Isomerization of D9-THC to D8-THC

Hello everyone. First off, I’d like to thank the community for sharing all the knowledge and making this industry a better place.

Anyhow, I’m quite new to the industry and have been running into problems with my distillate. The final product that comes out looks amazing, golden in colour and clear throughout. Viscosity could not be better, its so thick that if the 5ml vial its stored in is turned upside down, it would take hours to go down. However, when i got it tested, although the total THC (D9+D8) is over 96% and total cannabinoids percentage is 99.4%, the product is inferior because there is a near 20% D8-THC in it and i have no idea what is causing this isomerization from D9-THC to D8-THC.

The process i use is cold ethanol extraction. General flow is usually soak biomass, carbon scrub, filter, filter again, rotovap, then distill. Biomass is low quality trim and both biomass and ethanol taken to -80C before soaking.

I use to winterize at -80C but then realized that the waxes and lipids I’m pulling off are very little so i just skipped it altogether.

I use a short path for dilstillation. Boiling flask temperature hardly ever reaches 200C and main body is mostly good but sometimes appear darker than I would like it to be. Vacuum pressure is usually always under 150microns.

Couple of reasons i think why my THC is isomerizing is due to heat involved, possible leak in vacuum (not enough to affect ultimate vacuum levels but enough to introduce oxygen in my system), or possibly acids in my crude that is catalyzing the isomerization.

Any insight into this would greatly be appreciated, thanks so much.

Why do you consider D8 to be inferior?

Have you measured the ph of your oil?


We just sent in our first disty test and had similar probs i think. Someone else on the crew made it so not sure on the process but here’s the results.

I feel like these are not the results we are lookin for.


That honestly looks like a really interesting spectrum of cannabinoids. You might want to document that process for future consideration.

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In a good way? haha

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I think so, I’d definitely like to try a mix along those lines and see how it does with several chronic conditions in my family.


You’re absolutely right, “inferior” was probably an incorrect word to use since there are a few companies that are trying to isolate D8-THC.

Undesired result would be more correct. Our people wants potency and purity, anything that is not D9-THC is usually passed off as unwanted.


These are our results. Very similar indeed but it seems like we have a little less degradation to CBN and about half the amount of isomerization as you guys did.

Also, if i do a second pass, would this perhaps remove some of the D8-THC? I would think it would create more than previously.

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Also, I have not tested the pH of my oil. I ordered in a pH meter but a little concerned as to how accurate it may be. Will update once i have pH meter. Thanks.

I wanted to say that I’ve tried something like your coa shows, and i’ve tried 100%d8, As a long time cannabis smoker(45yrs) and distillate vaporizing, the different combinations, or i guess different ratios of d9/d8 is what the future beholds. I guarantee it. I only know of one major player that’s already started to explore it. Mark my word.

Are you putting your dry ice directly into your ethanol to chill it?

Do you filter out your charcoal through a sub micron filter or use DE/celite as a filter aid?

Both of these things would cause some acidity to make it’s way into your boiling flask and likely account for these issues.


Hi there mate :grinning: sorry but a second pass likely will be insufficient for separation because the boiling points are to close. I can tell you weak acids like carboxylic acids can cause isomerizations, as well as strong acids like HCl. CO2 like dry ice forms carbonic acid which can cause your isomers. I think your issue could also be heating related and residence time. Whats your run time to remove the main fraction? From your CBN i also suspect you’ve got some air. Can you get below 150 micron? I like below 10 :grin:

I’ve done 12 hour runs with the flask at 220c and got barely a hint of d8. I don’t think air, residence time, or heat will cause much isomerisation into d8.

I’m 70% sure it’s a pH issue

Thanks everyone for the helpful advice.

I’ve solved the problem and no longer getting D8-THC. It turns out that we had a vacuum leak and oxygen was getting into the system during distillation. After fixing these problems we managed to get 96% D9-THC no D8-THC or CBN and above 99% cannabinoids. Its always the smallest thing that can bring down entire methods.

The most i can get from my system is around 100 microns, i think that okay considering i’m working with mostly glass joints. Pulling below 10 is quite impressive, i can’t imagine my equipment every being to go that low.

Also, are you using mostly glass setup?