Formation of Trifluoroacetylated Ephedrine During the Analysis of a Pseudoephedrine-Formaldehyde Adduct by TFAA Derivatization Followed by GC-MS.
(+)-Pseudoephedrine reacts with formaldehyde to form (4S,5S)-3,4-dimethyl-5-phenyloxazolidine. Gas chromatography-mass spectrometry (GC-MS) analysis after the reaction of this oxazolidine with excess trifluoroacetic acid anhydride (TFAA) shows predominantly N,O-bis(trifluoroacetyl)pseudoephedrine with some of the monotrifluoroacetylated derivative. In addition, variable amounts of N,O-bis(trifluoroacetyl)ephedrine were detected by GC-MS. N,O-bis(trifluoroacetyl)ephedrine was not detected upon trifluoroacetylation of the source (+)-pseudoephedrine, and nuclear magnetic resonance analysis of the (4S,5S)-3,4-dimethyl-5-phenyloxazolidine showed no evidence of the (4R,5S) isomer. This suggests that the N,O-bis(trifluoroacetyl)ephedrine is formed by epimerization during the TFAA derivatization and GC-MS analysis of the pseudoephedrine-formaldehyde adduct.
Lim Bin Abdullah
Ahmad F
AF
Forensic Science Programme, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
Miskelly
Gordon M
GM