Assessing THC purity through decarboxylation

Hello Future4200 community!

First post here!

I recently conducted an experiment on decarboxylating THCA crystals to convert them into THC. The purpose of this experiment was not only to achieve complete decarboxylation but also to understand the purity of the resulting THC compound. I’d love to share my findings with you all and hear your thoughts.

(Thank you ChatGPT for putting my thoughts in order)



  • 10 grams of THCA crystals (centrifuge Tek)
  • Oven capable of maintaining 248°F (120°C)
  • Digital scale accurate to 0.01g


  1. Weighed 10 grams of THCA crystals and placed them in an oven-safe dish.
  2. Set the oven temperature to 248°F (120°C) and decarboxylated for 90 minutes.
  3. Weighed the resulting material after decarboxylation.


After the decarboxylation, the final weight of the THC was found to be 8.88 grams, a discrepancy of 0.11 grams from the anticipated 8.77 grams (calculated with a 12.3% mass loss due to decarboxylation).

Purity Calculation:

To assess the purity of the resulting THC, I used the following formula:

\text{Purity of THC} = \left( \frac{\text{Anticipated weight of pure THC}}{\text{Actual total weight of product}} \right) \times 100

Plugging in the numbers:
\text{Purity of THC} = \left( \frac{8.77}{8.88} \right) \times 100 = 98.75%


According to this calculation, the THC is 98.75% pure, with the 0.11 grams potentially accounting for impurities or other variables.

Question for the Community:
Do you think this is a reliable way to calculate THC purity post-decarboxylation? Have any of you used similar or different methods? Your insights would be incredibly valuable!

Much appreciated!



@cyclopath @Photon_noir

This is not the standard method for determining an ASSAY of THC in a compound. That’s done with different analytical instruments.

I’m not sure what you are looking at the “purity” for.

Do you want to know when decarb is finished? Are you trying to establish without doing any analytical testing of the compound itself a potential potency level?

I’m not sure that this is appropriate as there are multiple compounds that can be found and recrystallized with THC that also decarb (CBG and CBD for instance…) so you wouldn’t know if those were present.

Also - during this normal setpoint you have listed terpenes and other things that might be left over from centrifuge TEK would also be present and would also off-gas during this process.

This process could be good for determining your YIELD and thereby knowing if things are fully decarbed or not, potentially.

But I don’t think that’s the information you were hoping to get from this experiment.


This is not an accurate way to assess THC purity. Firstly, how do you know that your centrifuge tek THCA is 100% THCA? Also, you are not accounting for the biproducts that are produced while heating THC/THCA (mainly CBN).

If you knew the starting potency of the THCA you were decarbing, your procedure could give you an idea of decarboxylation completeness. But don’t rely on this method for determining potency.


Name some potential impurities that will volatilize.

Name some that wont.

See the problem?


Not sure if you @SevenTen808 or anyone in the future reading this knows, but there are testing centers in most states nowadays.

For someone that really wants to know their potency, it is fairly trivial to set up an account with a certified testing lab and pay less than $100 (some as low as $20) to get a simple HPLC potency assay for R&D purposes.

You can test as an individual in a lot of legal states, but I’m not 100% sure, except for my own state AZ which you definitely can. Some labs will accept samples from out of state even, in case you don’t have a local testing center.

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I’m assuming any leftover terpenes would volatize/degrade minor cannabinoids, waxes etc won’t.

Yes this answers my question.

It seems that proper testing is essential. Unfortunately my state only allows medical and there are no testing facilities on my island. Getting a sample over to Honolulu for testing would require breaking federal laws… I don’t know how the two medical dispensaries we have here pull it off.



Unfortunately Hawaii; and my county in particular don’t have readily available testing facilities…. I’d happily spend the money!

I don’t know how I’d legally transport a sample to another state for testing. Everything needs to get on a boat or plane to get anywhere and that’s federal.

I don’t know how often you are wanting to do these tests. But - you could consider checking out local colleges with chemistry programs, who often have HPLCs that could do this work.

I imagine the medical facilities have some kind of testing for their in-house work - perhaps you could chat them up.

Also - there’s quite a few of us on here who have purchased old school GCs and HPLCs on ebay and what not. I bought my most recent GC for $350 and it can now do residual solvents, potency, and some pesticides. :slight_smile:

Check out this thread - I bought a thing!: Adventures with a 20-year-old GCMS

You probably even have some in Hawaii - so you could save on shipping. I don’t mind helping you get whatever you find figured out. Or helping talk to the local chemistry departments - who are often way cooler about these things than you might expect.


I’ve shipped testing samples across the country with no problems through USPS, FedEx, and UPS. Still a good idea to vac seal or otherwise contain any smell before you throw it into a small USPS flatrate box along with any COC forms the lab needs and cover the outside with clear packing tape so it can’t pop open during transit.

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