Legalization of recreational marijuana raises concerns about the possibility of drugged driving.
ANALYTICAL CHEMISTRY
ment. Finally, it is a challenge to make sensitive and specific roadside measurements. Scientists are trying to find markers that can be measured to reveal an individual’s marijuana use. Smoking and vaporization are the main ways marijuana users administer the drug. Studies have shown that blood concentrations are at their highest before a user has even finished smoking. Plus, there are psychological and physiological effects Instruments under development could become from the first puff, Huestis said. the marijuana equivalent of the breathalyzer Experienced users smoke differently depending on the potency of the marijuana, CELIA HENRY ARNAUD, C&EN WASHINGTON Huestis added. In effect, they “titrate” their dose. Plus, they can develop partial tolern the U.S., four states and the District “Breath has been an accepted sampling ance to some THC effects. But naive users of Columbia have legalized recremethod for law enforcement,” Lovrich said. who don’t yet know how marijuana affects ational marijuana, and many other Unfortunately, such devices don’t yet exist them may not know how to titrate their dose states allow medical use of marijuafor marijuana. and have no tolerance. Thus, occasional na. And the numbers are growing. AdditionAt a symposium on the analytical chalsmokers who drive after smoking may be al states will vote on legalization this year if lenges of drugged driving, part of the Pitts- more impaired than a regular user. their ballot initiatives garner the required burgh Conference on Analytical ChemisDuring metabolism, THC is oxidized signatures. try & Applied Spectroscopy held in Atlanta to form 11-hydroxy-THC, which is just as “The momentum is continuing to grow,” earlier this month, speakers described the potent as the parent compound, Huestis said Nicholas Lovrich, a marijuana policy challenges of developing such devices. For said. The primary metabolite in urine is expert at Washington State University. For example, developers need to figure out 11-nor-∆9-tetrahydrocannabinol-9-carboxylexample, in Washington, one state that has which compounds to measure and how to ic acid, otherwise known as carboxy-THC. legalized marijuana, marijuana stores similar detect them selectively. Plus, researchers One problem with using THC as a marker to liquor stores have opened. “Revenue has need to understand what the measureof recent marijuana use is that THC is stored been more than expected, and the problems ments tell them about how recently the in fat cells of chronic cannabis users. Chronless than expected,” Lovrich said. driver used the drug. ic smokers build up lots of THC, which But that doesn’t mean there are no probThe measurements are so difficult beleaches out over time. THC is measurable in lems. The uptick in use that accompanies cause of the low concentration in breath chronic smokers for as many as 30 days after such legalization can translate into an inof the primary psychoactive component, the last time they smoked, Huestis said. And crease in the number of impaired drivers, ∆9-tetrahydrocannabinol, better known it can found in the brain even when it’s not whom law enforcement officers want to as THC, said Marilyn A. Huestis, an expert detectable in the blood. keep off the road. who recently retired from the Other plant cannabinoids One way to catch them would be with National Institute on Drug such as cannabinol and cannabitests like the ones used to catch drunk drivAbuse. In addition, testers need diol and THC metabolites such ers. During traffic stops, police can get susto make sure they are collectas THC-glucuronide are better special report pected alcohol-impaired drivers to breathe ing breath instead of oral fluid markers of recent cannabis into a device that measures the percentage because wide variations in oral NEWS FROM usage, Huestis said. These canof ethanol in their blood calculated from the fluid concentration preclude its nabis markers appear rapidly in amount present in the breath. use as an indicator of impairblood and are only detected for
Working to help police detect drugged driving
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C&EN | CEN.ACS.ORG | MARCH 28, 2016
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a short time, well within the time frame of the cell. By scanning the compensation cannabis impairment. Unfortunately, these voltage, analysts can detect unknown comcompounds aren’t guaranteed to show up pounds. By picking a fixed compensation in everybody. Their presence guarantees voltage, they let only specific compounds recent use, but their absence doesn’t rule it through. out. But it may not matter because laws such One such instrument is being developed as Washington’s focus exclusively on THC. by Cannabix Technologies, a firm based in That state set a legal THC limit of 5 ng/mL. Vancouver, British Columbia, in collaboraSo tests for impaired driving have to fotion with Richard Yost’s lab at the Univercus on THC. And those tests need to show sity of Florida. The partners are developing recent use, said Brianna Peterson, a forensic a new instrument based on novel FAIMS toxicologist at the Washington State Patrol. cells, a planar one and a hemispherical one. Because the Washington State Patrol Toxi“Every component reflects new science, cology Laboratory is the only toxicology lab so it’s very exciting,” said Jared Boock, a for law enforcement in the state, it receives researcher in Yost’s lab. The team is still all blood samples related to impaired drivworking on a front-end breath sampling ing, she said. interface, he said. HO There are two levels Boock showed that H of testing for suspected they can detect THC in R impaired driving cases, simulated breath in 30 O Peterson said: screening seconds. But they can’t and confirmatory. The use samples from actual H goal of screening tests marijuana smokers beTHC is to eliminate negative cause pot is still illegal 9 samples. Any sample that R = CH3, 𝝙 -tetrahydrocannabinol (THC) in Florida. Instead, they gives a positive result in a R = CH2OH, 11-hydroxy-THC use small cigars, which R = CO2H, carboxy-THC screening test must then contain nicotine levels be analyzed in a confirmatory test to distinequivalent to the THC in five marijuana guish between true and false positives. cigarettes. They have successfully demonSince Washington’s ballot initiative strated the ability to detect nicotine and passed in 2012, the total number of cases cotinine in human breath. received at Peterson’s lab has increased Getting volunteers isn’t hard at Washfrom 5,298 that year to 7,044 in 2015. All the ington State University, said Herbert H. analyses are done from blood samples. In the Hill, a chemistry professor who is working most recent year, nearly one-third of samon developing a DMS-based THC detector. ples tested positive for THC. An even higher He asks volunteers to buy a specific brand percentage tested positive for the metaboof marijuana at either of the two local lite carboxy-THC. But even as the number cannabis shops. That brand, called Blue of positive samples has increased, both the Dream, contains about 23% THC, which mean and median THC concentrations have means that a typical 0.3-g dose delivers 70 decreased. And less than half of the positive mg of THC, he said. results were for levels above Washington’s He asks volunteers to smoke using whatlegal limit of 5 ng/mL. ever method they want until they achieve But such tests are run back in the lab. Law a self-diagnosed high of between four and enforcement needs tests that can be run in six on a 10-point scale. Each participant the field and followed by confirmatory lab provides breath samples of one-minute dutests. Alcohol breathalyzers involve an elecration taken before and after smoking. trochemical reaction. The leading contender Hill is collaborating with Chemring for a THC analog is ion mobility spectromeDetection Systems of Charlotte, N.C., to try (IMS), a technique that law enforcement develop the detector. At Pittcon, Jeffrey already knows thanks to explosives testing. Okamitsu, chief technology officer at CDS, IMS separates analytes according to said the firm is looking only at THC, not the time they take to traverse a drift tube its metabolites. CDS’s DMS chip acts like against a countercurrent gas flow. Rean ion filter and is more selective than IMS searchers are developing instruments using systems now on the market. To date, CDS’s variants of IMS called field-asymmetric instrument has been able to measure THC IMS (FAIMS) and differential mobility particles as small as 10 pg. spectrometry (DMS). Firms such as CDS and Cannabix could In both FAIMS and DMS, an electric hit it big. If marijuana legalization spreads field that alternates between high and low beyond the handful of states where it has voltages on the microsecond timescale is been enacted so far, detecting impaired applied to the analysis cell. An additional drivers and getting them off the road will potential called the compensation voltage become a chief concern for the law enforcecontrols which analytes make it through ment community. ◾ MARCH 28, 2016 | CEN.ACS.ORG | C&EN
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