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Experiments with a Soxhlet

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lethalbacon

Rising Star
This doesn't really fit into a welcome area, so if I end up being promoted I'll likely move it to a more accurate section of the forum. Fair warning, I'm basically using this as my research notes, so it will be very long.

I've done a lot of extractions by hand. I mean a lot. As much as I love the process, there are definitely parts that I find tedious (pipetting 50ML of naphtha out of 2L Erlenmeyer flasks a dozen times, for example). To that end I purchased a Soxhlet extractor setup, along with a basic distillation kit to recover solvents. I am aware that a sonicator is a more time efficient method, but given that I can get a Soxhlet for $50 and a sonicator is 4 figures.

Other well established forum members have discussed procedures and teks for using a Soxhlet in depth, and were my inspiration for this project. I confess that until a month ago I had never even heard of one. As much discussion as there has been however, I have not seen a comprehensive set of experiments with quantitative data. I had to basically dig through different posts and find what looked like the best procedure, so for my own sake any the sake of anyone who reads this and wants to skip the fun parts and get to the most efficient tek possible I'll be doing some trials. As someone with no chemistry background, I will be learning by trial and error, which seems more fun to me anyway. This thread will serve as my way of keeping record of what I have done and want to do.

For reference and for the purpose of testing hypotheses, here are my constants.

500ML Soxhlet extractor. Denatured alcohol (roughly 80 percent ethanol, 20 percent methanol) will be used as the initial solvent, with naphtha as the non-polar solvent. Each trial will be on 50mg of powdered MHRB from the same vendor and in the same batch. White vinegar and NaOH will by the acid and base used, respectively. My reference point will be the most cut and dry extraction I can think of, courtesy of forum member Trickster. Initial solvent will be run over powdered bark until it siphons clear. Extract will be defatted using two naphtha pulls, and acid will then be added to extract to achieve a pH below 4, then basified to above pH of 11. 5 naphtha pulls will be done and freeze precipitated. This will be done three times and the yield will be averaged to give me my baseline for comparison.

Then we'll start changing things one at a time to see how the yield is affected. Things I want to test are below. Not all are directly related to extraction, some things relate to distillation of solvents. I also already know rough answers to many of them, but I want specific numbers. No particular order here, just gonna list them as they come to mind. My primary focus is to maximize yield while minimizing waste.

-How many times can the Soxhlet be loaded on the same batch of initial solvent?
-Can acid be added to initial solvent rather than as a separate step?
-How does defatting in the soxhlet before adding alcohol to extract affect yield, and is it more efficient?
-Can alcohol be distilled off after extracting but before defatting?
-Is defatting actually necessary?
-When distilling naphtha to reduce before freeze precipitating, how much freebase co-distills?

That's all I can think of for now. My sleeping meds are kicking in hard and my brain is going fuzzy though, so I'm sure more will come up and this post will be edited to reflect any additional questions. Experimentation will begin the day the Soxhlet arrives in the mail. I'm very excited.
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Good luck, looking forward to your findings :)

lethalbacon said:
Extract will be defatted using two naphtha pulls, and acid will then be added to extract to achieve a pH below 4, then basified to above pH of 11.
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Why add acid and then base straight away, without doing anything in between? That just neutralizes the acid you've just added.

I think if you're adding any acid at all, it should be added before defatting, to make sure your alks are in salt form and don't get pulled with the naphtha.

It also seems to make more sense to defat before the alcohol pulls, so you don't unnecessary pull fats with your alcohol, reducing the polarity and, consequently, the solvent's capacity to pull the (polar) alk salts.
 
Why add acid and then base straight away, without doing anything in between? That just neutralizes the acid you've just added.
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My thinking is to treat it initially like an acid-base extraction, just using the extract in place of the usual plant soup. I will likely play with times spent in each phase. I imagine that I will find that acid can be added to the alcohol used for the initial extraction, but then I doubt I will be able to recover any alcohol by distillation before doing pulls. Though I suppose that even if I'm distilling off acidic alcohol that can still be reused in that scenario. Adding acid before defatting is a very valid point though, that does make more sense. I was basically trying to remember Trickster's final extraction process, though now that I think about it I may have mixed up her steps. Benzodiazepines sure do help with anxiety that makes it hard to sleep, but they don't make it any easier to remember specific procedures. I will reference the way she did it again, and may very well change the initial procedure.

Running naphtha through the Soxhlet first is very likely the best way to go, but whether or not it will affect the final yield enough to make it worth the extra time that would take is to be determined.
 
lethalbacon said:
As someone with no chemistry background, I will be learning by trial and error, which seems more fun to me anyway.
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Remember, with chemistry there is only so much room for error. Soxhlet extraction is a potentially dangerous procedure if it involves flammable solvents as in your case it indeed does. You will not be able to leave this unattended overnight if the situation where it is being used is in any way domestic. Ethanol or naphtha fumes may escape and build up to cause an explosion hazard. You may also become intoxicated by ethanol fumes if they leak out and - particularly considering you use benzodiazepines - this could also be dangerous for you.

Please make sure your safety procedures are in place before attempting anything involving distillation of flammable intoxicants.
 
Please make sure your safety procedures are in place before attempting anything involving distillation of flammable intoxicants.
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Of course, of course. While I don't have an educational background in chemistry, I am employed in a field involving the use of hazardous and volatile chemicals and materials in an industrial setting. I've learned well the care and consideration required when working with explosives, flammables, and how pressure can build up when you least expect it. Watched a guy blow his arm off when he got careless with a high pressure line he thought was shut off one time, that kinda stuck with me. While it may be a case of famous last words, I do believe that I have a good grasp on the hazards involved. I've rigged up a somewhat unattractive but undoubtedly effective fume hood, ensured that no open flames will be coming anywhere close to the workspace, and all operations will be monitored. As for the benzos, that's a use as prescribed for insomnia type deal, so there won't be any extracting being done while under the influence.

Appreciate the words of caution!
 
There's alread y a few threads in this very forum about soxhlet extractions. Yo uh may be able to eliminate some of the mistakes by taking a gander at those b3fore you start.
 
Squidfayce said:
There's alread y a few threads in this very forum about soxhlet extractions. Yo uh may be able to eliminate some of the mistakes by taking a gander at those b3fore you start.
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I suspect that I've read them, I spent a lot of time looking into this. Most of them had general "this works better than this" statements, and were frequently contradicted by other posts. I want to know exactly how yields are affected by changes in the procedure. Quantitative data and whatnot. To my knowledge, no one has ever said "step 1a reduces yields by 10% but saves 2 hours as opposed to step 1b" or anything of that nature. That's what I want to know.

Plus I just like experimenting.
 
lethalbacon said:
Squidfayce said:
There's alread y a few threads in this very forum about soxhlet extractions. Yo uh may be able to eliminate some of the mistakes by taking a gander at those b3fore you start.
Click to expand...

I suspect that I've read them, I spent a lot of time looking into this. Most of them had general "this works better than this" statements, and were frequently contradicted by other posts. I want to know exactly how yields are affected by changes in the procedure. Quantitative data and whatnot. To my knowledge, no one has ever said "step 1a reduces yields by 10% but saves 2 hours as opposed to step 1b" or anything of that nature. That's what I want to know.

Plus I just like experimenting.
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well, you won't ever find something like that because the answer is dependent on the question and the question is not really relevant..

Understand that the entire point of a soxhlet extractor is the fact that it is a device for quantitative extraction.

That means using a soxhlet will get you the maximum yield possible from a plant material, the cost being that it requires extra work and extra time. So you must judge for yourself if it is worth doing for the particular plant you are extracting.

In the case of DMT and MHRB, this pretty much amounts to a waste of time because out of pure chance it so happens that MHRB is one of the easiest straightforward extractions. (assuming you choose to use reasonable containers/tools).
For example, STB is just about the laziest most straightfowrad method you could possibly use, and it has significant advantages:

It takes no time.
It is incredible simplistic, so good for first timers or people who don't have interest in the workings
MHRB contains no other relevant alkaloids or fats, so the initial crude non polar extracts are already of very high purity. It is relatively scalable (compared to a soxhlet! Not scalable at all)
and the selling point : The overall yield is quantitative, equally exhaustive as if you ran a 24h soxhlet reflux.

Now there are also some disadvantages, but all of these disadvantages can actually be easily worked around. It just seems that most people either don't know about them or they are just getting started and so they follow a 'tek'.

Some of the disadvantages in STB I would say:
People like to use naphtha and freeze precipitaiton. The issue with this is that naphtha is actually quite a poor solvent for DMT (but that is also why it can give you highly pure material directly from the STB, so it's a trade off.) As a consequence, one finds themselves having to use a lot more naphtha then what is necessary, and they have to complete more pulls for an exhaustive extraction (e.g. 5-7 pulls). So it is more time consuming, more wasteful.

In that same vein, scaling starts to become an issue as well. Ending up with large volumes of bark sludge and excessive naphtha. Another disadvantage of STB is that it tends to form emulsions, part of which remain invisible. So a portion of your non-polar solvent remains trapped in the bark sludge, especially if it is not mixed properly, overly shaken.

However, both of those problems can be resolved very easily. Instead of using naphtha, use a better solvent like toluene, xylene, or methylene chloride. This way you only need approx 50mL/per200g of bar, and in my experience, the extraction is exhausted after only 2 pulls, 3 for good measure. Then you just salt out the alkaloids with FASI and the solvent can be re-used. If enough lye is used and some salt is added then emulsions are not an issue either, just don't shake the extraction, mix it gently be patient and let it soak for a night.

There is only one improvement I've found that makes it worthwhile not to do a STB, but it also requires some planning ahead and patience. Soak MHRB in vinegar for a couple weeks, or a month if you like. Don't heat it. Heating only causes problems in filtration and doesn't improve the extraction any further. After a room temp vinegar soak, filtration is very easy and be done in 5 minutes. I like to use a nylon nutmilk bag. Seems like a single soak like this can extract 85-90% of the alkaloids, maybe more.
It makes life easier during the extraction because you don't have to deal with STB sludge, so it speeds up the liquid-liquid extraction process significantly. Instead of waiting overnight and gently rolling and pipetting (no thanks) you can just load the vinegar extract into a separatory funnel, basifiy, and extract with methylene chloride (sinks to the bottom) and be done in minutes. Clean up is easy, no sludge.

Anyway I seem to have rambled on a bit. I don't think there is a single thread that has compiled the data but this is the jist of it. It just so happens that MHRB/ACRB extractions happen to be as simple and convenient as it gets, as extractions go. So there is no need to over complicate it and make more work for no value.

Soxhlet extractors have their time and place, they shine particularly in the case where the desired material contains significant byproducts and fats, and when the desired compounds have particularly poor solubility in all solvents. Imgaine a scenario where you must do a crude alcohol extract, then defat, then purify using column chromatography. In this scenario, the alcohol extract might have you using liters and liters of alcohol, and require you to labor over multiple large size filtrations that are prone to clogging, hell, basically. Soxhlet solves many of these problems, because its mainly set and forget and the volume is kept low as possible, less to distill off in the end. Then for a defat, you can just keep the soxhlet running, switch the solvent to something like hexanes, very convenient.

However in the case of the MHRB, a soxhlet contributes no real value in this extraction. One of the downsides with soxhlets as well is that they do not scale well. Standard size soxhlets (250mL , 500mL) can only really fit a relatively small amount of plant material, depending on the density (50-100g, around). Don't try to overload them either, just a waste of time. Bigger soxhlets (1000mL 2000mL) start to get quite expensive, and still cannot hold very much more plant material. Regular STB extractions on the other hand scale pretty easily. So again, soxhlet just isn't solving you any problems.
 
Mindlusion: would the long vinegar soak pull less oils than boiling, thereby removing the need for defat in the case of ACRB and other oily plant material? (I'm thinking phalaris here)

Also, does the bark have to be powdered, or is shredded good enough?

I find it a bit surprising that such a long soak is needed, wouldn't think a month would make a difference compared to, say, a day. Will definitely try it. And probably with two vinegar soaks to get from that 90% to 99%, and then the vinegar washes can always be reduced.
 
Mindlusion, definitely a lot of valid points. I got my soxhlet from China for $30, it'll be interesting to play around with it and I have other uses as well. If it turns out to not be worth it, no harm done. My main objective is to learn something new and experiment, and from an extraction standpoint reduce the amount of time spent turning bottles over in water baths. Will it be worth it? I don't know, and I won't until I start playing with it. The main advantages I see are efficiency in terms of material waste, simplicity in that once you set it up to run you can monitor it without being actively involved, and the fact that you are dealing with comparatively smaller volumes of liquid. If I can reduce the amount of time spent actively turning bottles over in water baths that would be worth it to me in itself.

Who knows, maybe I'll find that it's a giant waste of time and I'm better off sticking to the classic methods. But the cost to try is negligible, and I'll enjoy the experiment. That's good enough for me.
 
lethalbacon said:
Mindlusion, definitely a lot of valid points. I got my soxhlet from China for $30, it'll be interesting to play around with it and I have other uses as well. If it turns out to not be worth it, no harm done. My main objective is to learn something new and experiment, and from an extraction standpoint reduce the amount of time spent turning bottles over in water baths. Will it be worth it? I don't know, and I won't until I start playing with it. The main advantages I see are efficiency in terms of material waste, simplicity in that once you set it up to run you can monitor it without being actively involved, and the fact that you are dealing with comparatively smaller volumes of liquid. If I can reduce the amount of time spent actively turning bottles over in water baths that would be worth it to me in itself.

Who knows, maybe I'll find that it's a giant waste of time and I'm better off sticking to the classic methods. But the cost to try is negligible, and I'll enjoy the experiment. That's good enough for me.
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I was in exactly the same position as you not too far back. Shiny Soxhlet from china in the cupboard begging to be put to use. After a lot of thought I decided to do the tried and tested and well documented STB for my second MHRB extraction attempt (the first acid to base extraction was a miserable failure with a minuscule yield). The STB exceeded my expectations both in yield and ease.

I would suggest trying something else in the Soxhlet instead and saving the MHRB for a tried and tested process. Perhaps cannabis or even a kitchen herb or spice just to experiment and learn.
 
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