Decarboxylation Efficiency

#1

Hi all,

I’m wondering if any of you with in-house analytics have done studies to optimize decarboxylation efficiencies. What are you typically seeing for these values?

Theoretically at 100% efficiency, 1 kg of dry, non-decarb’d extract that is 100% THCA by mass would yield you 880g of 100% THC after accounting for mass lost during decarb.

Anybody have an efficiency value that they’re getting that they would not mind sharing? Ours are 70-75% which seems low and I’d love to compare.

Thank you all.

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#2

Hmmm ok what methohod of decarcoxilating are you using
Crude is never 100 % thca
And a lot of volitales and left ssolvent make up for the 1 kg of crude wich if well winterized is less than one liter
Second who calculates your numbers by wich machine and wich comparisons

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#3

Hot plate heating. My example was only theoretical of course. I know there are volatiles/solvent leftover.
We use HPLC for analytical testing. I am saying we have a potency after rotovap/before decarb, and also have potency post-decarb. By mole ratio, what is the max efficiency? Considering there are side reactions when heating to 140C.

#4

The theoretical conversion of THCA into d9THC is .877, but the real conversion rate is .68 because the reaction does not occur perfectly. So 100 grams of THCA converts to 68 grams of d9THC in the real world.
Hugh Goldsmith
SRI Instruments
We make the equipment to measure the THCA and d9THC

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Its all about the Delta 9
#5

Thank you Hugh for your actual results!

#6

What does the rest of the thca turn into? can you seperate it from the thc?

#7

@Krative @wc15 @Dabatronicus,

What do you guys think about this statement?

Does THCA really turn into other things besides delta 9 when decarboxylation occurs?

#8

Yes. In it’s established that there’s always going to be side reactions occurring - reactions with oxygen, solvent, two THC(A) molecules coming together, etc. However, @Sunslabs I don’t believe we know the identity of the other ‘decarboxylation products’. I doubt all of them would be desirable.

If you have access to pure THCA and an analytics company that you trust, try taking pure THCA and decarboxylating it. Unless you find the absolute magical conditions, I am sure you won’t get the purity of the resulting THC to match or exceed the THCA purity.

Although, there are definitely ways to get more than the .68 d9THC conversion that @srihugh1 is reporting. I’ve around 95% (so 0.95 * 0.877 in terms of mass) (keeping in mind that the analytical results will have some error in them).

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#9

I used to decarboxylate quinolines back in 2016. I would never see high yields since the temperature to decarb was around 180 *C. This is about where you start seeing radicals come in and do work.

A typical radical reaction is:
Initiation
Propagation
Termination

Now the problem with radicals is that you cannot really control what they do. The initiation step is where a radical is formed. Propagation step involves a radical making a new radical. The termination step is where two radicals form a new bond and the reaction is done.

Now look at propagation. Literally anything can happen here. You typically make a carbon soup and try to purify what you can out of it. It would be advantageous to start looking at transition metals to help with the decarboxylation step.

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#10

I was recently getting a consistent 83-85% from
ethanol-extracted THC crude though I wasn’t measuring how much was already decarboxylated or how much residual solvent. Rotos were only running at 65°C so there may have been a small amount of both. The lowest empirical data I’ve heard of on THC crude was around 80-81% I believe (which I believe lines up with my lowest numbers).

Someone try it with pure THCa crystals, under deep vacuum, please.

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#11

You can prove it to yourself.
If you have an HPLC:

  1. Inject the THCA standard to verify it is really 100% THCA and has not already decarboxylated in storage. If you don’t see a d9THC peak then its OK.
  2. Calibrate on a d9THC standard ( the Restek synthetic 100% decarbed standard ).
  3. Externally decarb the THCA by evaporating 100ul of the methanol solvent ( the THCA comes in methanol ) and then heating the residue at 150C for 20 minutes. You can try decarbing at other temperatures for comparison. If you heat too hot for too long you will make CBN.
  4. Re-dissolve the decarbed residue in an equal volume ( 100ul ) of clean methanol and then inject into the HPLC. You should see a d9THC peak only, no THCA. Since you are calibrated for d9THC you will get an answer. I predict that answer will be the .68 number.

If you have a GC:

  1. Derivitize the THCA standard and inject to verify that it has not decarbed. If you don’t see a d9THC peak then its OK.
  2. Externally decarb the THCA standard as with the HPLC above.
  3. Calibrate on d9THC
  4. Inject the externally decarbed THCA and get the result. I predict it will be .68.

See this explanation from Steep Hill Labs in CA. Its not very clearly stated, but if you read it they say that they get a 75% conversion efficiency after the 12.3% mass loss from the decarbing. So they have the formula where they first multiply the THCA result by .877 and then multiply that by the 75% efficiency number to get .66.


Its worth noting that in most states, the law requires the HPLC lab to multiply the THCA number by .877 and then add that to the d9THC result to get the “total smokable potency”. They are not allowed to use the real number. Why you might ask. It may have to do with generating the highest possible result.

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#12

Thanks for the in depth analysis!

I believe that decarboxylation procedure you’re describing can be optimized, though. 150 C is far hotter than necessary, and as @wc15 said, at higher temperatures radicals are going to mess up your yields. I believe it can be optimized to get a 95% conversion, or 83% mass balance.

@wc15 did you notice anything that you could change to improve your yields? Solvent degassing and running the experiment under vacuum, for example? I imagine if you were able to lower the temperature that would help. I have read on here that you can add MgO (food grade) and CaO powders to lower your decarb temperatures as low at 90C. Anyone have experience with that?

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#13

If you can achieve a better yield then that’s great, but in terms of the test results you get from a 3rd party lab you can see how they are biased depending on the multiplication factor the lab uses. If you compare the test results from a GC and HPLC, the GC number gives you the real answer because the GC decarbs the sample according to the .68 while the HPLC number is fictional.

#14

I would decarb in deuterated water back then. It would apply here.

I can design an experiment for this when I get back into a lab.

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#15

PM me for a derivitization SOP.

#16

Extract 100mg of cannabis into 40ml vial of methanol, ethanol or acetone.
Measure 30ul of your extract containing a mix of THCA and d9THC into a small vial.
We use 300ul vial inserts which are about 5 cents each on Amazon.
Use an aquarium pump or some small air compressor to evaporate the solvent to dryness.
If its an Acetone extract , this will only take about a minute.
The evaporation step is necessary because any methanol or alcohol will prevent the derivitization from happening.
Add 30 ul of MSTFA to the vial to re-dissolve the THCA/d9THC scum in the bottom of the vial.
Rotate the vial as you pump the injection syringe to wash the scum off the inside of the vial walls.
Inject 1 ul of the MSTFA/dissolved scum into the GC. The deriv reaction occurs instantly.
You should see two peaks, the derivitized d9THC and the derivitized THCA.
To calibrate the cheap way follow the above procedure with the Restek standard.
This standard is 100% decarbed synthetic d9THC. Use the same calibration for the deriv THCA and the deriv d9THC.
If you have more money to invest, buy the THCA standard and calibrate on it after verifying it has not already decarbed in storage. When you deriv the THCA standard you should not see any peak at the retention time for derivd9THC. If you do, then the THCA standard has already partially decarbed.
Its not a deal breaker, you just have to adjust the numbers to reflect how decarbed it is.
See this video https://www.youtube.com/watch?v=qqcsa8Pzf94
Hugh Goldsmith
SRI

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#17

This thing claims 100% potential conversions rate. It decarbs around 90C for 90 mins.

I did some quick tests and got somewhere around 95% decarbing bud. But who knows if my results were really accurate?

#18

But isn’t there more error with a sample that is run on GC-FID since its decarbing DURING the analysis?

#19

The sample extract decarbs in about 3 seconds at the instant its injected into the GC and before any of the molecules get into the column or detector. You could argue that the instant decarbing is somehow different than a slower decarbing, but you can prove to yourself that its the same.

  1. Take a fresh flower sample that is mostly THCA and make the normal extract of 100mg in 40ml of solvent ( acetone or alcohol ).
  2. Inject into GC and get the “total smokeable potency” ( THCA + d9THC ) ( TSP ) result.
  3. Take 50ul of the same extract and evaporate the solvent. Then decarb the evaporated residue any way you like. Re-constitute the decarbed sample with 50ul of clean solvent so you are back to the original strength.
  4. Inject that into the GC and compare the results.
    You will see that the results are the same between letting the GC do the decarbing and doing it externally.
    The real error occurs with the HPLC analysis where there is no decarbing. There is major uncertainty about the actual efficiency that THCA converts to d9THC, The HPLC COA assumes a theorectical conversion rate of .877 from THCA to d9THC when the real conversion rate is about .68. So the HPLC results overstate the “total smokeable potency” by a lot.
    The GC-FID measures the real TSP
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#20

i would love to see your source, and/or data on this. my work every single day disagrees.

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