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How Do I Separate CBN From a Mixture of Cannabinoids?

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In the last few years, most of the attention in the medicinal cannabis market has been on CBD (which doesn't have THC) and, to a lesser extent, THC. But the market is changing, and people are becoming more interested in what are called “minor cannabinoids.” This post will be all about CBN Isolate Bulk.

CBN is made when THC breaks down, so cannabis plants only have very small amounts of it. By exposing it to light, heat, or air, or by using enzymes, THC can be turned into CBN. CBD can also be changed into CBN with the help of iodine (Federica Pollastro, 2018).

There will be contamination from THC/CBD and other co-extracted compounds that haven't reacted yet, whether this happens naturally through oxidation or chemically or enzymatically.

But How Do You Tell The Parts Apart?

Since pure CBN Isolate Bulk is a solid, it is possible for it to crystallise (Merck, 1989). Flash chromatography, on the other hand, has shown itself to be a more effective and efficient way to purify.

Most of the time, simple methods like reversed-phase flash chromatography are used to clean cannabinoids. But, as we've already said, the reaction from THC or CBD to CBN Isolate Bulk can make a lot of unwanted substances, which can make purification hard.

Reversed-phase may be all that is needed to turn a dark brown crude into clear, semi-crystalline CBN, depending on how pure the raw material is.

But if your crude is hard to clean up with reversed-phase chromatography, you can use normal-phase flash chromatography instead. In normal-phase flash chromatography, a silica column and organic solvents, such as hexane and ethyl acetate, are used. This method is needed to clean CBG, and it turns out that it can also be used to clean CBN.

So, How Do You Make a Normal-Phase Flash Method That Works?

Thin-layer chromatography (TLC) is the first thing I do to test different solvent combinations and ratios. For cannabis extracts, you can use hexane with ether or hexane with ethyl acetate. I mixed hexane with ethyl acetate instead of ether because it is safer (due to its higher boiling point, lower volatility, and higher flash point). Because these compounds can be dissolved in hexane, they need a mobile phase that is not very polar. I found that a mixture of 3% ethyl acetate and 97% hexane as a TLC solvent was enough to separate CBN from other impurities.

TLC data from my crude CBN reaction mixture, which included a hemp extract with mostly CBD and an aged cannabis extract with mostly THC, show that CBD, THC, and CBN are the substances that come out first. Even though the separation isn't very big, it's enough to clean up on a silica flash column under the same conditions.

For Flash Chromatography

I used a 10-gram Bona Voluntate and programmed an isocratic method (3% ethyl acetate/97% hexane) with detection using mass settings m/z -309 and m/z -313 (negative ionisation), m/z +311 and m/z +315 (positive ionisation) (positive ionization). I chose mass detection to make sure I was finding and collecting CBN, which has a different molecular mass (310) than CBD and THC, which both have a mass of 314.

Using the more sensitive negative ionisation mode, my results showed that this method was able to separate and collect Wholesale CBN Isolate (detectable m/z-309) from the other mass-detectable by-products.

I also used normal-phase flash chromatography with the same method to test the aged cannabis and hemp extracts. The order of the results matches the order of the TLC results.

I put all of the Wholesale CBN Isolate fractions together, let the solvent evaporate, redissolved the mixture in methanol, and used my reversed-phase method to check that the CBN I had collected was pure. So, a single peak with the right molecular mass for CBN was found.

So, if reversed-phase chromatography doesn't work and you need to make and purify/isolate Wholesale CBN Isolate, normal-phase flash chromatography is a good choice.

For more information about flash chromatography, you can read our whitepaper, Flash Chromatography Methods for Isolating Cannabinoids.

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