An Enhanced LC-MS-MS Technique for Distinguishing Δ8- and Δ9-Tetrahydrocannabinol Isomers in Blood and Urine Specimens.

Among the abundance of cannabinoids identified in cannabis, the active parent drug, Δ9-tetrahydrocannabinol (Δ9-THC), and its oxidized metabolite, 11-nor-9-carboxy-Δ9-THC (Δ9-THCCOOH), are attractive analytical targets to detect cannabis use. More recently, confirmation of these analytes may be hindered by a related interfering compound. Forensic toxicology laboratories attribute this phenomenon to an increase in cases containing Δ8-tetrahydrocannabinol (Δ8-THC) and 11-nor-9-carboxy-Δ8-THC (Δ8-THCCOOH).

Phentermine interference and high L-methamphetamine concentration problems in GC-EI-MS SIM Analyses of R-(-)-α-methoxy-α-(trifluoromethyl)phenylacetyl chloride-derivatized amphetamines and methamphetamines†.

In order to achieve chromatographic separation, urine samples shown to be initially positive for amphetamines and methamphetamines in US Department of Defense immunoassays are derivatized with R-(-)-α-methoxy-α-(trifluoromethyl)phenylacetyl chloride (R-(-)-MTPA) prior to gas chromatography-electron impact-mass spectrometry (GC-EI-MS) analysis. Phentermine, a member of the phenethylamine class of drugs and a common appetite suppressant, interferes with GC-EI-MS assays of R-(-)-MTPA-derivatized d-amphetamine, degrading the chromatography of the internal standard and analyte ions and skewing concentration calculations. Additionally, when specimens with high concentrations of l-methamphetamine are derivatized with R-(-)-MTPA, signal peaks have the potential to be misidentified by integration software as d-methamphetamine.