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Published:
Journal of Analytical Toxicology,
ISSN 0146-4760,
Volume 30, Issue 4, May 2006,
pp.274-277
Assay of D9-Tetrahydrocannabinol (THC) in Oral Fluid—Evaluation
of the OraSure Oral Specimen Collection Device
Gerold F. Kauert, Stefanie Iwersen-Bergmann, and
Stefan W. Toennes
Institute of Forensic Toxicology, University of Frankfurt, Kennedyallee 104,
D-60596 Frankfurt/Main, Germany
Oral fluid is considered to be an alternative to urine testing
for the detection of acute ingestion of drugs. The OraSure Intercept DOA Oral
Specimen Collection Device (OSCD) has been used in studies for the quantitation
of Δ9-tetrahydrocannabinol (THC), but concerns have been raised. In the
present study, we investigated whether the volume of oral fluid can be determined
and how much THC remains adsorbed on the device. It was found that THC is markedly
adsorbed onto the absorptive pad. The recovery using the standard elution procedure
was only 37.8 ± 9.4% for 10 ng/mL and 55.6 ± 1.0% for 100 ng/mL
of THC in oral fluid (n = 5 each). With an additional methanol wash, a further
25% could be eluted. Therefore, a modification of the procedure was evaluated,
consisting of the addition of 2 mL of methanol to the elution buffer. THC could
be completely recovered over a range of concentrations (1 to 1000 ng/mL). For
the determination of the amount of oral fluid absorbed, a gravimetric approach
was evaluated as the weights of the devices vary only by 0.6% relative standard
deviation. After application of 0.5 mL oral fluid to pads and evaluation of
the weight differences, the applied amount could be estimated with a precision
of 7.5% (n = 8) and an accuracy of 6.1%. From these results it can be concluded
that the OraSure OSCD is useful to collect oral fluid for reliable quantitative
THC assay applying a modified elution procedure and gravimetric determination
of the amount of oral fluid.
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