Solid-phase extraction of 11-Nor-Δ9-tetrahydrocannabinol-9-carboxylic acid from urine drug-testing specimens with the Cerex Polycrom-THC(TM) column

Abstract

Confirmation of drugs of abuse by gas chromatography-mass spectrometry (GC-MS) is the most time-consuming process used by drug-testing laboratories. Cost effectiveness and competitive turnaround times for testing results demand fast, efficient, and reliable extraction methods. We applied the Cerex Polycrom-THC solid-phase extraction (SPE) column to the extraction of 11-nor- Δ9-tetrahydrocannabinol carboxylic acid (9-THCA) from urine. This column uses an anion exchange divinyl-benzene copolymer, which requires no pH adjustment after hydrolysis of the THC-glucuronide with base, as is necessary with many other SPE columns. With urine, no preconditioning of the SPE column was necessary. After extraction, trimethylsilyation derivatization was performed with N-methyl-N-(trimethylsilyl) trifluoroacetamide. This further improved efficiency because no heated incubation was required. A method correlation to an existing liquid-liquid extraction was performed. Analysis was on a Finnigan Voyager GC-MS with a 2.5-min run time per injection. Using 9-THCA-d9 deuterated internal standard, the assay was linear from 2 to 2000 ng/mL. Total precision at the 15-ng/mL cutoff concentration was 4.4%. The Cerex column was also evaluated for interference using two common drug-test adulterants, Klear(TM) and Urine Luck(TM). Considerably less interference was observed when compared to an existing liquid-liquid method.