Identification and imaging of indole-3-carboxamide cannabinoids in hair using matrix-assisted laser-desorption/ionization mass spectrometry

Abstract

Different kinds of new synthetic cannabinoids (SCs) have been continuously developed to evade drug monitoring. Segmental hair analysis offers a longer period for retrospective drug detection compared with blood or urine. In this study, matrix-assisted laser-desorption/ionization-Fourier transform ion cyclotron resonance mass spectrometric imaging (MALDI-FT ICR MSI) was developed for direct identification and imaging of synthetic indole-3-carboxamide cannabinoids in hair samples using the positive ion mode. The target SCs include N-(adamantan-1-yl)-1-pentyl-1H-indole-3-carboxamide (APICA), N-(1-amino-3-methyl-1-oxobutan-2-yl)-1-(5-fluoropentyl)-1H-indole-3-carboxamide (5F-AB-PICA), N-(1-amino-3,3-dimethyl-1-oxobutan-2-yl)-1-pentyl-1H-indazole-3-carboxamide (ADB-PINACA) and N-(1-amino -3,3-dimethyl-1-oxobutan-2-yl)-1-(5-fluoropentyl)-1H-indole-3-carboxamide (5F-ADBICA). The MALDI-MS and MS/MS were first performed on the scraped hair soaked in a mixture of the four SCs after matrix sublimation. This method may provide a detection power for SCs to the 0.1 ng level per 2 cm hair. Target cannabinoids were identified by MS1 and MS2. Matrix deposition methods including airbrush sprayer and sublimation were compared. The method was then applied in revealing the spatial distribution of APICA and 5F-ADBICA in real hair samples from two drug abusers by comparing MS1 and MS2 spectra. The metabolites of APICA and 5F-ADBICA were also presumed to be present in the positive hair samples. Furthermore, a comprehensive comparison between a MALDI-FT ICR MS and a MALDI time-of-flight–MS instrument was performed in detection-sensitivity and specificity for positive real samples. The proposed method provides a powerful tool for drug supervision and forensic medicine analysis in a wide time window, and the sample amount required was also decreased.