Testing cannabis impairment at the roadside is arguably non-viable. Companies use various strategies to detect THC and THC metabolites. However, state-of-the-art processes are not currently faster than conventional methods.
Testing THC on the roadside
Classic roadside tests use a physical exam and a police officer's assessment of the driver, known as the Standard Field Sobriety Test (SFST.) Otherwise, officers use modern analytical devices that test body fluids for THC or THC metabolites. Impairment is challenging to quantify, though. The plant's intoxicating ingredient, tetrahydrocannabinol (THC), is lipophilic and stays in the body much longer than the impairment itself.
Dr. Evan Darzi, co-founder and CEO of ElectraTect, holds a Ph.D. in Organic Chemistry and spoke to Uprooted Concepts to discuss the viability of breath.If you're testing urine or blood or hair samples, even saliva samples, the time windows that indicate a positive result that somebody has THC in their system can kind of range up to 48 hours to several weeks after impairment. And there is a poor correlation to the timeframe of four to five hours in which a person would be intoxicated.
If you’re testing urine or blood or hair samples, even saliva samples, the time windows that indicate a positive result that somebody has THC in their system can kind of range up to 48 hours to several weeks after impairment.
So we’re not actually testing if somebody’s actively impaired at the time of testing, and this can lead to all kinds of issues — false prosecution, loss of employment, and even imprisonment in some cases. — Evan Darzi, Ph.D.
Detecting breath
Blood and oral fluid, classic bodily fluids collected by officers, are insufficient due to THC’s disposition time. Methods used to collect blood by injection, or spit by mouth swab, are also invasive.
Our initial goal was to see that breath is a better medium than traditional body fluids. And then it was just backing out what kind of tech would be the best for breath testing. So the obvious analogy was to look at how an alcohol breathalyzer works and see if we can develop some chemistry and materials that can act as a plug-and-play sensor. — Dr. Darzi.
ElectaTect’s breathalyzer for THC compares to conventional breath testing devices for ease of detection. But the chemistry is wildly different.
If we harken back to an alcohol breathalyzer, what’s happening in that system is you blow ethanol into this sensor. A chemical reaction happens, an oxidation reaction. Ethanol oxidizes to acetic acid, so basically, vinegar.
That’s a four-proton and four-electron process that generates a current. And then, the amount of current is proportional to the amount of ethanol going through that sensor. Ethanol is much more volatile, so it comes out in your breath in a higher quantity. And it’s a much smaller molecule so that less side oxidation can happen. — Dr. Darzi.
Making use of THC oxidation
Cannabis breathalyzers run into problems. Compared to alcohol, THC is a larger molecule consisting of functional groups. The molecule is, therefore, prone to oxidation. While ElectraTect’s device is arguably too slow for reliable roadside use at this time. Their device utilizes oxidation and creates colourful cannabinoid quinones with electricity.
The first thing we needed to figure out was a clean oxidation at only one predictable site. And a [reaction] that was going to lead to some change either in the electronic or colour — optical properties.
Our original idea was to develop oxidation chemistry. So we took to the literature to look at the THC molecule and hypothesized that this chemistry would work with THC. — Dr. Darzi.
Roadside convenience
Saliva test mechanisms, such as the Dräger DrugTest® 5000 and Abbott SoToxa systems, come with operational limitations. The time it can take an officer to run an analysis can extend ethical concerns. Defence lawyers suggest that a person should not be held for inspection before a positive result for longer than eight minutes. ElectraTect does not necessarily, however, provide a solution with a shorter operational procedure.
We intend to develop our breathalyzer to work within 5 to 10 minutes. You want it to be something practical for portable and rapid use, and you want it to be non-invasive. There are a couple of other companies that are working on this, one based in Vancouver and another based in California. It is unclear whether either of these technologies will be applicable for roadside use. — Dr. Darzi.
Quinones and electricity
Breath travels to a novel sensor in ElectraTect’s device that utilizes colourful cannabinoid conversions and their associated electrical signals, which detects the flow of electrons generated in oxidizing THC to colourful cannabinoid quinones. They were inspired by Raphael Mechoulam's work.
[He] was interested in the medicinal applications of cannabis quinones synthesized using chemical oxidants. We're able to confirm that we can make this compound. And then, we went to our electric chemical setup to see if we could make this reaction work just using electrochemistry, excluding the chemical oxidant altogether.
And we're able to see that we can basically take up to 70% of our starting THC and rapidly oxidize it to the corresponding quinone, confirming that we see a colour change. When you form these quinones, they typically have this nice red chromophore, which results in that red color. — Dr. Darzi.
THC fuel cell
The conversion to cannabinoid quinones produces energy, which ElectraTect captures and measures in breath samples.
In this example, we’re putting in electricity to make this chemical reaction happen. But, to make this like an alcohol breathalyzer, we need to develop a catalyst that will make this happen spontaneously inside our sensor. And then we can measure the electricity coming out. — Dr. Darzi.
The conversion from THC to quinone produces a quantifiable electrical signal.
So if I have a minimal amount of THC, I have a low electronic signal. If I have a lot of THC, I would have a large electronic signal. We can engineer this fuel cell sensor to use THC as the fuel. And now we see THC goes in, and then the quinone comes out. We're able to generate current off of that. — Dr. Darzi.
Detection Limits
Their device utilizes a correlation between the current generated and the concentration of input THC going into the reaction.
We made the first analogous sensor used in an alcohol breathalyzer, but now we made that sensor specific to THC. — Dr. Darzi.
Blood alcohol content drops off equivalently to impairment. Unfortunately, THC use is not easy to quantify. ElecraTect confirmed that more research is required to quantify THC effectively on the roadside.
Lots of people want a THC version of the Blood Alcohol Content. But we just don't have the scientific data to pin that down at this point. That's kind of still up in the air. Several clinical trials have shown that THC stays on your breath — have relatively small sample sizes. — Dr. Evan Darzi, Co-Founder and CEO, ElectraTect.
Current state-of-the-art detection methods that rely on blood, urine, and saliva are simply not practical for roadside detection. Despite the state-of-the-art analytical tools on hand, though, the detection times for cannabis use are often too narrow. Furthermore, chronic cannabis users have a baseline blood THC level above the legal limit for a month following abstinence. Breath is an alternate medium for cannabis detection, but not without limitations.
New technology and scientific discoveries are needed to find a selective, cheap, and portable device to bring fairness to traditional testing methods. But do you agree with the viability of roadside THC analysis concerning impairment from the respective terpenes.
This post was updated on December 15, 2022.
Sources
Communication with Dr. Evan Darzi, Co-founder of ElectraTect. 2022.
Huang, D., Forbes, C. R., Garg, N. K., & Darzi, E. R. (2022). A Cannabinoid Fuel Cell Capable of Producing Current by Oxidizing Δ9-Tetrahydrocannabinol. Organic letters, 24(37), 6705–6710.
Darzi ER, Garg NK. Electrochemical Oxidation of Δ9-Tetrahydrocannabinol: A Simple Strategy for Marijuana Detection. Org Lett. 2020;22(10):3951-3955. doi:10.1021/acs.orglett.0c01241