Is it hemp or marijuana?

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. 

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.

Hemp’s Heyday

In 2019,
Texas lawmakers made a distinction between hemp and marijuana based on the
level of THC, or tetrahydrocannabinol, in a plant. THC is the major
psychoactive agent in marijuana. If a plant has less than 0.3% THC, it is
designated hemp. 

Both federal
and state restrictions on hemp have loosened in recent years. 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. Hemp is rich in compounds that are prized for their medicinal properties
and flavor. The most well-known is CBD, or cannabidiol, which is thought to
help with pain, anxiety and depression. 

But farmers wanting
to grow valuable hemp plants need a way to know that the plants contain little
to no THC. Texas producers need 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. An easy test for THC would be a boon for farmers as
well as for law enforcement.

Could an Existing Scanner Work?

Kurouski said
that the catalyst for using the portable scanner was his colleague David
Baltensperger, Ph.D., professor of soil and crop sciences at the Texas A&M
University College of Agriculture and Life Sciences. Baltensperger had worked
with both farmers and police officers and knew about the demand for a better
test for THC, Kurouski said. 

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. A
portable Raman scanner had been utilized for previous studies by lab members
Lee Sanchez, a research assistant, and Charles Farber, a graduate student.

What was then
needed was a way to scan many marijuana and hemp plants in order to search for
patterns in how their Raman spectra differed.

Fingerprinting THC

Testing
dozens of samples of marijuana and hemp fell to Sanchez. The testing needed to
happen near Denver, where recreational marijuana is legal.

“Lee Sanchez
was the hero who was traveling to Colorado three times, staying there in hotels
and driving from one location to another. Most of those locations are old fire
stations. They are not fancy greenhouses but old, shaky buildings with plants
inside,” Kurouski said.

Back in
Texas, Sanchez and Kurouski analyzed the collected spectra. 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.

“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.”

What’s Next?

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. 

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. 

The study
also demonstrated the ability to use the scanner to differentiate varieties of
marijuana. In the changing legal landscape, there are thousands of varieties of
cannabis, many of questionable quality. 

“Our
colleagues, the farmers, were positively surprised that we could identify the
variety with 98% accuracy,” Kurouski said. “That blew them away.”

Fearless on Every Front

A community
of scholars driven to create positive impacts around the world, Texas A&M
University embraces determination, innovation, and creativity.

Texas A&M
is one of the largest
research universities in the United States and is one of only 17 institutions in the
nation to hold the triple designation as a land-, sea-, and space-grant
university. Our faculty-researchers generated more than $952 million in
research expenditures in FY 2019, all while enhancing undergraduate and
graduate education by providing hands-on research.