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.
- Aspartame decomposition
- Tshermospray LC/MS