DETERMINATION OF CANNABINOIDS IN WATER AND HUMAN SALIVA BY SOLID-PHASE MICROEXTRACTION AND QUADRUPOLE ION-TRAP GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

Solid-phase microextraction (SPME) is applied to the determination of cannabidiol, Delta(8)-tetrahydrocannabinol (Delta(8)THC), Delta(9)-tet rahydrocannabinol (Delta(9)-THC), and cannabinol in pure water and hum an saliva. The inherent extraction behavior of the cannabinoids in pur e water is evaluated along with optimization of the method in human sa liva. The commercially available poly(dimethylsiloxane) (PDMS) SPME fi bers were found to be the best class for the cannabinoid analysis. Par tition coefficients were found to be extremely large for all of the ca nnabinoids (log K > 4.0). Equilibrium times for the 7- and 30-mu m PDM S fibers were 50 and 240 min, respectively. A shorter extraction time of 10 min with the 30-mu m PDMS fiber may be used for multiple extract ions from the same vial, thus conserving the sample necessary for anal ysis and speeding up the total analysis time. Recoveries for the canna binoids ire saliva, relative to pure water, were dramatically improved by a method developed in our laboratory involving addition of glacial acetic acid to the sample vial prior to performing SPME. Using this m ethod, recoveries relative to SPME in pure welter ranged from 21 to 47 % depending on the cannabinoid. The linear range for spiked saliva sam ples was established at 5-500 ng/mL (r(2) > 0.994) with precisions bet ween 11 and 20% RSD. The ultimate level of detection by SPME for the c annabinoids in saliva was 1.0 ng/mL, with signal-to-noise values of gr eater than or equal to 12. A saliva sample collected 30 min after mari juana smoking was subject to SPME and traditional liquid-liquid extrac tion analysis, Internal standard quantitation results for Delta(9)-THC by both methods yielded comparable results, indicating that the SPME method of analysis is highly accurate and precise. The level of Delta( 9)-THC by SPME was found to be 9.54 ng/mL for the saliva sample.