Characterization of the designer drug bk-2C-B (2-amino-1-(bromo-dimethoxyphenyl)ethan-1-one) by gas chromatography/mass spectrometry without and with derivatization with 2,2,2-trichloroethyl chloroformate, liquid chromatography/high-resolution mass spectrometry, and nuclear magnetic resonance

Rationale: We describe the analytical characterization of the designer drug bk-2C-B, a cathinone derivative, contained in a seized tablet, in the absence of an analytical standard.

Methods: The analytical techniques employed include gas chromatography/mass spectrometry (GC/MS), without and with derivatization with 2,2,2-trichloroethyl chloroformate, liquid chromatography/high-resolution-MS (LC/HRMS) with an Orbitrap® analyzer, and nuclear magnetic resonance (NMR). LC/HRMS measurements consisted of accurate mass measurements of MH(+) ionic species under full scan conditions; comparison of experimental and calculated MH(+) isotopic patterns; examination of the isotopic fine structure (IFS) of the M+1, M+2, M+3 isotopic peaks relative to the monoisotopic M+0 peak; study of MH(+) collision-induced dissociation (CID) product ions obtained in fragmentation experiments.

Results: GC/MS analysis gave highly informative EI mass spectra, particularly after the derivatization of bk-2C-B with 2,2,2-trichloroethyl chloroformate. The application of LC/HRMS, allowing for accurate mass measurements at 100,000 resolving power, greatly enhanced analytical capabilities in structural characterization of this new designer drug. HRMS allowed us to obtain the accurate mass measurements of bk-2C-B MH(+) ionic species, with a mass accuracy of 2.19 ppm; fully superimposable experimental and calculated MH(+) isotopic patterns, with RIA1 and RIA2 values <4%; the IFS of the M+1, M+2, M+3 isotopic peaks relative to the monoisotopic M+0 peak completely in accordance with theoretical values. These findings enabled us to obtain the elemental composition formula of the seized drug. Furthermore, characteristic MH(+) CID product ions enabled the characterization of the bk-2C-B molecular structure. The presence of (79)Br and (81)Br isotopes in the substance molecule produced a characteristic isotopic pattern in most MS spectra. Lastly, NMR spectra allowed us to obtain useful information about the position of substituents in the designer drug.

Conclusions: The combination of all the analytical techniques employed allowed the characterization of the seized psychoactive substance, in spite of the lack of a reference standard.