Abstract
Differentiation among regioisomers of synthetic cannabinoids in forensic drug analysis is a crucial issue, since all isomers are not regulated by law. New equivalent analogs obtained via minor modification of their preexisting molecules keep on emerging. Isomers formed via substitutional exchange are also a cause for concern. This study is focused on the isomeric molecules that stem from minor modifications of 5F-PB-22. The analytical properties of these molecules and methods of differentiation are reported. Scan mode analysis using gas chromatography–electron ionization-mass spectrometry (GC–EI-MS) was performed using the authentic 5F-PB-22 standard, five regioisomeric quinolinyl ester indoles, and five regioisomeric isoquinolinyl ester indoles. Because it was not possible to separate 5F-PB-22 from the 5-hydroxyquinoline isomer using GC and all analytes showed similar EI mass spectra, liquid chromatography (LC)–tandem mass spectrometry analysis was performed. Using LC, a successful separation of 5F-PB-22 from all isomers could be achieved. Based on the electrospray ionization-mass spectra, the protonated molecular ion at m/z 377.2 was selected as the precursor ion for the regioisomeric and structural isomeric differentiation. Collision-induced dissociation provides relative intensity differences in the product ions among the isomers, enabling mass spectrometric differentiation of the isomers. To our knowledge, this is the first report on mass spectrometric differentiation of 5F-PB-22 and its ten isomers.
Highlights
An increasing number of new psychoactive designer drugs have emerged worldwide during the last decade [1]
All isomers were indistinguishable from 5F-PB-22 by electron ionization (EI)–MS and EI– MS–MS analyses coupled to a GC system, due to their superimposable spectra
While the UV and electrospray ionization (ESI) mass spectra obtained from the liquid chromatography (LC) system were not suitable for structural differentiation due to their close similarity, ESI-MS-MS analysis enabled the differentiation of the isomers by means of differences in relative ion intensity for the product ion at m/z 232, derived from the protonated quasi-molecular ion at m/z 377
Summary
An increasing number of new psychoactive designer drugs have emerged worldwide during the last decade [1]. For effective control of these new psychoactive substances, several legislative approaches have been implemented at the national level. The Ministry of Health, Labour and Welfare of Japan amended the Pharmaceutical Affairs Law in 2006 to implement a new regulatory category, called ‘‘Designated Substances (DSs)’’. The most effective deterrent, a comprehensive regulatory system (generic scheduling) for naphthoylindole-type SCs and synthetic cathinones, was introduced to DSs in 2013. As of April 2016, 2343 compounds are controlled as DSs. The number of vendors on the street and the Internet has been reduced after the repeated expansion of DSs. The number of vendors on the street and the Internet has been reduced after the repeated expansion of DSs On the contrary, such government control of designer SCs may ironically result in the continuing production of new designer drugs and an expansion of structurally related analogs in the clandestine market
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