Jump to content
The Corroboree
Yeti101

Electrolysis/Electrocoagulation of Alkaloids?

Recommended Posts

Was going over some old blog notes from years ago and saw a post from 2008:

If you run current through a solution (aqueous obviously) of an alkaloid salt, will the positive ions, in this case the alkaloid, migrate to the cathode? I think they would. If it forms crystals in its freebase form, then it should literally grow on that electrode! Of course in a dirty solution there would be all sorts of other crud attracted. I don't expect that you can throw a couple of wires into some tea and pull them out with glistening crystals attached a few hours later. But I do wonder if it is worth a try. Surely this is something other people have tried before?


As it turns out, other people had thought of this.

Vdoviko, E. A., Pokhmelkina, S. A., & Petrenko, V. V. (1972). The electrochemical extraction of alkaloids of the tropane group from plant raw material. Chemistry of Natural Compounds, 8(3), 327-329. http://link.springer.com/article/10.1007/BF00563741
and
Phutthawong, N., Jumpatong, K., Chairungsi, N., Wangkarn, S., & Buddhasukh, D. (2007). Application of Electrocoagulation to the Isolation of Alkaloids. Chiang Mai J. Sci, 34(1), 127-133. (attached)
I'm interested to hear what some of our more capable chemists thing of these sort of approaches - I know I don't have the expertise to make sense of it, (but still find the ideas interesting).
Edit: actually attached the file, finally.

10-11-11-e49b8.pdf

Edited by Yeti101
  • Like 1

Share this post


Link to post
Share on other sites

I witnessed a similar conversation a few months back between a chem student and electrical engineer and they seemed to have fun toying with the idea. I'd love to hear what others have to say! Thanks for thinking of this thread yeti.

Edit: I think they were talking about electricity as the catalyst so maybe slightly different concept

Edited by theuserformallyknownasd00d

Share this post


Link to post
Share on other sites

Maybe - as it is the two papers I mentioned are doing slightly different things. I actually found a patent from 1926 https://www.google.com/patents/US1815302 (well worth a read) that describes what I was thinking of. Add some modern semi-permeable membranes, and bam - alkaloids!

Edited by Yeti101

Share this post


Link to post
Share on other sites

I'm not sure about that. I play with electro-chemistry etc. myself. for metals and other such works. Any electrical current will oxidize at one terminal and reduce at the other. Comes down to potential and other factors. Different electrode materials will have differing values and effects on these types of experiments. I'd imagine magnetism would have similar effects?

why not just use centrifugal force? or column work? I could try it for you if you like? I have platinum / pyrex electrodes and others. along with porous cells. If it's legal work let me know and i will try it for ya =) I'd imagine such would take very small voltages.

  • Like 1

Share this post


Link to post
Share on other sites

Indeed, ghostly, it is probably not that simple. The fact that there are so many other techniques suggests that the electro route may not be straightforward as that 1920's inventor envisaged. That said, his description (in the patent) of extracting crystal quinine from cinchona bark sounds impressive, as does his list of suggested applications for his invention.
These days, in an ideal situation, you would probably not try this. But not everything is an ideal situation.

Share this post


Link to post
Share on other sites

If you run current through a solution (aqueous obviously) of an alkaloid salt, will the positive ions, in this case the alkaloid, migrate to the cathode? I think they would. If it forms crystals in its freebase form, then it should literally grow on that electrode! Of course in a dirty solution there would be all sorts of other crud attracted. I don't expect that you can throw a couple of wires into some tea and pull them out with glistening crystals attached a few hours later.

Interesting! I dunno about "capable chemist", I'm probably more in the "half-assed dilettante dropout" category, but I had some thoughts. That first paper is behind a paywall, but I read the second one and they seem to actually be using the idea around the other way to what you describe. So instead of attracting the desired alkaloids, the electrolysis is "coagulating" out the crud like tannins, leaving a somewhat-cleaner solution of mixed alkaloids, no membrane required as there is only one compartment:

...it appears that, like glycoside, the amine function in the alkaloid seems to be unreactive to coagulation under the electrochemical condition used in our operation. EC in this case will then serve to clear up the undesirable impurities, e.g. tannins and pigments, by coagulating them out. What remains in the solution is therefore a purer alkaloid fraction, which can be easily separated. In most cases, this is done simply by evaporating out the solvent from the filtrate obtained after filtering out the coagulated impurities.

The residual crude alkaloid, still containing the salt added as supporting electrolyte, is dissolved in a little nonaqueous solvent, usually ethanol or acetone, to rid it of salt in the final step.

To an extent this concept is already used in biochemistry - electrochromatography & gel electrophoresis - but I've never heard of its use for smaller, simpler molecules. Curiouser & curiouser. Mr Hogstad's patent app makes it sound so effective - in one experiment he was using as his filter, not any kind of complex membrane, but plain canvas! On a side-note, congratulations to that man for writing hands-down the most readable patent application I have ever encountered - nice work Hogstad! He points out that developing practical methods for each material would involve a lot of trial-and-error, and notes the importance of pH, voltage, and type of membrane(s) used. The metal used for the electrodes may be important too, he describes some options...

A cathode of iron, copper, or other metal may be used in place of the graphite cathode, provided it is not attacked by the cations; but because of Ithe corrosive action of anions commonly encountered,.such as chlorides or sulphates, graphite, platinum, or other-material highly resistant to corrosion must be used as the anode.

...and the 2006 paper (Phutthawong et al) goes into the chemistry of that a bit:

The process comprises an electrolysis setup (Figure 1), normally with aluminium or iron plates being used as both electrodes to generate in situ such species as Al3+, Fe2+, Fe3+, OH-, Al(OH) , Fe(OH) , etc., which are capable of selectively coagulating some particles soluble or suspended in the electrolysed solution

I know that platinum & palladium electrodes (& possibly other metals like silver?) can be used as catalysts in certain reactions, but I'm not sure if that would be a factor here. Probably not.

I think the best place to start would be trying to replicate one of these published experiments (eg. caffeine from tea leaves). If you can get that working, then maybe try moving on to other materials.

I suspect that if this works, it will turn out to be a field something like thin-layer chromatography, where the selection of your electrode-metals, pH, salinity & so forth is vital to an effective extraction/purification. But if it means that extractions could be run cleanly from solar power or something, with the only solvents being used for final recrystallisation, then it would absolutely be worth the hassle of trial-and-error'ing out the specific conditions optimal for each material. You're right Yeti, that would be huge!

  • Like 2

Share this post


Link to post
Share on other sites

Thanks for your thoughts Anodyne. I know the Phutthawong paper is a different idea - but felt it was worth including anyway - any shortcut to a cleaner extract, especially if it involved less use of solvents...

As for the paywalled paper - that one's going to take a bit of time to track down - my access to that journal does not go that far back. But from the preview - first couple of pages - it seems they had a similar set up to the enigmatic Mr Hogstad (but smaller). I haven't quite figured it out - but I have an idea forming...

I don't have time to research this today - lots to do. Will update when I've found some more info.

Share this post


Link to post
Share on other sites

Thanks for your thoughts Anodyne. I know the Phutthawong paper is a different idea - but felt it was worth including anyway - any shortcut to a cleaner extract, especially if it involved less use of solvents...

Yeah absolutely! Both ideas are interesting, I'm thinking it might even be possible to incorporate both: crash out the crud with method #1, then drop a fresh electrode inside a membrane-bag into the cleaned-up solution to attract the remaining dissolved alkaloids, adjusting pH etc as necessary. So maybe you could do the whole thing as a one-pot extraction?

Interested to see this thread develop!

  • Like 1

Share this post


Link to post
Share on other sites

I am going to have to lock myself away from this topic until I can get all my work done - doesn't help that it's way more interesting than what I actually have to do today.

I will throw a couple more links in though.

More Phutthawong on electrocoagulation (including for solasonine) http://www.mdpi.net/molecules/papers/11050309.pdf

A 1910 patent by a couple of German apothecaries on taking other stuff out of solution and leaving tannin behind (to use in tanning leather) http://www.google.com/patents/US975835

Share this post


Link to post
Share on other sites

Re. Electrocoagulation - now we are getting somewhere - Dechlorophyllation by Electrocoagulation - see attached.

11020156.pdf

Share this post


Link to post
Share on other sites

So all thats going on with this is forming and then using metal salts to form metal complexes from tannins etc.?

Share this post


Link to post
Share on other sites

I think it's a bit more complicated than that. Electrocoagulation is used a waste-water treatment method, and in that context the aim sees to be to crash everything out of solution. What Phutthawong et al seem to be able to achieve is a more selective outcome.

I'm still more interested in Hogstad - but Anodyne's 1-pot idea is interesting.

Share this post


Link to post
Share on other sites

I've just read the paper attached to the OP and it seems promising. In that one they are removing the impurities and leaving the alkaloid minus all the crud.

I think for some extracts, it could be very useful and avoid the use of a lot of solvent. It appears their EC setup could be easily reproduced with a couple of items from Bunnings for electrodes and a DC power supply. They used low currents (between 0.2-2.6 A, 19-31 V) so this would be pretty safe to do at home.

As far as getting pure alkaloids to precipitate out of a crude bulk, I doubt it. You're gonna get a lot of other compounds that are more greatly affected by the current than the alkaloids. As a pre-extraction step, it could be very promising. I am all for cutting down the amount of solvent needed.

  • Like 3

Share this post


Link to post
Share on other sites

As far as getting pure alkaloids to precipitate out of a crude bulk, I doubt it. You're gonna get a lot of other compounds that are more greatly affected by the current than the alkaloids. As a pre-extraction step, it could be very promising. I am all for cutting down the amount of solvent needed.

There are some other papers around which use slightly different processes, but at least in the one described by Hogstad in his patent above, the alkaloids don't actually precipitate out - instead they are just attracted to the electrode by the low current, and prevented from dispersing again by some kind of membrane (eg. a cellophane bag or clay pot). The alkaloid-rich solution is then siphoned off from this cell, and the process continued as required. He describes quite a few examples of crude plant extracts which all yielded alkaloids via this method (I don't know what kind of yields you would get, but I'd bet they could be maximised by tweaking the process, eg by repeating it several times using the siphoned-off solution). He also points out that in situations where an undesired component (or more than one) moves to the electrode faster than the desired one(s), a series of membranes can be arranged to separate them - a kind of crude chromatography I guess. The process only gives you a concentrated solution of crude alkaloids, you would still need to extract those (eg. by basifying into nonpolar solvent). But as you're working with a much smaller volume, the amount of solvent needed is much less.

So far in this thread we've discussed two different processes - the "electrodialysis" one I just described, and the "electrocoagulation" one you mention, MerryPrankster. And while I don't see any reason that you couldn't apply both techniques to the same extraction, they are separate techniques.

I had assumed that this "electro-dialysis" would use less current than the "electrocoagulation" (i.e. crashing out the crud) technique, but the currents Hogstad mentions in his patent are in the 0.8-5A range, which are actually higher than those MP gave. He also said he was using 220V direct current, but I don't know enough to know what difference that would make - I guess it would run faster, but be more dangerous to set up? He claims:

My present invention has many advantages over the methods commonly in use for the isolation, separation and purification of vegetable drugs, medicinals, organic acids, and the like. It makes unnecessary the use of the large volumes of solvents now commonly used. It greatly shortens the time needed for the production of finished products from the crude or original starting material. It permits the production of an extremely pure product, or of a comparatively pure product, as occasion may require.

Sounds pretty good, no? And while he may just be blowing wind, there's enough similar papers around supporting the idea that I'm inclined to put it to the test. I don't expect it'll be a simple process, I believe it's going to be fiddly as hell. But the potential pay-off is so great that I think a certain amount of tedious fiddly work (to get the right pH, electrode metals, membrane type & arrangement, and so on) would be worth it in the end.

Edited by Anodyne
  • Like 2

Share this post


Link to post
Share on other sites

I just had a quick skim through that patent and it seems like it would be easy for someone with a bit of technical know-how to replicate.

The author of the patent seems to be very caught up with the idea of filtration through the use of membranes etc, I can see an improvement that could be employed to refine that step and bypass much of the clogging problems and matching of pore sizes of screens and meshes etc.

If the box was re-designed as a labyrinth exclusion type of apparatus, the bulk of the sediment would be trapped and not make it to the opposite pole - bypassing much of the need for filters and meshes etc. Some would make it through but only minimal filtration would be needed.

By the time the alkaloids get to the anode the bulk of the sediment would be gone. Depending on the alkaloid of interest the polarity may have to be reversed, but the collection chamber should be smaller than the chamber where the plant matter is added.

post-7757-0-64210200-1448356588_thumb.jp

Edit: I wouldn't recommend anyone try something like this at 220 v (even if it is DC) without a good knowledge of electricity, and the unit would have to be built with the appropriate fail safe mechanisms. It doesn't take a fibrillation event to kill or seriously injure someone with electricity so even DC can be dangerous.

Edited by Sally
  • Like 3

Share this post


Link to post
Share on other sites

Good points Sally, I think I remember reading that some of the applications of electrodialysis, like those used for water purification, use a setup something like this.

Hogstad also points out that you can just make a coarse acidic extract (eg. boil in water + vinegar) of the plant material & then use the filtered solution as the starting point for the electrodialysis, rather than chucking the plant bits into the vessel.

Alternatively (or as well), you could try the electrocoagulation thing to crash out some of that unwanted crud, before attempting the whole business with the filtering membranes.

For water filtration, they also pre-treat the water in various ways, adjusting the pH & adding agents to help stop the formation of crap that might clog up the filters, which is another issue. Though I guess their filters are probably a tad more delicate & expensive than a canvas bag! It's worth noting though - not all of the filter-clogging crud necessarily comes from the original solution, some of it might be formed by reactions occurring in the vessel. At the moment though, I doubt that's going to be quite the issue for us that it is in water-purification, so I'm putting it in the "cross that bridge" basket for now.

  • Like 2

Share this post


Link to post
Share on other sites

Yeah they use similar setups in many different kinds of filtration procedures. The idea is that some contaminants will float and some will sink, so if the unit is run with a fluid level just above the lower vanes/elements (not quite full) you will trap all but the most soluble contaminants.

And the eletrocoagulation could be easily added as a phase in the system.

Edited by Sally
  • Like 1

Share this post


Link to post
Share on other sites

I think that for a home setup, the Hogstad patent is a bit prohibitive due to the high voltages involved. Sally is right, I wouldn't just go and grab a DC transformer and start playing with this. 200v is nothing to sneer at.

Perhaps if we boil the crude plant matter, filter as usual and boil down until it's pretty thick, then electrocoagulate (19-30V and 0.2-2.6A is much more friendly!) and remove the crap, boil down, electrocoagulate, rinse and repeat until you've gotten rid of majority of the crud?

  • Like 1

Share this post


Link to post
Share on other sites

As Sally and Anodyne suggests, design improvements can be made. Regarding the voltage, I got the feeling the Hogstad set up was relatively large-scale. Is size ever mentioned? I can't imagine that a small chamber of a litre or so would require 220 volts.

Share this post


Link to post
Share on other sites

He does give volumes in the initial description, but I'm having trouble converting (& reading) them. I think you're right about it being large commercial set-ups. I'll take another look.

Edit: friggin OCR, okay I looked at the original scans & if my maths is right the cell he's describing is about 7 litres, so not that big really. He says: "A potential of 220 volts is suitable for some of the operations hereinafter described in detail.." ...but also notes that this might vary depending on the conductivity of the starting solution. I think some of the later researchers like that Thai group were salting their solution, which maybe helps reduce the voltage requirement?

Edited by Anodyne

Share this post


Link to post
Share on other sites

Yeah salting would definitely improve the conductivity of the soultion. Aside from the lack of readily available low voltage transformers capable of delivering a high current in some labs, I cant see the need for such a high voltage potential. I could be wrong but the device seems to operate on the priciple of elctron flow not voltage.

I'm looking at my electric welder in a new light right now. It delivers a regulated 24.6 volt DC output and is capable of delivering high currents at a very high duty cycle. It would be much safer than 220v and quite easy to adapt electrodes for this type arrangement.

It would still have inherent dangers and require someone with a bit of electrical knowledge to use it safely, but it has the transformer that can deliver goods.

Edited by Sally
  • Like 1

Share this post


Link to post
Share on other sites

I'm starting to think a welder might not be the best starting point for this.

If there is a voltage drop across the electrodes (which would be very likely) when it's up and running, it could need to have the current cranked up to create an effective flow of electrons. So it could result in a few possible scenarios.

It could overheat the electrodes

or it could trip or possibly even fry an IBGT welder.

A small prototype might be a good idea. Maybe driven by a battery charger. Fill it with a salted acidic solution at an approximate working temp (say 60-70 deg c) and fit the electrodes. Then measure the resistance across the electrodes.

Testing & documenting the EC of the solution would help to establish some standard to base the other tests upon. Really most of the calculations could adapted from that alone but a bit of trial and error with resistance measurements would get the same point fairly quickly.

Without knowing the resistance of the unit before you start it up you won't be able to match a power supply to it.

After that the unit would have to be run with a voltmeter in series with one of the electrodes to check for voltage drop, then you could obtain enough data to match electrodes and a power supply that can run at 100% duty cycle safely.

& also the unit would be very likely to create gasses in operation, so it will need to be vented and run in a well ventilated area.

Edited by Sally
  • Like 1

Share this post


Link to post
Share on other sites

I was just reading through Anodynes' earlier post suggesting that it' more like electrocoagulation than electrolysis and to me it seems like that's more accurate.

I found a few other papers on the topic today and it seems like the electrocoagulation methods are using reactive metal electrodes to introduce metal ions into the solution to selectively coagulate specific alkaloids. Aluminium seems to be one of the more common choices.

Most of the newer methods seem to be using low voltages and relatively low current when reactive metals are used. It seems like when the current density of the solution gets too high alkaloids sometimes flow the opposite direct to what's intended and they can accumulate in both the catholyte and the anodyte solutions as a reversal of charge can occur.

http://www.sciencemadness.org/talk/files.php?pid=75795&aid=1753

& I think the picture I posted above wouldn't be a very effective design as the current wouldn't be flowing through the plant material. If one electrode was on or very close to the bottom it may work, but maybe a 3 chamber device (plant matter in the middle) with mesh filters would be easier.

Edited by Sally
  • Like 1

Share this post


Link to post
Share on other sites

Super interesting idea, thanks for sharing Yeti (PS Hope all is well!!)

There is absolutely no need for high voltage. Only reason you might want to go high voltage is so that the current can increase because with regular off the shelf (so to speak) electrolysis current is the driving force. I believe, but am not 100% certain that a higher current would result in a quicker reaction. Only thing I am a bit skeptical or worried about with testing is whether the alkaloids would have any of the electrode material in them, maybe someone more chemistry minded can chime in regarding this.

To do a proof of concept of this idea why not as Anodyne pointed out do an acid wash say vinegar so that you know you'll have an acetate salt and not have to worry about filtration until you can see how well this idea works before complicating it by filter a whole heap of crap out.

Anyone actually going to try this out? I would love to lend a hand with my electrical knowledge to someone actually trying this out. If you don't mind waiting such a thing could theoretically be done with lemon batteries like a modified version of this, no need for complex electronics and you know it would be 100% safe no risk of anything blowing up just mightn't be as efficient as a battery circuit:

http://www.instructables.com/id/simple-electrolytic-cell-made-with-citrus-fruits/

If you want a more high tech version do an acid wash of the plant material, filter that and then use a multimeter to measure it's resistance. Then send me a PM and I will happily help set you up in the name of science.

Shamanistic

  • Like 3

Share this post


Link to post
Share on other sites

Sounds very similar to electrolytic rust removal - and if you use the search engine to find "electrolytic rust removal power supply" you'll find some fabulous circuits for voltage/current control.

I have a 15A 10-15v pwm DC motor speed controller that operates at 30khz - cost $10 off ebay and works a treat as a 12v variable amperage power supply. Here's one thats 6-90v 15A that would do the job: http://www.ebay.com.au/itm/6V-90V-15A-Pulse-Width-PWM-DC-Motor-Speed-Controller-Switch-/261888617437?hash=item3cf9c72bdd:g:k8MAAOSwv0tVUdWO

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×