What Are Cannabis Nano-emulsions?
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Cannabis oils and water mix like, well, oil and water. But that has not stopped the CBD-infused drinks market, which is currently valued at $1 billion USD and expected to double by the year 2026.
So why does your CBD-infused sparkling water not come with an unpleasant layer of hemp oil floating on its surface? The secret is nano-emulsions. By suspending very small – just a couple of hundred nanometers wide – droplets of hemp oil in a drink, it is possible to evenly disperse the oil throughout the liquid.
But these emulsified cannabis drinks have a big problem: they can be very difficult for analysis laboratories to test. And in a world that generally lacks strict regulations on CBD products, sometimes there is very little cannabis in there to test at all.
How to make a nano-emulsion
There are multiple methods for creating a nano-emulsion that can be applied to cannabinoid oils, but one of the most common approaches involves the use of chemical additives known as emulsifying agents.
“One way that people get these cannabinoids into aqueous beverages is by encapsulating them with some kind of emulsification agent […] which is a molecule that has both hydrophilic and hydrophobic pieces,” Dr. Kristofer Marsh, lab director at The Niva Labs, previously told Analytical Cannabis.
“That hydrophobic part of the surfactant will basically connect to the cannabinoid, and the hydrophilic part will be facing out toward the aqueous beverage solution. In that way, you create these nano-emulsions.”
With the cannabinoid oil droplets now wrapped up in a more hydrophilic shell, they will become more miscible and dissolve throughout the beverage. Emulsification is also believed to help combat the usual poor stability and bioavailability of oral CBD in the gastrointestinal tract.
As an alternative method, some groups have experimented with using high pressure homogenization, where coarse emulsions are forced through a nanoscale valve at high pressure to break the oil droplets into even smaller parts, as a way to minimize the use of chemical emulsification additives. Last year, scientists from Pressure BioSciences reported that homogenization pressures up to 45,000 psi – over ten times the pressure used to homogenize milk – were able to effectively shear CBD oils into nano-emulsions.
Stability studies also revealed that the resulting nano-emulsions formed were reliably shelf-stable for at least 14 months when stored at room temperature and up to 18 months when refrigerated.
The challenge in testing CBD nano-emulsions
While the proliferation of cannabinoid nano-emulsions is good news for the infused drinks industry, these products do present some challenges for the analytical scientists who wish to carry out safety and potency tests on such beverages.
“[A drink can lining] typically has a hydrophobic coating,” Marsh explained. “And cannabinoids are themselves hydrophobic. So, when you put cannabinoids into a can, over time, eventually they stick to the sides of the walls.”
Naturally, if cannabinoids are stuck to the walls of the drink can, then they won’t be included when the drink is sampled to be tested or when a consumer drinks the contents of the can.
This tendency of emulsified cannabinoids to “stick” to hydrophobic materials can also cause problems inside testing apparatus.
“We have a lot of customers that are complaining about chromatography issues. They say ‘my columns are clogging, I constantly have to clean up my instrument, it works for one or two samples but then when I start to run more samples, I get those very strange and hectic results,’” Cristophe Deckers, an application scientist at Agilent Technologies told audiences at the Analytical Cannabis “The Science of Cannabis Testing” Online Symposium 2021.
“What's the issue here? It’s coating the columns, creating chromatography problems. And what's the solution? Well, we found that if you remove those oils, you remove those emulsifiers, the result is nice and robust chromatography.”
To do this, Agilent uses a Captiva EMR-Lipid filter kit during ordinary sample preparation, which is able to pull out many of the carrier oils and emulsifiers from beverages or other aqueous cannabis products being tested.
There are also some general challenges that are not unique to cannabis drinks, but that can still complicate matters during sample preparation. For example, many CBD-infused drinks are carbonated, and so testers may want to put their samples in a sonicator for half an hour in order to de-gas the sample so that it is easier to work with.
Is it all worth it?
Unlike cannabis edibles, which are largely marketed to existing cannabis users as a more convenient way to get high, cannabis beverages have made their splash in the general health and wellness market. CBD-infused drinks marketed as promoting wellness or relaxation have been quickly adopted by mainstream business in the US, although the smaller market for THC-infused drinks is also expected to grow significantly in coming years.
“I think right now it’s been more of a shock factor [with cannabis drinks],” Marsh said. “But I think there is certainly a market for it. I don’t think it will be the leading market. Things like kombucha and other sorts of wellness cocktails that aren't alcohol based […] they are popular. And I think that cannabis fits well into that market segment.”
“Bottom line, I do think it is worth the effort. I think there is a niche market, just like the mocktail market,” he said.
Overcoming the issues with testing these nano-emulsions in cannabis-infused beverages will be crucial in order to guarantee consumer safety and to foster an environment of transparency in this market. As evidenced by a recent investigation from Leafreport, the majority of well-known CBD drinks brands still suffer from significant disparities between the amount of CBD claimed on the product labels and the amount that is detected in independent laboratory tests. In extreme cases, some products were found to contain no measurable amounts of CBD at all.
While it is possible that some of these discrepancies could be due to the challenges involved in testing, it is clear that producers currently have some serious issues to solve in terms of product quality and stability. For consumers who are interested in trying out these infused beverages, the Leafreport investigation authors recommend looking for independent third-party certificates of analysis that can confirm the contents of the product.