| SOFT - TIAFT 1998 | Scientific Session 3 | Thursday October 8, 1998 |
| DETERMINATION OF CANNABINOIDS IN WATER AND HUMAN SALIVA BY SOLID-PHASE MICROEXTRACTION AND QUADRUPOLE ION TRAP GAS CHROMATOGRAPHY-MASS SPECTROMETRY | |
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Brad J. Hall, Mary Satterfield-Doerr, Aashish R. Parikh, and Jennifer S. Brodbelt The University of Texas at Austin, Department of Chemistry and Biochemistry, Austin, TX 78712-1167, USA |
| Solid-phase microextraction (SPME) was applied to the determination of cannabidiol, D8-tetrahydrocannabinol, (D8-THC), D9-tetrahydrocannabinol (D9-THC), and cannabinol in pure water and human saliva. The inherent extraction behavior of the cannabinoids in pure water was evaluated along with optimization of the method in human saliva. The commercially available polydimethylsiloxane (PDMS) SPME fibers were found to be the best class for the cannabinoid analysis. Partition coefficients were found to be extremely large for all of the cannabinoids (log K > 4.0). Equilibrium times for the 7- and 30 µm PDMS fibers were 50 and 240 minutes, respectively. A shorter extraction time of 10 minutes with the 30 or 100 µm PDMS fiber may be used for multiple extractions from the same vial, thus conserving the sample necessary for analysis and speeding up the total analysis time.
Recoveries for the cannabinoids in saliva, relative to pure water, were dramatically improved by a method developed in our lab involving addition of glacial acetic acid to the sample vial prior to performing SPME. Using this method, recoveries relative to SPME in pure water ranged from 21 - 47 % depending on the cannabinoid. The linear range for spiked saliva samples was established at 5 - 500 ng/mL (r2 > 0.994) with precisions between 11 - 20 % RSD. The ultimate level of detection by SPME for the cannabinoids in saliva was 1.0 ng/mL, with signal-to-noise values > 12. A saliva sample collected 30 minutes after marijuana smoking was subjected to SPME and traditional liquid-liquid extraction analysis. Internal standard quantitation results for D9-THC by both methods yielded comparable results. In conclusion, the SPME method was found to be less laborious and eliminated the use of organic solvents used in traditional methods of extraction. |
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