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New Handheld Scanner Can "Distinguish Hemp From Cannabis"

By Alexander Beadle

Published: Feb 14, 2020   
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When the 2018 Farm Bill was passed by the US government, the hemp industry rejoiced. The wide-reaching agriculture bill formally legalized hemp at the federal level and included provisions for the crop’s legal cultivation, transport, and sale.

But since the passage of the Farm Bill, those who transport hemp material across state lines have had a bumpy ride.

Farm Bill or not, truck drivers transporting hemp have been stopped and even arrested by local law enforcement who don’t have the proper tools to verify whether the plant material they see in a truck is legal hemp or federally illegal cannabis. And even if the responding officers have been issued with a narcotic identification kit, these kits are only able to give confirmation as to whether a plant contains tetrahydrocannabinol (THC) or not. Since hemp is legally defined as a cannabis strain containing less than 0.3 percent THC, these kits are almost wholly unsuitable for the purpose of differentiating hemp and cannabis material.

Now, inspired by the stories of these drivers, researchers at Texas A&M University have reportedly developed a “hemp scanner” that could be used by police forces to distinguish between hemp and cannabis, without damaging any of the cargo.

Adapting Raman spectroscopy to test cannabis

In a paper published in the journal RSC Advances in January, the Texas A&M researchers demonstrate that Raman spectroscopy is an effective, non-invasive, and non-destructive way to quantify the amount of tetrahydrocannabinolic acid (THCA) in plant material. From this reading, it’s possible to determine whether the plant would legally be considered hemp or not.

Raman spectroscopy is a non-destructive chemical analysis method, which is able to provide detailed information about the chemical structure of a sample. The method relies on the small variations in frequency that occur when light interacts with the different molecular vibrations of chemical bonds. Through studying the data gathered about these vibrations, it’s possible for analytical scientists to characterize unknown compounds and to detect and quantify known compounds.

The researchers at Texas A&M had previously been using Raman spectroscopy to devise quick, non-invasive tests for plant diseases and screening for the nutritional content of food, utilizing handheld Raman spectroscopy apparatus to do so. In a similar fashion, the researchers then set out to discover whether this apparatus could also be an accurate tool for analyzing cannabis.

The group used buds from 5-10 fresh hemp plants and 10-15 fresh-frozen cannabis plants which had been confirmed to be hemp and cannabis respectively by a third-party testing laboratory. Samples from these buds were then analyzed using a handheld Raman spectrometer, and the resulting spectra statistically analyzed in order to identify the spectral regions that could best illustrate the difference between hemp and cannabis.

The researchers found strong “fingerprints” (spectral marks) in the Raman spectroscopy data at around 1623–1660 cm-1 that correlated with the presence of THCA. They also observed a peak in the spectra at 781 cm-1, which could be attributed to THCA, and an additional band between 1260-1320 cm-1, which corresponded to both THCA and cellulose.

Interestingly, the researchers also discovered that the hemp plants contained a higher content of carotenoids and cellulose than seen in the cannabis species studied.

In total, the researchers identified seven regions of the Raman spectra where cannabis and hemp differed significantly, and when factored together they found that it was possible for the Raman apparatus to distinguish between hemp and cannabis with 100 percent accuracy.

Moving from the lab, to the roadside

With the principle of their method proven, the research group is now hoping to collaborate with industry players who could help to mass-produce a version of this hemp scanner.

Dmitry Kurouski, an assistant professor of biochemistry and biophysics at Texas A&M, and the lead author of the new study, has said that he believes mass production could feasibly start within the next two or three years.

In addition to being a useful tool for law enforcement, the study done by Kurouski’s team also indicated that Raman spectroscopy could be a helpful tool for hemp cultivators, who might wish to monitor their crop’s THC levels while they are still growing, to avoid cultivating any high-THC ‘hot hemp’ that cannot legally be sold or processed.

“These results suggest that RS [Raman spectroscopy] can be used for quantitative prediction of the THCA content in intact plant materials,” the researchers wrote in the study. “However, more experimental work is needed at this point to determine the accuracy and the range of THCA prediction. This work is currently in progress in our laboratory.”

Early tests also showed promise at distinguishing between different strains of cannabis and hemp, with one statistical model able to correctly assign 84 out of the 86 spectra taken to their correct classifications.

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

The team has also begun working towards devising a similar test to monitor the cannabidiol (CBD) levels present in different varieties of cannabis and hemp. This could be useful to cultivators who may want advance knowledge of how much their crop might be worth to the CBD industry. 

Alexander Beadle

Science Writer

Alexander Beadle has been working as a freelance science writer since 2017 and has covered the cannabis industry for Analytical Cannabis since 2018. He has also written for our sister publication, Technology Networks, and the cannabis industry consultant firm Prohibition Partners, among others. Alexander holds a Master's in Materials Chemistry from the University of St. Andrews, where he won a Chemistry Purdie scholarship, and conducted research into zeolite crystal growth mechanisms and the action of single-molecule transistors.


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