Extraction and Simultaneous Elution and Derivatization of 11-nor-9-Carboxy-Δ9-Tetrahydrocannabinol Using Toxi-Lab SPEC® Prior to GC/MS Analysis of Urine

A new sample preparation procedure is described for the extraction and simultaneous elution and derivation of urine for analysis of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THC-COOH) by gas chromatography/ion trap mass spectrometry (GC/MS). Urine samples are extracted for THC-COOH and d6-THC-COOH internal standard onto a hydrophobic membrane. Extracts are simultaneously eluted and derivatized with MSTFA while on the membrane to produce the corresponding trimethylsilane derivative. Using results of blank urine, the limits of detection and quantitation were 1.1 and 2.5 ng/mL, respectively. The linearity of the assay was 250 ng/mL. The within-run and day-to-day precision ranged 3-5%. Compared with a solid-phase column extraction procedure, the overall time for sample preparation was decreased from 3 h down to 1. The SPEC extraction procedure with trimethyl derivatization produces a cleaner total ion chromatogram than the solid-phase column extraction system (minicolumn) and does not require the use of any organic solvents.