EVIDENCE OF TRANSACYLATION OF SCOPOLAMINE IN THE GAS-CHROMATOGRAPH INLET

Scopolamine, a muscarinic receptor antagonist, was derivatized with heptafluorobutyric anhydride (HFBA), separated on a capillary GC column and characterized by electron impact mass spectrometry. The highest ion (m/z 351) in the mass spectrum of HFBA derivatized scopolamine (MW 499) corresponded to the molecular ion of HFB scopoline (M(+), m/z 351). fragmentation pattern in this mass spectrum was different from that obtained for HFB scopoline reported in the literature and used as reference material. In an attempt to explain the differences we suggest that HFB scopolamine undergoes a transacylation in the GC-MS inlet system. This results in an unexpected isomer of HFB scopoline. GC-MS studies of HFB scopolamine, its deuterium-labelled analogues and of HFB atropine support this transacylation hypothesis.