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Variations in Cannabinoid Reporting

Hey everybody,

We’re doing a series of articles on cannabinoid reporting thanks to our good friends @marco and @savino!

What are your experiences when it comes to laboratory reporting?


It’s been all over the map. 13 to 24% for the same grow. When Washington state hired some consultants to develop their initial rules they found that testing of the same plant gave greatly different results from different labs. Is this a function of HPLC? The only reason for HPLC is supposedly because it can measure THCA. GC converts the THCA to THC. Who cares? Nobody cares about THCA anyway. Would GC testing be more consistent?


The inconsistencies you are referring to have as much to do with the growing and sampling for sending to the lab as the lab itself. Don’t misunderstand me, Labs make mistakes as well. But most labs know what they are doing and to be quite honest, most growers don’t really understand the natural variation that can occur from the top to the bottom of a single plant, under resource limiting conditions. And yes, even light is a resource. SO if you have 1000 watt light giving the top of your sea of green awesome light, but that sea of green is so densely packed that you essentially create shadow below the top of the but and the lower buds, or if you grow big tall plants in doors with great light above, all the middle and bottom buds will test between 5-10 percentage points (not percent) lower so a Kola testing at 28% might give you lower buds testing between 18-22 percent. How do I know this? cause we’ve done the measurements.

So honestly, how many kolas do you grow, and and how many times do you send not top, grade A buds to be tested at the lab? but now, when we have to test from random selection of a whole batch, suddenly the numbers change. And here is where a lab may not know what they are doing. If a lab takes in 5 grams but yet takes a single bud for testing potency, they aren’t doing you any favors. Without homogenizing the entire sample, so that its representative of the whole “initial 5 grams” and so that if a reprep is needed its done from the same representative sample and not some other randomly chosen bud that may have a different set of numbers because it was on a different part of the plant.

This also applies to concentrates, or maybe even more so, due to viscosity. Bringing in 1 gram of a 1000 gram vat of oil is not doing you any favors. and if you are testing your product before final form, or package ready form, then you aren’t getting the real answer, cause you can’t always assume things work the way the math would, due to homogenization problems, viscosity, degradation etc.

So it would be nice, if a dialog could be had so that the people who are so sure that the labs are getting wrong, actually aren’t getting it wrong themselves.


Are there any testing standards or recommendations for getting the average THC across the natural variation in the bud, for growers that want an accurate average for the plant as a whole?


Great response! Thanks a million Reggie.


It’s all about representative sampling, which means being willing to sacrifice enough to get the good data. If you look at the way things are done in the Ag industry, they take a SIGNIFICANT part of every batch, for testing. So, the sample they take is representative in a better way of the whole batch. Of course, wheat or corn are WAY cheaper than Cannabis per pound, so that becomes unattractive from the cultivators perspective.

But if you have a 10 pound batch, you should expect to have to have at least an ounce, taken by collecting multiple random samples from all portions of that 10 pound batch which would then be further subsampled to get the number of grams necessary for all the tests, and duplicate tests (the number of sample increments determined by the size of the batch; so a 1 pound batch would have fewer increments and lower overall sample weight taken than a 10 pound batch).

The subsampling is done by homogenizing, at least roughly the ounce (for a 10 pound batch) so that there were no pieces larger than a centimeter square or so, followed by thorough mixing, and then taking the necessary weight for each test being run, and having enough to do a second test from source if there are any issues.

The subsampled weight of Cannabis is then finely homogenized for lab testing, and then the weight for each test is taken from that whole subsampled, finely homogenized sample batch, so that it represents the entire subsample mixed together and that remainder after the initial tests is stored so that a fresh reprep from source can be done.

That’s how you, the cultivator, can be sure that you get more representative testing so that in States that are now starting to enforce batch variability standards, you get the right testing, and this approach works for edibles as well.


Great article. I look forward to part two. In Alaska we’re going through some THC testing inconsistencies also. Alaska requires batches be no more than 5 lbs with required testing for each batch. Samples are required to be random from each batch performed by the cultivator and is basically on the honor system . Recently Steep Hill Alaska bought two samples of 16 different strains of flower from retail locations around Anchorage and sent half to Canntest to be tested and retested the other half themselves. They then compared them and found a very large deviation in Total THC content. As I understand it, each lab uses HPLC equipment to test Cannabinoid content. Here’s a link to the recent story.

This has been big news in the industry as the legal market has only been up and running for about a year and a half. The legal industry relies on accurate testing to differentiate between legal and black market cannabis. It’s one of the main advantages the legal industry has over the black market, not the only advantage but an important one. In response the Alaska Marijuana Control Board (AMCO) has decided to form a “Testing Working Group” to recommend improvements to the testing regulations and procedures. This group is still being formed and is expected to come up with ideas and solutions to improve testing accuracy and present them to the Alaska Marijuana Control Board (AMCB) which has the authority to make changes. Here is a link to the AMCO announcement.

I’ve been contacted by Erika McConnell the director of AMCO through an email invitation asking for industry volunteers. I applied last week and today had a phone interview with Brandon Emmet an industry member of the AMCB who will chair the Working Group. I’ve made it to the short list, and hopefully l’ll get the opportunity to be in the workgroup if I make the final selection. I’d love any information on this topic and any suggestions by the Growers Network community. Thanks in Advance and I wish you all a Happy Holiday season!


That’s awesome Gary! We’ve got part two lined up really soon. :slight_smile:

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Part Two is up!


Part Three is up!