Testing for THC in hemp

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We folks at The Good Lab were concerned about SB17-090, a bill regarding how THC is calculated in hemp, and how it might negatively impact hemp producers if certain adjustments in the calculations weren’t considered.

So we wrote this email to the bill’s sponsors:

After reading SB17-090 regarding how THC is measured in hemp, we’re concerned that there is a calculation error that could negatively and unfairly impact hemp farmers. Simply adding THC-A and delta-9-THC together will not give an accurate or fair result. Considering that Amendment 64 specifies delta-9-THC, factoring in a correction value to account for decarboxylation is important.

Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO2). When THC-A is decarboxylated and converted to delta-9-THC, there is a reduction in the molecular weight that will affect the final percentage calculation. The molecular weight of THC is less than that of THC-A due to the loss of the carboxyl group.

At our lab, we calculate the delta-9 potential in hemp or cannabis using a factor of 0.877. I’ve attached a sample potency report so you can see how we make our calculations.

This article from High Times further explains the error in the current bill’s calculation and why you can’t simply add THC-A and delta-9-THC together to get the accurate number you’re looking for..
http://hightimes.com/grow/thca-vs-thc-how-to-read-a-lab-result/

We respectfully recommend an amendment to SB17-090 correcting this calculation error.

Apparently, the sponsors passed our concerns onto the Colorado Department of Agriculture. We were excited to get the following response from Mitch Yergert, Director, Division of Plant Industry:

This bill (SB17-090) only affects the testing being conducted by CDA at our lab. We have no desire to affect how the private labs conduct testing for hemp producers. We know most (if not all) of you use HPLC and will continue to do so. We were very specific in the bill to not require a certain piece of equipment or methodology to accommodate this and additionally our approach could change in future years to HPLC or even something else if a better type of machine comes along. We don’t believe the bill language would prevent this in the future.

Currently we use a GC for our analysis as it is more cost effective for the program and the hemp producers. Because of this we don’t have the issue with needing to calculate the THC-A conversion. We would recommend you use the 0.877 molecular weight value as the most conservative approach. We have seen some reports that actual yield from decarboxylation will be less than the exact .877 and that makes scientific sense. We have seen numbers as low as 0.700 in one study. But we don’t have sufficient data to select a specific number less than 0.877 that we would stand behind.

As your testing is not regulatory and we don’t base our regulatory decision on those numbers, by using the .877 number you are providing a conservative estimate to the grower which provides the highest potential THC for the crop. That seems to be the best number for the grower to consider. They can make the decision how to move forward with their crop based upon that. It is conceivable if they are minimally over in your testing using HPLC and the 0.877 conversion and we run a GC analysis, that the value could come in at 0.3 or slightly under, but that is good for everyone.

I believe the variability in sampling conducted by the grower versus CDA is probably a much bigger variable in the process than whether the private labs use HPLC and we use GC. So comparing the two numbers just based on the lab values may not be that productive.

What was really exciting was the validation we got from the CDA about the importance of private labs like ours.

The private labs perform a very valuable function for the hemp producers as the industry tries to get established. We appreciate you efforts to work with them and us on this issue.

We’re excited to work with the CDA, hemp farmers as well as other private cultivators to produce and develop high-quality hemp and cannabis products.

For more information on how The Good Lab might help you, please give us a call at (303) 455-3801.

Potency testing: GC vs. LC

Alex-Edwards-at-LP-Analytical-3At The Good Lab, we use High-performance liquid chromatography (HPLC) for potency testing. Why is that important? Here’s a great explanation of the difference between gas chromatography (GC) and liquid chromatography (LC) from Lift Cannabis News Magazine (Canada).

Potency Testing

Marijuana is a complex matrix. Like many natural products it contains thousands of compounds, many of which have yet to be discovered or understood. Separating out the THC and CBD from the diverse soup of compounds contained in your marijuana is essentially like looking for a few needles in a big haystack.

Chromatography is the chemist’s way of sorting out that haystack. In the cannabis world, potency is tested by liquid chromatography or gas chromatography. Although there are some promising techniques for testing potency using spectroscopy instead of chromatography, chromatography is currently the industry standard method used in Cannabis testing labs from Colorado to Uruguay.

How it works

To get an understanding of how chromatography works and what the “liquid” and “gas” terminologies mean, one first needs to look at the “column”. This is where the separation occurs in both liquid and gas chromatography.

A column is basically a tube that contains a chemical phase or material (the stationary phase) and a “mobile phase” which is what keeps everything moving through the column (this is where the “liquid” and “gas” part comes in). In gas chromatography the mobile phase is a gas (an inert gas like helium, hydrogen or nitrogen) and in liquid chromatography the mobile phase is a liquid (like methanol, acetonitrile and water).

For the separation to take place, the marijuana extract gets put onto the column, and will be transitioned through the column from one end to the other by the mobile phase. The components inside the extract (the THC and CBD) will have varying affinity to stay in the stationary phase that lines the column. Some will stay in longer than others, so they become separated from each other.

gc vs lc liftcannabis caAt the end of the column, once each of the components have been separated, they will be detected or “counted”. There are differences between the way the THC and CBD are detected between liquid or gas chromatography. In gas chromatography (GC) you often see that the analysis is called “GCFID”. The FID part stands for “flame ionization detector” which is essentially like it sounds – a flame! The FID will burn the compounds as they exit the column and an electrical signal is measured. This signal is directly proportional to the amount of the compound present.

In this type of liquid chromatography, the measurement is by UV (ultraviolet). A light in the wavelength range of the ultraviolet (yes, the same UV that your Oakley sunglasses are blocking from your eyes) is directed through the compound as it exits the column. The helpful characteristic of the THC and CBD molecules is that they absorb UV light, and this absorption can be measured and is directly proportional to the amount of the compound present.

You may have noticed that “LC” is often referred to “HPLC”. This was just the chemists adding more letters to something that was already concise and sensible. The “HP” stands for high pressure, or sometimes “high performance”, which varies from manufacturer to manufacturer. Some even call their systems UHPLC or ULTRA high pressure liquid chromatography. A higher pressure system will do the analysis faster, but that’s it.

So what about the other cannabinoids? Chances are, if you are reading this blog you are aware that there are a lot of other important cannabinoids in marijuana; CBN (cannabinol), CBG (cannabigerol), CBC (cannabichromene), delta-8-THC and many, many more! Why are these not reported? Especially as there is an indication that these compounds have important medical properties. Well, for now, it is not required. But many labs and licensed producers are already testing for these other cannabinoids. And what about the acid forms of the compounds, THC-acid and CBD-acid? This brings out an important discussion that relates directly back to the analysis by GC versus LC.

The effect of the main psychoactive compound (THC) is greatly reduced unless the THC-A is converted to THC. When cannabis is heated, the acid forms of the cannabinoids will readily convert to their neutral forms. Without heating (and not waiting for a long time) THC will remain in acid form, and this structure of the molecule doesn’t bind to the receptors in our brain that happily accept the neutral THC (THC with the acid removed).

Why does this affect the choice of analytical instrumentation? Well, in order for GC (gas chromatography) to work, the marijuana extract has to be converted to gas form, which means it is heated before entering the column. Any acid cannabinoid compounds, such as THC-A will be converted to their neutral forms, and no acid compounds will be detected, Conversely, in LC, the extract in liquid state can be injected onto the column as is, and therefore, you can quantify all the acid and neutral forms of your cannabinoids.

Some argue that the GC better mimics the state in which marijuana is typically consumed; by smoking or vaporizing. However, many patients may choose to vaporize at lower temperatures, and they may in fact be consuming some of the cannabinoids in acid form. And what about the potential medical benefits of the acid cannabinoids and the other unreported cannabinoids such as CBC? At this early phase in our industry, we at Signoto believe it’s better to provide as much information as possible to medical practitioners and patients. It’s time to move quickly away from the mystery era of cannabis.

~Emily Kirkham

VP of Laboratory Operations at Signoto.

Thank you Lift Cannabis News Magazine for allowing us to share this! Please visit their site for more information on all things cannabis in Canada.