Testing cannabis

[HippyLabRat]

I have reservations about using GC for testing Cannabinoid content.

CBD may degrade under heat to D9-THC... the terminal ene group and one of the phenols could collapse and form the fused ring under heat. This would inflate your %THC, and make your %CBD artificially low or non-existant.

Its part of the reason that you'd want to NOT smoke high-CBD flowers. When you burn it directly, you convert all of the medically superior CBD to THC.

[MichaelStuart]

Hi,

Thanks for your post. In all of my research, I have never some across anything that even mentioned CBD "degrading" under heat alone to THC. I would be quite interested in reading any info on this.

It was always my understanding that isomerizing CBD in to THC would require refluxing with acid, but heat alone?

I have also never noticed this effect when testing my cannabinoid standard which has 1000ug/ml of each CBD, THC, CBN.

Also, as far as burning your cannabis converting all of your CBD in to THC... hmmm... never heard of that either.

I look forward to learning something new. Thanks.

Mike

[HippyLabRat]

Its a completely intramolecular reaction. In a general sense, reaction probabilities favor intramolecular shifts first. Terminal enes are known reactive groups, and there are two symmetric phenols about an axis of rotation. Refluxing the CBD in acid will simply make the reaction temperature threshold lower before it converts.

I doubt there's any literature on it... who, until recently, would have studied or thought about it?

[MichaelStuart]

Hi,

I figured I'd throw another question out to the ether.. Part of the samples I am quantifying cannabinoids in are from edibles, baked goods, and tinctures. Some of the tinctures are Oil based (ie. Coconut oil, sunflower oil, etc.). Should I be concerned that these sample will gunk up my column, and/or greatly shorten the column's life? I do bake it out regularly, and I'm using glass wool in my liners. My procedure for baking out the column is to bring the temp up to about 325 C, and watch my FID signal until it stops detecting crud. Normally takes about 2-3 minutes. I really couldn't find any info online about proper bake-out procedures for my column (Restek RTX-5). It sort of leaves me hoping that I'm not damaging my column.

Any thoughts on the subject would be appreciated.

Another note.. I am pleased to report that it seems of my reproducibility problems (FID) have been solved once adjusting my split to 20:1, and employing the 7673 auto sampler.

Next challenge for me is to improve my peak shape on my second detector (ECD). My chromatograms look kinda ugly, and seem to have some drastic tailings. I have verified that the column install on that detector is all to spec. New gold seal, liner, septa, trimmed 15mm off column prior to installing it, and measured protrusion to 26.5mm from the base of column nut.

I'll post when I have an opportunity.

THANKS CHROMFORUM!!!

Mike

[Shralping]

Hippy lab rat,

You would imagine that the people who make cannabidiol (CBD) reference standards would think about it. Anytime you shoot CBD into a hot inlet
would lower the mg they sold you and also should give you a spike where THC should sit.
At that point you would be confused what they sold you when it was supposed to be only 1 component. The effect could be hidden among a reference standard that has multiple cannabinoids but not with a CBD only ref standard.

I doubt CBD to THC happens due to heat.. atleast at a scale to make enough difference to notice. Either that or a hundred labs are just saying nothing about it.

If it can be done, it would be because CBD is cheaper. Someone should have proven it. I have not seen any literature on this. Apart from maybe mention of acid type isomerisation.