Isomerization of cannabidiol and Δ9-tetrahydrocannabinol during positive electrospray ionization. In-source hydrogen/deuterium exchange experiments by flow injection hybrid quadrupole-time-of-flight mass spectrometry.

摘要: RATIONALE Liquid chromatography/tandem mass spectrometry (LC/MS/MS) is frequently used for analysis of cannabinoids in drug abuse control. Despite differences structure, the isomers Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) provide identical fragment spectra after positive electrospray ionization (ESI). For elucidation reason, hydrogen/deuterium (H/D) exchange experiments were performed. METHODS Solutions THC CBD D2O/acetonitrile (50:50, v/v) flow-injected into acetonitrile as mobile phase measured by hybrid quadrupole-time-of-flight (FI-QTOF-MS) targeted MS/MS mode. The MS collision-induced dissociation (CID) at 10, 20 40 eV interpreted with respect to number position exchanged hydrogen atoms. comparison same measurements preformed H2O, addition 0.5% formic acid negative ESI. RESULTS Depending on injected volume response curve, up 7 or 8 atoms deuterium CBD. Positive ESI CID available precursors 4 D-atoms showed that besides OH groups also an H/D carbon non-aromatic part molecules occurred both After ESI, no different substances was found. CONCLUSIONS Injection investigated D2O measurement FI-QTOF-MS proved be efficient way perform experiments. results acid-catalyzed in-source equilibration between leading precursor ions methyl under increased acidic conditions droplets. Therefore, LC/ESI-MS/MS, peak identification abundance ratio multiple reaction monitoring (MRM) transitions not sufficient unambiguous discrimination must supported retention time other experimental evidence. Copyright © 2012 John Wiley & Sons, Ltd.