Comprehensive analytical method to identify 11 kinds of synthetic cannabinoids has been investigated by thin layer chromatography (TLC), gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). The analytes used in this study have already been detected from various herbal-type designer drugs: 8 kinds of aminoalkylindoles (AAIs) (JWH-015, JWH-018, JWH-073, JWH-081, JWH-200, JWH-250, JWH-251 and JWH-398), two kinds of cyclohexylphenols (CPs) (CP 47,497 and Cannabicyclohexanol), and a Δ9-tetrahydrocannabinol analog (HU-210).
Although specific color changes were observed for the cannabinoids using Marquis reagent, identification of each analyte based on Rf values was difficult to be obtained by TLC.
On the other hand, GC/MS and LC/MS/MS were appropriate for their qualitative analyses because of their chromatographic and mass spectral differentiation. A semi-polar capillary column DB-5MS showed the best separation and retention properties of the targeted cannabinoids among the tested GC column phases. Also, characteristic fragment ions were observed in each electron ionization-mass spectrum. The observed fragment ions were mainly derived from α-cleavage of ketone and α-cleavage of amine for AAIs, simple cleavage for CPs, and McLafferty rearrangements for HU-210.
Based on the ionization efficiency of the target analytes using LC/MS/MS, electrospray ionization positive mode was selected for AAIs, and negative mode for CPs and HU-210. All analytes were completely separated by gradient elution of ammonium formate aqueous solution-acetonitrile mobile phase on a C18 (ODS) separation column. In addition, characteristic fragment ions were observed in product ion spectra of AAIs and second generation product ion spectra of CPs and HU-210, enabling reliable confirmation.
These results provide useful information not only for simultaneous analyses of the targeted cannabinoids but also for structural assignment of future cannabimimetic compounds that may appear in the illicit drug market.
