2,5-Diaziridinyl-3,6-bis(carboethoxyamino)-1,4-benzoquinone II: Isolation and characterization of degradation products.

A direct high-performance liquid chromatographic (HPLC) method was applied to monitor 2,5-diaziridinyl-3,6-bis(carboethoxyamino)-1,4-benzoquinone (I) and its degradation products in pharmaceutical vehicles at 25 +/- 0.1 degrees. At the optimal pH for stability of I, an increase in buffer concentration [phosphate and tris(hydroxymethyl)-aminomethane] or ionic strength accelerated degradation. The reaction rate in the solutions studied followed pseudo-first-order kinetics. Degradation products were characterized by mass spectrometry after isolation by semipreparative HPLC. Different degradation pathways prevailed in acidic and basic media. The acid-catalyzed reaction resulted in consecutive aziridine ring opening, while the base-catalyzed reaction led to nucleophilic displacement of thie aziridine ring(s).