Simultaneous analysis of Δ⁹-THC and its major metabolites in urine, plasma, and meconium by GC-MS using an immunoaffinity extraction procedure

A simple extraction procedure for Δ9-tetrahydrocannabinol (Δ9-THC) and its metabolites from various biological specimens was developed based on immunoaffinity chromatography. Using the affinity resin prepared by immobilization of THC antibody onto cyanogen bromide-activated Sepharose 4B, Δ9-THC and its major metabolites including 11-nor-Δ9-THC-9-carboxylic acid (Δ9-THCCOOH), 11-hydroxy-Δ9-THC (11-OH-Δ9-THC), and 8β, 11-dihydroxy-Δ9-THC (8β, 11-diOH-Δ9-THC) were extracted simultaneously from plasma or urine after enzyme hydrolysis. The samples were derivatized as TMS derivatives and analyzed by gas chromatography-mass spectrometry in EI mode with SIM monitoring. Greater than 87% extraction recovery of the four analytes was obtained from both plasma and urine at 5 and 50 ng/mL concentration levels. The method was also used for meconium analysis with some modification. The extraction recovery from meconium, however, was lower than that of plasma and urine, ranging from 52 to 72% at the 10-ng/g level. All compounds showed good linearity within the tested ranges up to 100 ng/mL (g). The limits of detection ranged from 0.5 to 2.5 ng/mL in plasma and urine, and from 1.0 to 2.5 ng/g in meconium. Analysis of 24 meconium specimens showed that 11-OH-Δ9-THC is indeed an important metabolite in meconium.