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Published:
Journal of Analytical Toxicology,
ISSN 0146-4760,
Volume 24,
Number 6, September 2000, pp. 433-437
Here is where the title stuff goes
Automated
Extraction of 11-nor-Æ9-Tetrahydrocannabinol Carboxylic Acid from Urine Samples
Using the ASPEC XL™ Solid-Phase Extraction System*
Marinus C.J. Langen, Gertjan A. de Bijl, and Antoine
C.G. Egberts
Dutch Laboratory for Drugs and Doping, Laboratory Hospital Pharmacy Midden-Brabant,
P.O. Box 90107, 5000 LA Tilburg, The Netherlands
The analysis of 11-nor-Æ9-tetrahydrocannabinol-carboxylic
acid (THCCOOH, the major metabolite of cannabis) in urine with gas chromatography
and mass spectrometry (GC–MS) and solid-phase extraction (SPE) sample preparation
is well documented. Automated SPE sample preparation of THCCOOH in urine, although
potentially advantageous, is to our knowledge poorly investigated. The objective
of the present study was to develop and validate an automated SPE sample-preparation
step using ASPEC XL suited for GC–MS confirmation analysis of THCCOOH in
urine drug control. The recoveries showed that it was not possible to transfer
the protocol for the manual SPE procedure with the vacuum manifold to the ASPEC
XL without loss of recovery. Making the sample more lipophilic by adding 1 mL
2-propanol after hydrolysis to the urine sample in order to overcome the problem
of surface adsorption of THCCOOH led to an extraction efficiency (77%) comparable
to that reached with the vacuum manifold (84%). The reproducibility of the automated
SPE procedure was better (coefficient of variation 5%) than that of the manual
procedure (coefficient of variation 12%). The limit of detection was 1 ng/mL,
and the limit of quantitation was 4 ng/mL. Precision at the 12.5-ng/mL level
was as follows: mean, 12.4 and coefficient of variation, 3.0%. Potential carryover
was evaluated, but a carryover effect could not be detected. It was concluded
that the proposed method is suited for GC–MS confirmation urinalysis of
THCCOOH for prisons and detoxification centers. Reproduction
of editorial content of this journal is prohibited without publisher’s
permission.
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