Marijuana.com

Hashishi

Something in the air, man
8-13-'07 | SpectroscopyNow.com | by Steve Down

Marijuana continues to be smoked all over the world, despite new health warnings regarding its effects on the body. A study published this year found that smoking one joint can restrict the air flow to the lungs by as much as five cigarettes, while long-term pot smokers also develop asthma and bronchitis symptoms and excessive lung inflammation. Marijuana use also increases the risk of becoming psychotic. However, emphysema is uncommon, unlike with cigarette smokers.

Despite its widespread enjoyment, marijuana smoking is banned in many countries, although you would not think so walking along streets in the major cities of western Europe where its characteristic odour pervades the air. It is relatively easy to confirm that an individual has been smoking the drug with established tests for blood, urine, saliva and hair. They detect the principal psychoactive component DELTA9-tetrahydrocannabinol (THC) and its metabolites by immunoassay or mass spectrometric analyses (GC/MS and LC/MS).

In some countries, marijuana is smoked in private rooms tucked away in entertainment buildings. In Taiwan, these are often in karaoke clubs where customers gather to smoke mixed marijuana and tobacco leaves. Although it is a fairly common practice, the police appear to be having some difficulty in catching the smokers red-handed. During raids they are finding that the culprits have fled, leaving an empty room with no physical evidence of marijuana except for the smell in the air.

The word of a policeman in court carries some weight but it is much stronger when backed by forensic data. So the police authorities in Taiwan approached researchers from the Central Police University and the National Tsing Hua University to devise a test for marijuana in indoor air. The team, led by senior reporter Chung-Yen Pai decided to test for THC, since earlier reports confirmed that this compound survives in indoor air.

The first step was to find a reliable sampling device. The researchers rejected several devices that had been used for environmental smoke because they were deemed insufficiently cheap for routine forensic use and too complicated to operate in the field. They settled on a commercial personal air sampler pump and attached an adsorbent tube packed with Tenax-TA. Samples were collected at 100 mL/min over 2 min.

For analysis, the tubes were detached and placed in the desorption chamber of a GC injector and heated to release the trapped volatile compounds. They were analysed by GC/MS with electron ionisation in selected ion monitoring mode, using the GC retention time and three characteristic ions (at m/z 314, 299 and 231) for THC confirmation. The fragment at m/z 231 was used for quantification.

The THC in air from the illegal indoor smoking rooms is usually mixed with tobacco smoke, so the team had to confirm that THC was detectable in this atmosphere. The top 20 compounds found in the smoke of tobacco and marijuana leaves contain 14 common to both plants. Significantly, THC is a small but clearly visible peak in the total ion chromatogram of marijuana smoke that is absent from cigarette smoke. For mixtures of marijuana and tobacco leaves in ratios of 1:1 to 1:15, THC could be detected in the air after all were smoked, except for the most dilute samples.

The amounts of THC varied in marijuana smoke from 15 confiscated plants, ranging from 8.2-1386.7 µg/m3. These variations are probably caused by the fact that the leaves were from different cannabis species.

With detection and quantification limits of 100 and 125 ng/m3, respectively, and a linear calibration range of 0.125-50 µg/m3, the method was applied to air collected from a karaoke bar suspected of marijuana smoking activity. Four smokers had been in a closed, air-conditioned room for about 1.5 h before the police raid but all escaped with their evidence. The air around a couch and table was sampled.

THC was detected in the air at 12.77 µg/m3, which was equivalent to about 300 mg of marijuana leaves being smoked. The strongest peak in the ion chromatogram originated from nicotine, confirming that cigarettes were also smoked.

Positive results like this, that confirm marijuana smoking, can be used to support further action by the police, such as applying for search warrants and arresting suspects. Thereafter, standard testing of biological fluids will establish personal use. With full validation, the method could be used to provide evidence in court.

__________________
SWP



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