Health & Wellbeing

Measuring vapor pressure of THC paves the way for reliable marijuana breathalyzer

Measuring vapor pressure of TH...
A team of researchers has developed a way to accurately measure the vapor pressure of THC molecules
A team of researchers has developed a way to accurately measure the vapor pressure of THC molecules
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THC molecules are larger and more complex than alcohol molecules leading to a great difficulty in producing a simple breath detection device
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THC molecules are larger and more complex than alcohol molecules leading to a great difficulty in producing a simple breath detection device
A team of researchers has developed a way to accurately measure the vapor pressure of THC molecules
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A team of researchers has developed a way to accurately measure the vapor pressure of THC molecules

As marijuana legalization sweeps through the United States there is a pressing need for an accurate roadside test for intoxication. The complexity of the primary psychoactive compound in marijuana is still proving to be a challenge for scientists trying to produce a straightforward breath test. A team at the National Institute of Standards and Technology (NIST) has recently made a major breakthrough in developing a new technique that can detect the presence of marijuana in vapor.

With one recent study by the Highway Loss Data Institute claiming the legalization of marijuana has coincided with an increase in road accidents, some lawmakers are becoming increasingly hesitant about passing new recreational laws. In May the governor of Vermont vetoed a recreational marijuana legalization bill, noting concerns over stoned driving and the lack of an "impairment testing mechanism."

Scientists face several challenges in developing a simple marijuana breathalyzer including the frustrating tendency for THC to linger in the body long after the psychoactive effects of the drug have worn off.

The more pressing fundamental difficulty in producing a functional marijuana breath test has been that the vapor pressure of THC molecules prove to be notoriously difficult to identify. Ethyl alcohol molecules have a high vapor pressure, meaning many molecules escape as gas when in liquid form. This is why it is easy to identify blood alcohol levels through the breath of an intoxicated person.

THC molecules are larger and more complex than alcohol molecules leading to a great difficulty in producing a simple breath detection device
THC molecules are larger and more complex than alcohol molecules leading to a great difficulty in producing a simple breath detection device

THC molecules on the other hand are larger and more complex with a low vapor pressure. This makes developing a measurement device that can identify THC in a person's breath incredibly difficult. The team at NIST tackled this problem by using a new process called PLOT-cryo.

"PLOT-cryo is an extremely sensitive technique for capturing and analyzing things in the vapor phase," say co-author of the study, Tom Bruno. "It was a natural candidate for this type of problem."

Invented in 2009, the PLOT-cryo system has been used to detect trace elements of explosives in airports and find buried bodies by identifying faint scents of decomposition in the air. In this study the NIST team successfully used the technique to calculate the vapor pressure of both THC and cannabidiol, a second, less psychoactive compound found in marijuana.

Despite this foundational technique, more research is still needed before we will see a reliable marijuana breathalyzer. An accurate understanding of how THC vapor pressure levels correlate with blood levels is yet to be researched. There also isn't yet an agreed scientific consensus over what level of THC in the blood constitutes a safe driving volume.

The NIST research certainly offers a strong scientific basis in a technique that can accurately measure THC levels in vapor, hopefully spurring further research that can produce an accurate and reliable marijuana breathalyzer in the future.

Source: NIST

3 comments
jerryd
They have the same physical performance tests that they use for alcohol. And all the studies I've seen has been a drop in accidents, especially fatal ones as people switch from hard drugs like alcohol, opioids, fake pot, etc to legal pot that no one has ever died from pot poisoning. And in the morning you wake up refreshed, not hung over or drugged out needing more.
ezeflyer
US Dept of Transportation study found small or no adverse performance of MJ on drivers. Look to the people who benefit from MJ prohibition for continued criminalization of users. https://ntl.bts.gov/lib/25000/25800/25867/DOT-HS-808-078.pdf
CzechsterMarek
The Big Pharma's supporters in Congress have thrown them a bone. It is amazing that employers do not require breath test for alcohol or prescription opioids but will jump at every opportunity to take a jab at marijuana. Alcoholics and Opioids addicts scare me far more than people who occasionally use marijuana. Over 45,000 have died due to prescription drugs and all I hear is the "Reefer Madness" beating the drums in Congress. To date no one has died using marijuana.