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Screening method for 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in urine using hollow fiber membrane solvent microextraction with in-tube derivatization.

Journal of chromatography. B, Biomedical sciences and applications (2001-08-28)
K E Kramer, A R Andrews
ABSTRACT

An efficient and inexpensive screening technique for the simultaneous clean-up, extraction, and derivatization of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) from urine has been developed. Using the principles of solvent microextraction in the form of a 20-microl volume of solvent placed inside a permeable hydrophobic polypropylene hollow fiber membrane, the analyte of interest is preconcentrated inside this tubing as the bulk sample solution is stirred for a given extraction time. The pH of the sample is raised by adding buffer after which the charged moiety is extracted as an ion pair with tetramethylammonium hydrogen sulfate. Using a mixture of N,O-bis(trimethylsilyl)trifluoroacetamide and octane as the extraction solvent allows the GC-unstable carboxylic acid metabolite to be derivatized during the extraction without prior sample clean-up steps such as filtration of the urine. After an 8-min extraction, a 6-microl portion is drawn up with a syringe and directly injected into a gas chromatograph for separation and analysis. Samples as low as 10 ng ml(-1) were analyzed successfully and the limit of detection was estimated at 1.0 ng ml(-1) with relative standard deviations lower than 10% in the final protocol.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Octane, anhydrous, ≥99%
Sigma-Aldrich
Octane, reagent grade, 98%
Supelco
Octane, analytical standard
Sigma-Aldrich
Octane, puriss. p.a., ≥99.0% (GC)
Sigma-Aldrich
Octane, electronic grade, ≥99.999% metals basis, ≥99% (CP)

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