Most Cannabis Labs Correctly Test THC and CBD in Hemp Oil, NIST Study Finds
The majority of cannabis testing labs in the US appear to correctly quantify the amount of THC and CBD in hemp oil products, according to a new report from a federal agency.
The report from the National Institute of Science and Technology (NIST) is the first data release from its ongoing Cannabis Quality Assurance Program (CannaQAP), an initiative launched last year to help commercial and forensic labs agree on the techniques, technologies, and reference standards used to test hemp and marijuana.
Testing the testers
For the first stage of their program, the CannaQAP team sent hemp oil samples to 116 labs. The oils contained specific concentrations of THC, CBD, and 15 other cannabinoids, which the labs had to accurately quantify.
And, indeed, it seems most labs did just that.
“In general, the community values and the NIST target values did compare well with significant overlapping in their tolerance ranges,” Brent Wilson, a research chemist at NIST and member of its CannaQAP, told Analytical Cannabis in an email.
The majority of the participating labs gave THC and CBD results that were within an acceptable range of the NIST value. For example, one hemp oil sample consisted of 4.31 percent CBD; most labs reported values close to this figure, such as 4.31 percent, 4.22 percent, and 4.19 percent. Just eight labs reported a figure well out of range, such as 3.067 percent, 4.893 percent, or, in one extreme case, 20.8 percent.
“The individual laboratories did have variation,” Wilson said. “The possible reasoning for the variations could be associated with how the calibration was performed. Typically, laboratories will use calibration curves ranging 2–5 orders of magnitude, which can have an increased measurement uncertainty with it.”
This level of uncertainty seemed to increase when labs were tasked with testing for more obscure cannabinoids, such as THCV and CBDVA.
“It was more difficult to make comparison with the more obscure compounds as they are presence in the hemp oils at much lower levels, especially including the acidic cannabinoids as the oils were decarboxylated,” Wilson added. “However, I do think it does provide the participating laboratories a good opportunity to evaluate their methods with other results and see how other methods might be able to measure cannabinoids at lower levels then their analytical method.”
All labs with diverging results have already been contacted by the CannaQAP team and advised that their methods could be improved. But which improvements are needed will depend on where the method went wrong. A high calibration curve could be to blame for some inaccuracies, according to Wilson, but other oversights have yet to concluded.
“Due to the overwhelming labs using LC-UV [liquid chromatography-ultra violet light] and LC-PDA [liquid chromatography-photodiode array mass spectrometry] a true comparison between analytical methods is challenging,” Wilson told Analytical Cannabis.
“Even though a lot of the laboratories used different specific conditions (i.e. mobile phase) […] they’re still very similar.”
Wilson and his team hope that the second phase of the CannaQAP will reveal more about which methods are best suited to cannabis testing. This second phase launched in January and asked labs to test solid marijuana and hemp samples, materials that could be tested by a wider range of methods.
“In Exercise 2, we had more laboratories using different methods like GC-MS [gas chromatography-mass spectrometry], LC-MS/MS, etc. to permit a better evaluation,” Wilson added.
What’s next for NIST?
Wilson and his team are currently analyzing the results from the second phase of the CannaQAP, which required labs to test cannabis and hemp samples for cannabinoids, moisture content, and 13 toxic heavy metals.
“The final report of Exercise 2 won’t be available until 2022 most likely,” Wilson said, “but participants have been provided the preliminary data and certificates that will allow them to evaluate their performance in the meantime while NIST works on the final report.”
As for the third phase of the project, interested labs should expect an announcement within the next few weeks.
“An announcement for Exercise 3 should hopefully be coming in the next month as we are finalizing the targeted samples and analytes,” Wilson added. “But overall we are looking to provide participants of both Exercise 1 and 2 the opportunity to evaluate their methods again and to see if any improvements are recognized.”
In the long term, the CannaQAP team also hope to produce a set of cannabis reference materials that the whole cannabis industry (and all forensic labs) can rely on.
“NIST [does] not currently have a reference material available,” Wilson told Analytical Cannabis earlier this year. “We’re working on that for a hemp plant material that will probably be [available] early 2022. But in lieu of that, we’re giving [labs] more than enough material […] to help carry them over until that reference material would be available.”
“We’re thinking years out in advance,” he added. “This time next year, maybe we incorporate an oil sample back in, or we incorporate some type of edible or an extract. All that ties into our plan of building a reference material profile, to provide testing laboratories and forensic laboratories the necessary tools they need.”
