How do they measure THC levels in cannabis?

These days it’s not enough to simply have good weed as a dispensary or coffeeshop. More and more countries are legalizing cannabis so growers are able to better control their plants and test the product in a laboratory. This is necessary because people are getting more picky and want to know exactly what they are smoking. Next to that, in some places it’s only allowed to have a certain amount of THC in your product (like Canada)

Especially for medicinal patients it’s important to know whats in their medicine (It’s required when selling cannabis as a medicine).Thats why dispensaries and growers show the levels of THC and often CBD on their product. To do this it takes quite some knowledge and equipment. Thats why it always happens in a laboratory. But how do they measure THC levels in cannabis? Well you have more then one way to measure it:

Gas chromatography and  Liquid chromatography. 

This processes might sound overwhelming and difficult and yes they are, but the way they work is pretty easy to explain. One is more precisely then the other but both are populair and work fine for cannabis.These options are specific to measure THC, for CBD and other cannabinoids there are different methods. The substance THCA plays a big role in the measuring proces.

If you don’t know what THCA is click here to find out! 

Using liquid chromatography to measure THC in cannabis (HPLC)

More then half of cannabis tests are done by High performance liquid chromatography. Thats because it’s one of the most accurate methods and you don’t need any heating procedures to do it. Also you get levels of THC and THCA wich is also unique for this method.

HPLC is a way of analyzing each component in a mixture. It pumps a liquid with the mixture (Cannabis) with pressure through a column filled with a solid adsorbent material. By doing this you’ll won’t decarboxylate the THCA into THC so you get results of both levels.

The problem is that if cannabis get’s dried and smoked, the THCA will decarboxylate and turn into THC (so the thc levels will change). However not 100% of it will turn into THC so it’s hard to calcute what the final THC levels exactly are. To do this they have figured out a very precisely formule which calculates based on the molecular differences of THC and THCA:

THCtotal= (%THCA) x 0.877 + (%THC)

This is the most accurate way of measuring THC levels in consumed cannabis. A less accurate method but also often used is Gas chromatography. This method is a little easier to do.

Using gas chromatography to measure THC in cannabis (GC)

The proces of using GC to measure THC levels requires heat to do so. It is a method to analyze and seperate compounds in a substance that can be vaporized without decomposition (When it’s in the “gas/damp phase”).This method is not only used with cannabis, but also to measure the purity of different substances or simply spereting the compounds in a mixture to find out whats in.

When using GC on cannabis, you will use heat to decarboxylate the THCA in your fresh cannabis material. Onced turned into THC it will start to vaporate in your GC setup. This vapor will go through a detector that calculates how much THC is in the vapor.

We should be critical about these results though, because the heat you use in this method will only decarboxylate around 70% of the THCA (only 70% will turn into THC and go through your detector). So you won’t measure all THC thats actually in when consuming. Keep in mind that the real THC levels are probably a little higher.

Next to these methods there are some other scientific ways to measure the THC in your product. Also other cannabinoids like CBD or CBN and even terpenes can be measured by different methods (often chromatorgraphy methods). But for most scientists and consumers, THC levels are the most important. Thats what’s give you a psychoactive effect!

If you know other methods, or want to know more about a particulair method. Feel free te leave a comment below!



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