Improved chlorophyll removal method

Figured this may be helpful to some ppl here, a simple, instantaneous way to remove chlorphyll from crude extract that is far preferable to winterization, as it targets only the chlorphyll and prevents the loss of terps/cannabinoids when winterizing an extract.

(edit: this is poorly worded, it isn’t an either/or thing. This tek is preferable to winterization at removing chlorophyll, but some waxes/fats will remain. Combining it with some gentle winterization afterwards - that is, less time and/or warmer temps - is probably the best technique)

To start, it’s helpful to understand a bit about the chemistry and why winterization also removes some of the desirible compounds along with the waxes/fats/chlorophyll. Winterizing works by lower the solubilty of the solute in the given solvent. The waxes/fats that were soluble in your solvent at 20 C are much less so at -20, and so precipitates out during winterization. The problem with lower the solubility by temperature is that you cannot targe individual compounds…lower the temperature of a solvent lowers the solubility for ALL compounds in solution. Not equally, of course, and the compunds with the lower solubilities will precipitate out MORE than the ones with higher ones. Since chlorophyll/waxes generally have lower solubilities than other compunds present in crude, they’ll prcipitate out the most. But a loss of the desirible compunds is inevitable in winterization. This chart is a good way to visualize it. Basically, anything below the red line is going to make up the bulk of the precipitate.

Because the cannabinoids generally have higher solubility parameters than many of the terps, as well as the waxes/fats, their loss during winterization could be minimized by ensuring ideal solvent/solute ratios (but the ideal solvent amounts can be hard to figure out without doing a lot of complex chemistry math). That’s the good news. The bad news is, a lot of desirible terps have solubility parameters that are much closer to chlorphyll/waxes/fats and their losses can be a lot higher.

The chart doesn’t show methanol, but it’s solubility parameteris 36.2, compared to ethanols 26. This explains why methanol is a better extraction solvent, and a better winterization solvent as well…b/c it “holds” onto the cannabinoids better, so you’ll extract more than you would using an equal amount of ethanol. But it’s also got a “looser grip” on the fats/chlorophyll/waxes since it’s further away on the chart than those compunds, and will precipitate them out easier than an ethanol extraction. yes, it will also lose more of the terps in the 15-20 range than an ethanol extraction would, but if I have to decide between losing terps and losing cannbinoids, I choose the terps.

(incidentally, the entire report that that graph comes from is definitely worth reading in it’s entirety, you can find it here

In other words, winterization is a blunt instrument…it can remove chlorphyll and fats/waxes, but it will also remove desirible compunds as well. The way that I remove chlrophyll from my own extracts is a much more precise technique which targets only the chlorophyll. It’s also easy to do, and will remove the chlorophyll instantly. All you need are acetic acid (cleaning vinegar that you can get at any grocery/hardware store is fine) and copper oxide (can be had on Amazon for $15/lb or so).

First you need to create copper acetate, a blue water soluble salt. This can be done easily by boiling cleaning vinegar and stirring in copper oxide. The amounts aren’t really that important, I just eyeball it. I’ll just bring a few hundred ml of cleaning vinegar (10% acetic acid) to a boil, and add the copper oxide, put a magnetic stir bar in and leave it for an hour. what you’ll see is the vinegar has become a blue liquid. There may or may not be a black powder at the bottom. That’s unreacted copper oxide. If CO remains, all that means is you’ve reacted all the acetic acid in the vinegar into copper acetate, and no more remains to react the rest of the CO. You can either filter the solution to remove the unreacted copper oxide, or just add more vinegar until all the black powder has reacted. Usually, I’ll filter the solution with a bit of CO left in it so that I know I’ve reacted all the acid and I’m not carrying over any with my copper acetate, then just toss the unreacted oxide. You can keep it I guess, but it’s so cheap it just seems like a hassle to me. Then just boil away the blue solution and collect the blue salt that remains. This is copper acetate.

Then all you do to remove your chlorophyll is create a saturated solution of copper acetate in water and start adding it to your crude extract (I use methanol, but ethanol will work too). Measuring isn’t that important, you’re going ot be washing the extract with an organic solvent afterwards, which won’t pick up the copper acetate). You’ll instantly notice a lot of precipitation happening. This the chlorophyll. What’s happening is the copper acetate replaces the magnesium core of the chlorophyll with copper. Copper-based chlorophyll is much less soluble than the regular magnesium-based chlorophyll, and so it drops out of solution. Unlike winterization which drops the solubilities of ALL the compunds, copper removal only drops the solubility of the chlorophyll, which makes it a much more targeted technique than winterization. Let it sit for an hour or two, and then filter the extract. Once the extract is filtered, drop in some more copper acetate. If you see the same, goopy, amorphous precipitation, that means there’s more chlorophyll in the extract and repeat step 1. If instead you see a dark-bluish materiel forming on the bottom, that is simply the copper acetate coming out of the methanol solution. since copper acetate isn’t as soluble in alcohol as it is in water, when you drop a saturated solution of CA into an extract that doesn’t contain any more chlorophyll, the copper acetate has no where to go and just drops out of solution. This provides a handy way to know when you’re done. The copper chlorophyll precipitation is easily distingushed from the copper acetate precipitation, so you can be quite precise about exactly how much copper acetate is needed. When all is done, you should have a solution that is bluish in color, but much clearer than when you started.

At this stage, you can go two routes. You can winterize now to remove the remaining fats/waxes (remember, the copper acetate only targets chlorophyll, not the other undesiribles). If you do this, do a much more gentle winterization. don’t go below 0 C, and don’t leave it too long. Your extract is somewhat vulnerable now to a harsh winterization b/c now that the chlorophyll is gone, it’s easier to start cutting into your terps/cannabinoids. I just throw mine in the fridge for an hour or so and remove the samll bit of precipitate that sits on the bottom. Any more than this is unnecessary. The reason the bluish extract solution is clear post-chlorophyll removal is that chlorophyll makes up the bulk of the undesirible compunds, which is why further winterization is (in my opinion) more likely to cause more harm than good.

Or if you don’t want to purify any further, you can simply do a wash with Hexane (or chloroform, or DCM, or any immisicible organic solvent) and recover all the good stuff. You’ll notice that when you start the wash, your organic layer will be clear and your exrraction layer a dark blue. After the wash, organic layer will be a clear amber color, while the aqeous layer will be a light blue. That’s why you don’t need to be overly precise with adding the copper acetate, because it’s completely insoluble in any of the organic solvents and so it’s staying in the water layer. Before you do the wash though, I strongly recommend evaporating your alcohol off, preferably in a rotovap. If I had 1 L of post-chlorophyll removal extract, I would add about 200 ml of water to it (20%) and then gently rotovap the methanol out. While this isn’t crucial, the presence of the methanol will make the aqeous layer more soluble to the cannabolic acids, and so some will remain in the aqueous layer. If you don’t have a rotovap, or don’t want to remove the alcohol, I would dilute the solution to a 1:1 alcohol/h20 ratio before the wash. This will greatly reduce the solubility of the cannabiolic acids in the aqeous layer, and push all or most of them into the organic layer.

(side note about washing, due to the way solubility works at the chemistry level, i.e. Kpa/Ksp values and the like, it’s preferable to use smaller volumes of solvent relative to the crude solvent. Three washes of an equal volume is how it was taught in school. So if I have 1 L of crude extract, I’lll wash it with 1 L of Hexane, but rather than do one wash with 1 L exract/1 L hexane, I’ll do three washes of 1 L extract/0.333 L hexane)

Also, an added benefit to this method is that when the copper leaves the solution in the form of copper chlorophyll, the acetate ion it was attached too reverts back to acetic acid. Acetic acid reduces the solubility of THCA and CBDA in the aqeous solution even more, which will push more of those acids into the organic layer.

Pictures:


Acetic acid/Copper acetate solution, with unreacted copper oxide on the bottom

Filtered and evaporated copper acetate salt

Extract before adding copper acetate

5 minutes after adding copper acetate

After 1 hour

The black substance at the bottom (it’s actually a dark blue) is precipitated copper acetate. You can see it’s easily distinguished from the copper chlorophyll precipitate. The appearance of the dark blue acetate precipitate is used as an endpoint which tells us that all the available chlorophyll has been reacted.

Filtrate

final product (although needs another run through the filter as a little bit of the filtrate slipped through)

Organic wash to recover cannabinoids from the copper acetate solution. I’m using DCM here (whcih is why it’s on the bottom layer). this is before shaking, you can see the organic layer is clear (slightly yellowish, probably just from picking up minute amounts of solute on it’s way down to the basement)

After shaking for 20-30 seconds. Note the color change in both layers, the aqueous layer has become a beautiful sky blue after losing all the plant matter to the organic layer, which looks like a much more typical cannabis extract.

2nd wash (before shaking)

After shaking. Note the organic layer is more clear, and a lighter amber. This is because the first wash mostly removed the terps/THC (and fats that reminaed in the extract), and the second wash is primarily the cannabinoidic acids. I expect the organic layer on the third wash will come out basically the same color as it goes in, as there should be very little left to collect from the original crude extract

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This is a very cool idea and detailed write up thank you for sharing!

I think many people only use winterization for removal of waxes so this would probably be perfect to add at that step.

Wondering if you’ve had any metals testing done of the final product. I can imagine that although copper acetate isn’t soluble in hexane the copper/chlorophyll complex probably is. If your precipitation/filtration step leaves behind any of that complex, isn’t the copper now stuck in the remaining chlorophyll, which remains after filtration/washing?

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Excellent write up and a very interesting read. I’ll be playing around with this :slight_smile: :call_me_hand:

Would a saturated brine solution have a similar effect?

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oh yeah, I see the confusion. I meant “final product” as in, the final product after filtering the chlorphyll, but that’s prewash. Just added pictures of the wash which shows what the REAL “final product” will look like.

I’m doing this as I’m typing it, and just taking pics along the way lol

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also, to answer your other point, yes, that’s correct. The copper/chlorophyll complex isn’t insoluble in the extraction solvent, just significantly less soluble than the regular magnesium based one. There will still be SOME of the copper chlorphyll in the solvent, and further winterization will probably remove it, as well as the fats/waxes that the copper acetate won’t touch. I would be much more careful though, as I mentioned above. With the bulk of the chloropyll gone, the regular winterization protocol will cut into the terps/cannabinoids more so (depending on, of course, the specific factors unique to each extraction, such as the exact solvents used, solvent volume, amount of plant matter present, temperature etc etc)

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it works in the same way, that is, by dissolving solute in the solvent, it makes the solvent less soluble to other solutes. A rough analogy would be to imagine a solvent like a storage locker. It’s got a finite amount of space, and for every item you place in it, that reduces the amount of space for other items. The point of the brine solution is to use an unimportant solute to “take up room” in the solvent, which leaves less room for the desirable compounds to hang out in. Adding some NaCl to the aqueous layer is a good idea. It will help with breaking emulsions too.

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This is a cool technique. Do you have any picture of what the evaporated oil itself looks like after this treatment?

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It doesn’t look like much, just the same brown goop (just less goopier? Lol). I just cold crash my crystals straight out of the organic layer. The thing I’m not sure is well understood is that terpenes themselves are excellent organic solvents, and it’s much easier to crystallize the acids out of a solvent like hexane or pentane than no solvent, as the solubility of the acids in the organic solvent is lower because of the dissolved terpenes. Without an organic solvent to dissolve the terps, the terps will act as a solvent. And without anything else to “take up space” in the terps the way that terps do in an organic solvent, the acids are much more soluble.

I’m going to pick up some dry ice later on today for the crash, I’ll post pics of that

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This is phenomenal, thank you @TheMadChemist!

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Great share. This is one of the reactions I was speaking about in the blue diamond thread. Still wind up at this reaction when I think about them damn things. Anthocyanins instead of copper. Amazing to see you dropping chlorophyll this way.

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I wonder if maybe there’s some way to use ion exchange to do this

I know in the wine industry they are able to lighten the color of wines with a similar technique

I totally think it’s possible

They use a similar technique to remove positively charged ions from water that cause scaling

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Definitely possible. This is why they called it “ion exchange” in the first place!

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The problem is finding something that will want to exchange with it, I don’t think 2 sodium ion will replace that magnesium ion, if they did though it would make chlorophyll water soluble

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Beautiful write up! It was super easy to follow along! Thanks for taking us along. :man_scientist:

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Yeah, good call. I actually think the most likely method the blue diamonds are made is simply by adding copper acetate to ethanol/methanol to create a blue solution, dropping in some diamonds, and then precipitating them out. the resulting diamonds would be blue in color.

Of course, there would be copper impurities, but I don’t think that would be harmful. I actually stumbled across the copper chlorophyll idea from a patent that creates copper chlorphyll and isolates it as a value product itself, which is then marketed as a health supplement. The difference here is that for our purposes, we’re viewing that chlorphyll as a waste product instead of a value one

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I mean, that’s literally what’s happening. You’re exchanging the magnesium ion with the cupric ion. Any of the complicated ion exhcnage processes using membranes and resins and such have the exact same end goal. It’s just that in this example, the chemistry is simple enough that none of that is needed.

As I type this though, I wonder about using other heavy metals to do the same thing. Since one of the main factors of solubility is molecular size, exchanging the magnesium ion with a bigger ion may result in even more chlorophyll reduction. The larger chlorophyll molecule should (in theory) should make an even less soluble chlorophyl complex than the copper one. This is why the copper chlorophyll complex has lower solubility than the magnesium one, because the Cu ion is over double the size as the Mg ion.

Looking at the periodic table, silver stand out as an interesting possiblity. It’s got a 2+ charge, same as copper & magnesium, and it’s
molar mass is 107 g/mol, compared to coppers 63 g/mol and magnesium’s 29. Silver acetate can be made with a colodiol silver solution and nitric acid. Could be an interesting experiment someday.

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Aren’t all sodium ions water soluble? If we could somehow exchange the magnesium with 2 NA+ ions I bet we could water wash the chlorophyll out using LLE

I have no experience with this so I’m shooting in the dark

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thats sound logic, and you’re correct in the sense that substituting a Na ion in place of an Mg ion WILL make the chlorophyll complex more water soluble. But “more” in this case is a relative figure. The cation at the center is only a small part of the solubility of the complex. The bigger factor is the long hydrocarbon tail ATTACHED to the cation. . By exchanging the Mg ion with a Na one, you might increase the water solubility from a really really small number to a slightly more than really really small number, but chlorophyll will always be effective water insoluble.

You CAN make it into chlorophyllin by saponifying it with NaOH, and chlorophyllin IS water soluble. Be aware though that adding NaOH converts all the cannabolic acids into the salt deriviative of the hydroxide used (NaOH will convert THCA into sodium cannabinate, for example, and KOH into potassium cannabinate). That said, that may not be a bad thing, just something to be aware of.

In fact, when I do my extracts, I like to basify the crude extract and do a chloroform wash, which gives me an aqeous layer with all the salts, chlorophyllin, and various other bits of plant-based hodgepodge, and an organic layer with the terps, and the THC. I’ll then neutralize the aqeous layer and extract back into an organic layer (DCM this time). Cold crash the acids, and than recombine with the terps as desired.

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Absolutely love this thread. More chemistry please. I cant get enough of this.

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well, if you like long, nerdy posts that go deep into the chem weeds, you’re in luck, just posted this monstrosity :laughing:

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