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Scanner measures level of THC in cannabis

Is it hemp or marijuana? A handheld spectrometer gives hemp farmers an instant answer.

A team of Texas A&M AgriLife researchers utilised a commercially available handheld Raman spectrometer. The team created spectral libraries to distinguish hemp and marijuana, and saw that the spectrometer can now be used as an accurate, instant THC scanner.

Hemp is technically legal in Texas, but proving that hemp is not marijuana can be a hurdle, requiring testing in a licensed laboratory. So, when a truck carrying thousands of pounds of hemp was recently detained by law enforcement near Amarillo, the driver spent weeks in jail awaiting confirmation that the cargo was legal.

Handheld spectrometer as a “hemp scanner”

Stories like that one inspired a team of Texas A&M AgriLife researchers to find a way to use a handheld spectrometer as a “hemp scanner” that could easily fit in a police cruiser and distinguish hemp and marijuana instantly, without damaging any of the product. The study was published in January in the scientific journal RSC Advances.

Value of hemp has skyrocketed

Both federal and state restrictions on hemp have loosened in recent years in the U.S. As a result, the value of hemp has skyrocketed, said Dmitry Kurouski, Ph.D., assistant professor of biochemistry and biophysics at the Texas A&M University College of Agriculture and Life Sciences, who led the study.

Texas farmers wanting to grow valuable hemp plants need a way to know that the plants contain little to no THC. When hemp can be legally grown in Texas later this year, producers will want to know if their plants’ THC levels are approaching 0.3%, which would classify the plants as marijuana and therefore illegal to have and grow.

Raman spectroscopy

Kurouski’s lab was experienced in using a technique called Raman spectroscopy to create quick and noninvasive tests for plant diseases and foods’ nutritional content. The technique uses harmless laser light to illuminate structures within materials. Each material’s scan is unique, akin to a fingerprint.

Kurouski had a hunch that Raman could be used to create a quick and accurate test for THC.

Dozens of samples of marijuana and hemp were tested using the spectrometer. A statistical analysis method found seven regions in the spectra that differed slightly among marijuana and hemp varieties tested, a high-tech version of the “spot the difference” brain teaser. Taken together, the readout in these seven regions distinguished the hemp and marijuana varieties tested with 100% accuracy.

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  • Dmitry Kurouski (left) and lab member Lee Sanchez (right) at the greenhouse of a Colorado farm that collaborated on the hemp scanner. - Photo courtesy of Dmitry Kurouski

    Dmitry Kurouski (left) and lab member Lee Sanchez (right) at the greenhouse of a Colorado farm that collaborated on the hemp scanner. - Photo courtesy of Dmitry Kurouski

  • Testing dozens of samples of marijuana and hemp fell to Lee Sanchez. - Photo courtesy of Dmitry Kurouski

    Testing dozens of samples of marijuana and hemp fell to Lee Sanchez. - Photo courtesy of Dmitry Kurouski

“We know plants from A to Z in terms of their spectroscopic signature,” Kurouski said. “But when we saw such a crystal-clear picture of THC that appeared in one second of spectral acquisition, that was mind-blowing.”

Now that Kurouski’s team has demonstrated its quick, noninvasive test for THC, they are looking to collaborate with industry to make their test available to the public.

Similar test for CBD

The team also aims to create a similar test for CBD. Farmers looking to grow hemp may want to know the amount of CBD in their plants to better estimate their value.

Read the full story on the Texas A&M AgriLife website.

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