Simultaneous Quantitation of Delta-9-tetrahydrocannabinol (THC) and 11-Nor-9-carboxy-delta-9-tetrahydrocannabinol (THC-COOH) in Serum by GC/MS Using Deuterated Internal Standards and Its Application to a Smoking Study and Forensic Cases

Abstract

A new procedure for the simultaneous detection of delta-9-tetrahydrocannabinol (THC) and its major metabolite, 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (THC-COOH) in serum has been evaluated. The method combines rapid, efficient, solid-phase extraction and simple derivatization by methylation. Analysis and quantitation is performed by gas chromatography/mass spectrometry (GC/MS) using deuterated cannabinoids as internal standards (IS). Reproducibility and sensitivity of the method are good.The procedure is applied to serum specimens collected from a smoking study with 24 volunteers and 212 forensic cases. Results are interpreted based upon the current knowledge about THC metabolism and pharmacokinetics.