Separation of isomers of new psychoactive substances and isotope-labeled amphetamines using UHPSFC-MS/MS and UHPLC-MS/MS

ABSTRACT

The use of sub-2 µm particles columns is finding its use in ultrahigh-pressure supercritical fluid chromatography (UHPSFC), opening up for fast analysis and high-resolution separations. The development of new and more robust systems also makes the technique more interesting for bioanalytical analysis, where the need for reproducible and fast analysis with little downtime is great. One area where the use of UHPSFC could become a useful tool is in the separation of structural isomers of new psychoactive substances (NPS). 2-, 3-, and 4- structural isomers of fluoroamphetamine, fluoromethamphetamine, and methylmethcathinone, isomeric pairs of the synthetic cannabinoids UR-144/UR-144 degradant, XLR-11/XLR-11 degradant, JWH-015/JWH-073, and JWH-019/JWH-122, as well as amphetamine and several stable isotope-labeled amphetamine internal standards were separated with UHPSFC-MS/MS and compared with ultrahigh-pressure liquid chromatography (UHPLC) MS/MS. NPS isomers that were difficult to separate with reversed-phase UHPLC-MS/MS were separated by UHPSFC; in most cases with an orthogonal retention order to UHPLC. In contrast to the behavior seen when using reversed-phase UHPLC, the deuterated amphetamines eluted later than amphetamine with UHPSFC. ¹³C₆-labeled amphetamine coeluted with amphetamine for all conditions, making this the best choice of an internal standard.

GRAPHICAL ABSTRACT

KEYWORDS:

• Isomer separation
• isotope-labeled internal standards
• new psychoactive substances
• supercritical fluid chromatography
• synthetic cannabinoids

Acknowledgments

The authors would like to thank Anja Valen for the preparation of the molecular structures in Figure 1 and Ingvar Betnér for advice regarding the separation of JWH-019 and JWH-122. Guy Wilson and Ingvar Betnér are acknowledged for their valuable comments and for critical reading of the manuscript.