The joint relationship between chromatography and cannabis

To put it bluntly, you cannot have quality cannabis products without performing proper purification of the cannabinoids. In this blog post, I discuss how you can use flash chromatography separate THC and CBD from cannabis extracts. I also offer some advice if you are using the technique for pesticide removal. Read on and enjoy.

We’ve said goodbye to April, strange one as it was, but not before celebrating a few holidays, such as Easter, Earth Day and…4/20 Day or National Weed Day. Yes, this holiday exists, and it is celebrated on April 20th every year by all fans of the cannabis culture.

Well, I got interested in the origins of this celebration and read up on the topic. There are a lot of urban legends about why Weed Day is celebrated on 4/20. One of the most popular theories is that back in 1971, a couple of students, disinterested in popular extracurricular activities, met at 4:20 p.m. by their campus’ statue of chemist Louis Pasteur to partake. They would say “420” to each other as code for cannabis. The group Grateful Dead and eventually High Times magazine got wind of the term and popularized 420 worldwide.

I really liked this story. Especially because the group of students obviously recognized the importance of science for cannabis, as they met by Louis Pasteur’s statue! And oh boy, if you are interested in cannabis, you better be passionate about chemistry.

No matter the reason you are interested in cannabis processing, chromatography is an essential part of the workflow. Coincidentally, we just hosted a webinar covering the entire 10 steps needed to get to pure CBD from cannabis that you can access for free.

In a standard workflow, right after cultivation, extraction and concentration comes none other than purification. After the extracts are concentrated, you need to separate the cannabinoids from the complex resulting mixture. Flash chromatography is a suitable technique for purification of different compounds, such as CBD or THC, of the cannabis extract from each other. Importantly, flash chromatography can also be used to remove unwanted substances, such as pesticides, from the extract.

How can you perform flash chromatography with cannabis samples?

Very briefly, you apply the cannabis extract, often diluted 1:1 with ethanol directly to a stationary phase in a cartridge . As the mobile phase travels through the stationary phase, the compounds remain for shorter or longer periods of time in the cartridge. You then elute the desired substances, such as CBD or THC, into separate vessels. Keep in mind, the substances are still diluted with mobile phase in the chromatography system . To obtain pure compounds, you should further evaporate the solvent with a rotary evaporator .

The purity of isolated cannabinoids after flash chromatography typically ranges between 92-98%.

You can achieve higher purity by performing a second separation on a prep HPLC column or performing recrystallization methods.

How much cannabinoids you can get out after purification is highly dependent on the extract and the concentration of cannabinoids in the sample. With good conditions, you can process up to 200 g in 30-120 minutes.

And I’ve got a few tips if you are using chromatography for pesticide removal. There might be many different types of pesticides in your cannabis extract. Some might be more challenging to remove than others. If the polarity of the stationary phase is similar to the polarity of the target molecule, you might need to perform several flash chromatography runs or use preparative HPLC columns.

If you are interested in more information on purifying cannabinoids, as well as other processing steps of the workflow, check out our “Right Hand Book for Cannabis Scientists”. The booklet is especially focused on rotary evaporation and purification, two techniques that are also blog-favourites. I hope to have left you on a high with this post and see you soon!

Till next time,

The Signature of Bart Denoulet at Bart's Blog