Complementary methods based on three mass spectrometric ionization techniques arepresented for the determination of the thermal decomposition products of the α-dipeptide sweetener aspartame. Thermal decomposition products generated in acidic aqueous model systems were separated by ion-pair high-performance liquid chromatography and either (1) isolated and concentrated on solid-phase extraction columns for determination by direct insertion probe/electron impact mass spectrometry; (2) determined by gas chromatography/mass spectrometry as N-trifluoroethyl-O-trimethylsilyl polyamino alcohol derivatives; or (3) determined directly via Thermospray liquid chromatography/mass spectrometry. These procedures resulted in the elucidation and structural determination of four compounds: (1) β-aspartame, a non-sweet constitutional isomer of aspartame; (2) its anhydro analogue, methyl-3-phenyl-2-(3-amino-2,5-dioxo-1-pyrrolidinyl propanoate; (3) the non-sweet β-L-aspartyl-L-phenylalanine; and (4) its anhydro analogue, 3-phenyl-2-(3- amino-2,5-dioxo-1-pyrrolidinyl)propanoic acid.
Bibliographical noteFunding Information:
The authors thank Larry D. Bowers and Maurice M. Kreevoy for many stimulating and helpful discussions during the preparation of this manuscript. The technical assistance of Daniel A. Garteiz, Thomas P. Krick and David W.Baloga is also greatly appreciated. This paper is scientific journal series No. 15381 from the University of Minnesota Agric. Exp. station. This project wassupported inpartby the University of Minnesota Agric. Exp. Station Grant No. 18-78 and byNational Science Foundation grant CBT-8512914.
- Aspartame decomposition
- Tshermospray LC/MS