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Published:
Journal of Analytical Toxicology,
ISSN 0146-4760,
Volume 26, Number 8, November/December,
pp. 554-560
Fully Automated Determination of Cannabinoids in Hair Samples
using Headspace Solid-Phase Microextraction and Gas Chromatography–Mass
Spectrometry
Frank Musshoff*, Heike P. Junker, Dirk W. Lachenmeier,
Lars Kroener, and Burkhard Madea
Institute of Legal Medicine, University of Bonn, Stiftsplatz 12, D-53111 Bonn,
Germany
This paper describes a fully automated procedure using alkaline
hydrolysis and headspace solid-phase microextraction (HS-SPME) followed by on-fiber
derivatization and gas chromatographic–mass spectrometric (GC–MS)
detection of cannabinoids in human hair samples. Ten milligrams of hair was
washed with deionized water, petroleum ether, and dichloromethane. After the
addition of deuterated internal standards the sample was hydrolyzed with sodium
hydroxide and directly submitted to HS-SPME. After absorption of analytes for
an on-fiber derivatization procedure the fiber was directly placed into the
headspace of a second vial containing N-methyl-N-trimethylsilyl-trifluoroacetamide
(MSTFA) before GC–MS analysis. The limit f detection was 0.05 ng/mg for
D9-tetrahydrocannabinol (THC), 0.08 ng/mg for cannabidiol (CBD), and 0.14 ng/mg
for cannabinol (CBN). Absolute recoveries were in the range between 0.3 and
7.5%. Linearity was proved over a range from 0.1 to 20 ng/mg with coefficients
of correlation from 0.998 to 0.999. Validation of the whole procedure revealed
excellent results. In comparison with conventional methods of hair analysis
this automated HS-SPME-GC–MS procedure is substantially faster. It is
easy to perform without use of solvents and with minimal sample quantities,
but with the same degree of sensitivity and reproducibility. The applicability
was demonstrated by the analysis of 25 hair samples from several forensic cases.
The following concentration ranges were determined: THC 0.29–2.20 (mean
1.7) ng/mg, CBN 0.55–4.54 (mean 1.2) ng/mg, and CBD 0.53–18.36 (mean
1.3) ng/mg. 11-nor-D9-Tetrahydrocannabinol-9-carboxylic
acid could not be detected with this method.
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