Determination of Δ9-tetrahydrocannabinol in indoor air as an indicator of marijuana cigarette smoking using adsorbent sampling and in-injector thermal desorption gas chromatography-mass spectrometry

The marijuana leaves are usually mixed with tobaccos and smoked at amusement places in Taiwan. Recently, for investigation-legal purposes, the police asked if we can identify the marijuana smoke in a KTV stateroom (a private room at the entertainment spot for singing, smoking, alcohol drinking, etc.) without marijuana residues. A personal air-sampler pump fitted with the GC liner-tube packed with Tenax-TA adsorbent was used for air sampling. The GC-adsorbent tube was placed in the GC injector port and desorbed directly, followed by GC-MS analysis for the determination of Delta(9)-tetrahydrocannabinol (Delta(9)-THC) in indoor air. The average desorption efficiency and limit of detection for Delta(9)-THC were 89% and 0.1 mu g m(-3), respectively, approximately needing 1.09 mg of marijuana leaves smoked in an unventilated closed room (3.0 m x 2.4 m x 2.7 m) to reach this level. The mean Delta(9)-THC contained in the 15 marijuana plants seized from diverse locations was measured to be 0.32%. The Delta(9)-THC in room air can be successfully identified from mock marijuana cigarettes, mixtures of marijuana and tobacco, and an actual case. The characteristic Delta(9)-THC peak in chromatogram can serve as the indicator of marijuana. Positive result suggests marijuana smoking at the specific scene in the recent past, facilitating the formulation of further investigation. (C) 2007 Elsevier B.V. All rights reserved.