Differentiation of AB-FUBINACA and its five positional isomers using liquid chromatography-electrospray ionization-linear ion trap mass spectrometry and triple quadrupole mass spectrometry.

PURPOSE

Positional isomer differentiation is crucial for forensic analysis. The aim of this study was to differentiate AB-FUBINACA positional isomers using liquid chromatography (LC)-electrospray ionization (ESI)-linear ion trap mass spectrometry (LIT-MS) and LC-ESI-triple quadrupole mass spectrometry (QqQ-MS).

METHODS

AB-FUBINACA, its two fluorine positional isomers on the phenyl ring, and three methyl positional isomers in the carboxamide side chain were analyzed by LC-ESI-LIT-MS and LC-ESI-QqQ-MS.

RESULTS

Four of the positional isomers, excluding AB-FUBINACA and its 3-fluorobenzyl isomer, were chromatographically separated on an ODS column in isocratic mode. ESI-LIT-MS could discriminate only three isomers, i.e., the 2-fluorobenzyl isomer, the -(1-amino-2-methyl-1-oxobutan-2-yl) isomer, and the -(1-amino-1-oxobutan-2-yl)--methyl isomer, based on their characteristic product ions observed at the MS stage in negative mode. ESI-QqQ-MS differentiated all six isomers in terms of the relative abundances of the product ions that contained the isomeric moieties involved in collision-induced dissociation reactions. The six isomers were more clearly and significantly differentiated upon comparison of the logarithmic values of the product ion abundance ratios as a function of collision energy.

CONCLUSIONS

The present LC-MS methodologies were useful for the differentiation of a series of AB-FUBINACA positional isomers.