After a long time away from my chemistry background I recently joined a team primarily (legally) producing
THCa/THC oil for vaping.
During decarboxylation I would like to be able to monitor the process of the reaction and I believe this can be done semi-quantitatively with a simple TLC analysis. I have read a good deal of literature on the subject and found the array of carrier solvent combinations is extensive while the solvents at my disposal are not!
I’m hoping just to use a basic ethanol and or ethanol/acetic acid carrier. Is anyone out there doing this?
Will I be able to see results without UV (the oil is a dark amber)?
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It can be done relatively easily by using a gas chromatograph and some basic acetone from a hardware store. Here’s a video from SRI instruments. I don’t work for them but I do run the 310GC. It’s pretty simple. You’ll just need to order the standards from restek, follow the video Hugh set up and you can’t fail, it’s a real simple and accurate way to test raw material. I in fact have developed a method for testing gummy bear potencies that nobody has thought of. The labs imo are struggling with edibles which is why they are backed up.
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Did you mean to post a link to the video?
Yes. Sorry about that. New puppy in the house distracted me. Haha. Once you click on the link you’ll see all their videos.
https:/ /youtu.be/_JrTSCI4MMw
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It wouldn’t let me post the complete link so just take out the space in / /
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https://m.youtube.com/watch?v=_JrTSCI4MMw&feature=youtu.be[quote=“Surfer_Steve, post:4, topic:10722”]
https:/ /youtu.be/_JrTSCI4MMw
[/quote]
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If I had access to a GC that would be great but I’m really looking for info on a quick TLC test.
Thanks for your reply!
The color in your oil could be coming from a non-thc/thc-a compound. Do not use the movement of a colored spot for rf unless you know the compounds co-elute/or that the THC/THCA is truly colored.
Your guess for EtOH/Acetic acid is probably in the right ballpark. The THCA likely won’t move without acid in the carrier solvent.
Another common approach is to douse the plate in an acidic solvent (HCl/Meoh) and place it under high vac for a half hour before running. You will still need a small amount of acid in the carrier solvent, but the spots might run cleaner.
If you ever have a basic compound to run, using triethylamine to remove acidic sites from the solid phase is useful. then add a small amount of TEA to the carrier solvent.
Can you get your hands on some stains? Or Iodine? you would likely find these the most reliable.
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Awesome! The color issue should have been obvious but I’m just regaining my chops so thanks for the insight.
The kid is having issues getting solvent and you assume he just has a gc laying around!? Lol wtf
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I would order the solvent… you should just need etoac and hexane. Your boss should order this for you. Why wouldnt he/she order the solvents They are cheap.
I just stain with CAM or kmno4, there are several different stains that can be used to see your material, so just dip in stain and throw on a hot plate (this protocol is on the internet or any intro org lab text). You can also stain with 10%h2so4 and etoh or 10%hcl and etoh
I did not read this link but I think it should help.
Does this answer your questions?
Feel free to ask more questions
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Great link…thanks!
TLC kits linked there (and GCs and other options…)
Fast blue is commonly used for detection of cannabinoids. I’ve used chloroform as my mobile phase.
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I’m unsure why GC would be the go to suggestion - especially since its insanely more expensive than the analytical method that OP inquired about, which suggests OP doesnt want/cant buy a GC anyways. Also, GC cannot differentiate clearly between acidic/neutral cannabinoids because in vaporizing the analyte, it will all decarb and elute as THC neutral.
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most of us just watch the bubbles. decarb evolves CO2.
when the bubbles stop, you’re not making any more CO2…
if all you’re trying to do is separate THC from THCA, chances are you can use a sub-optimal solvent system. essentially anything that will dissolve them both & climb the plate.
so try ethanol and ethanol/acetic acid & report back!!
shadowing with UV should also work for detection. the plates reflect, and cannabinoids absorb. just like DNA (where I learned it)
I chatted with Hugh at SRI about this, and perhaps using their methanizer to detect the evolved CO2. He tried it for us. turns out there are other things evolving CO2 when you heat flowers 
I’m still not convinced it’s a bad idea…
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As soon as I get my s#$t together and get what I need I’ll report my results here.
I am also interested in doing this to see if perhaps the the process is leading to decomposition.
A heat plate and magnetic stirrer is just not optimal when the hot plate is putting out 350f temps and
causing wild temp swings on product if not monitored constantly.
Any experience in iodine chamber for TLC exposure…seems the simplest method.
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Are you concerned that chromatography is causing decamp? If so run a 2d TLC.
Spot the corner of a square TLC plate, run like a normal TLC, allow the plate to rest for 20-30 min (simulates the amount of time compounds would be on a column) and then run perpendicular to the first elution. If there is no decamp, all of your spots should be on the diagonal of the plate. If there is decomp, new compounds will appear off the diagonal.
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no. I don’t believe so.
OP wants to use TLC to monitor decarb.
to establish appropriate endpoint.
fast blue gives you way more data. and is pretty easy to obtain. unlike iodine
Like another user said Iodine can be hard to come by, but if you get some and want to try it:
Create a dispersion of iodine in silica gel. I don’t know the ratio but the silica gel should just be lightly brown/off-white.
After running the TLC and allowing the eluent to evaporate, rest the plate in the chamber for 5 to ten minutes. Don’t bury the plate or anything, the iodine in the atmosphere of the chamber is what stains the plate.
After 5 minutes the iodine will have colored the spots.
One cool thing about using iodine to visualize TLC plates is that it’s a reversible stain. so circle your spots with a pencil immediately. Once the spot coloration disappears you can use fast blue or something else to see if you missed any spots.