkaloids.

    Since the freebase alkaloids are insoluble in water, but soluble in a non-polar solvent like ethyl ether or odorless mineral spirit, that solvent can then be taken off and the alkaloids are in it.

    There is a hundred ways to do this, and many ways to purify the product, and everyone has their own opinion about how it should be done. But I like to obtain the alkaloids first, then do purification, whereas most people like to purify as they go. I like to make sure I've got the alkaloids first before I do anything to 'em.

    I can elaborate further and give step by step instructions for anyone interested, but I figured I wait until people respond instead of waste time typing it all out right now if nobody here even cares.

    So the quick way is like I said, but the only problem is in order to get the solvent off the water, you need to get all that powdered herb out first because it likes to float right up in the solvent layer. Using a heavy solvent that sinks to the bottom instead also doesn't work because some of the herbal material falls down there too.

    What you end up with is a big mess. But you get total extraction of the alkaloids and highest yield this way. Yes it's much better to simply do a water extraction of the herb in tea bags, then work with that solution, but still you need to filter and go through more work and you loose alkaloids along the way.

    And yes, I could have just filtered the water out of the mush of plant material first, then added the solvent and put on the stirrer for a few hours, then removed the water off the bottom with a separatory funnel, but that's just as much work, and less alkaloid yield. Since these herbs contain very little alkaloids, it's important to get a good yield. By leaving the solvent in the mixture from the start of the process, it ensures you get all of the alkaloids and leave nothing behind in the plant material.

    The way I do it now is to poor the sludge into a funnel with a cotton cloth filter, and each time I have to squeeze the cotton filter to get all the water out of the sludge. This is a very time consuming and agonizing process.

    So I have 3 theories about how to do this:

    METHOD #1.

    I can just put everything in a giant 3 liter separatory funnel, then use a conical flask with vacuum attached to suction the sludge out from the bottom of the separatory flask (it clogs it normally). I can use the same rubber ring that's used with the buchner funnel and that will keep an air tight seal. After most of the sludge is sucked out, I can then add some more alkaline water to the separatory flask, and flip it over a few times until more of the plant material comes out of the solvent layer, and repeat the vacuum.

    Sounds like it might work right?
    But I'm hoping someone here has some crazy wonderful idea of how to get the solvent out from the plant sludge in some easy manner. Nothing on the internet about it yet.

    METHOD #2

    Maybe what I need is some big funnel with a flat disc that comes down and squeeze all the water from the plant material. Does such a thing exist? How to do pharmaceutical companies do large scale extraction of herbs so easily? There has to be some machine in existence already that is used to squeeze the water out of plant material.

    I have this giant 4 liter beaker which works well sometimes to pour off the top layer of solvent from the water since it has a pouring lip. But now with this method of plant sludge, everything pours out together. What I need to do it make a wooden disk exactly the size of the beaker, with holes in it. Then cover it with cloth so the plant material can't get through the holes, the slowly push everything down to the bottom of the beaker, and squeeze out the water and solvent from the plant material. Then I can easily pour of the water/solvent and leave the plant material behind. Some material might come out with the water, but one quick filtration is much easier than 100 very slow filtrations.

    Isn't there some sort of press that does this?

    METHOD #3

    Another method which might work is too attach a vacuum to my conical filtration flask, and then attach a house to the top of the flask and on the hose I can tie a piece of cotton cloth, then just stick that in the beaker with all the sludge, and it should do a vacuum filtration while also transferring the liquid to the conical flask.


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  3. #2  
    New Member
    Join Date
    Aug 2008
    Oh my good lord I can't believe I didn't see this before! I figured it out!

    I just put a cotton cloth pillow case in the 4 liter beaker, then added the plant sludge and water and solvent. Then I just tied the top, and put it in a 5 gallon bucket and squeezed the piss out of it!

    TADA! Instant filtration!

    Now the water and ethyl ether layer separate, and I just pour it back in the 4 liter beaker, and I can carefully pour off the ether layer. Or to be more efficient and get all the solvent, I can use a separatory funnel.

    So there it is! No problem! That literally saved me and entire day of slow filtrations through the funnel method.

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  4. #3  
    Forum Bachelors Degree
    Join Date
    May 2007
    NC USA
    Well done! There is no need for me to suggest vacuum filtration (sucking the liquid through a Buchner funnel).

    For the extraction of alkaloids from large masses of vegetation, I used to use steam distillation. It avoids the use of filtration altogether. But you need the right equipment. So if you think this will be an ongoing process for you, check out steam distillation techniques.

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