Hemp or Marijuana?
Written by Rich Press   

THE NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY (NIST) has launched a program to help laboratories accurately measure THC and other compounds in cannabis products, including hemp and marijuana. The program aims to increase accuracy in product labeling and help forensic laboratories distinguish between hemp, which is legal in all states, and marijuana, which is not.

This article appeared in the September-October 2020 issue of Evidence Technology Magazine.
You can view that full issue here.

The Cannabis Quality Assurance Program (CannaQAP) is an interlaboratory study that will involve several exercises. In the first exercise, NIST will send hemp oil samples to participating labs, which will then measure the concentration of various compounds and report back to NIST. Future exercises will involve plant material, edibles, and other samples with complex matrices.

The Agriculture Improvement Act of 2018, also called the 2018 Farm Bill, legalized any cannabis material with a THC concentration below 0.3%. Below that number, it’s hemp. At or above that number, it’s marijuana, and illegal in many states and by federal law. A farmer’s crop can be destroyed based on that number, and interstate shipments can be seized.

“But many labs have limited experience making the type of quantitative measurement that the law now requires,” said NIST research chemist Brent Wilson.

Before the 2018 law, most crime labs determined if something was marijuana using the Duquenois-Levine test, a preliminary colorimetric test that indicates whether THC-like compounds are present, as well as a visual or microscopic analysis of plant features. The presence of THC could also be confirmed using GC-MS. However, while these tests indicate whether THC is present in the sample, they do not provide quantitative results. The law now requires concentration measurements and producing accurate and reliable numbers at levels as low as 0.3% can be a particular challenge.

Here’s how CannaQAP will work. In the first round of exercises, NIST will send hemp oil samples—all with the same, very carefully measured concentrations of THC, CBD, and 15 other cannabinoid compounds—to participating labs. Those labs won’t be told the concentrations of those compounds but will measure them and send their results back to NIST, along with information about the methods they used to do the analysis.

After collecting responses, NIST will publish the measurements the labs obtained. That data will be anonymized so that the names of the individual labs are not revealed. However, the results will show how much variability there is between labs. Also, NIST will publish the correct measurements, so each lab will be able to see how accurate its measurements were and how it performed relative to its peers.

“Anonymity means that labs don’t have to worry about how their performance will be viewed,” said NIST research chemist Melissa Phillips. “Our goal is to help labs improve, not to call them out.”

The NIST researchers will also assess whether some laboratory methods consistently produce better results than others. If so, they can recommend that labs adopt the better-performing methods.

Once that first round of exercises is complete and the data is published, which could take from six months to a year, NIST will run a second round of exercises. “We hope to see a tightening of the numbers the second time around,” Wilson said.

NIST is also planning to conduct future exercises with ground hemp and possibly marijuana, as well as edibles and other types of samples with complex matrices. Some of these samples may involve THC levels close to 0.3%, which will help labs determine the reliability of their measurements near this cutoff value.

NIST is also working on a hemp reference material—that is, a material that comes with known, accurate measurement values. Labs will be able to use that material to validate their measurement methods. One reason these measurements vary so much from lab to lab is that, currently, there are no reference materials for cannabis.

“Labs can accurately measure how much sugar is in your orange juice because they have standardized methods and reference materials for that type of product,” said Susan Audino, a chemistry consultant and science adviser to the Cannabis Analytical Science Program of the AOAC International, a group that establishes standard methods for laboratory analysis. “But cannabis has been a Schedule I drug since the ‘70s,” she said, referring to the Drug Enforcement Administration’s designation for drugs that have the highest potential for abuse.

NIST produces thousands of standard reference materials and has a long history of conducting quality assurance programs for improving measurements. Past programs have helped labs accurately measure compounds in dietary supplements, vitamins in human serum, and environmental contaminants in groundwater.

“Our goal is to support U.S. industries by helping labs achieve high-quality measurements,” Phillips said.

About the Author

Rich Press is science writer and public affairs specialist with the National Institute of Standards and Technology (NIST).

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