Abstract
A new proton magnetic resonance (PMR) method for the quantitative determination of 2,5-Diaziridinyl-3,6-bis (carboethoxyamino)-1,4-benzoquinone and its acid decomposition products in dimethylsulfoxide-d6, and at 35 ± l° is described. The PMR spectrum of 2,5-Diaziridinyl-3,6-bis (carboethoxyamino) -1,4-benzoquinone shows singlet system at Δ 2.2 due to the protons of the two aziridine rings. The integral ratio of this signal to that of the methyl protons signal at Δ 1.2 and the methalene protons signal at Δ 4.05 is 4:3:2 in the intact molecule. The acid catalayzed decomposition results in disturbance of this ratio since the two aziridine rings are opened consecutively and a new multiplet signal appear at Δ 3.4–3.7 due to the ethelene group protons of the hydroxyethylamino group formed upon decomposition of aziridine moiety. Comparing the integral of the signal at Δ 1.2, 2.2, 3.4–3.7 and 4.03 to that of the sharp singlet at Δ 6.83 of 1,4 p-benzoquinone which is used as internal standard constitute the basis of the method.
The proposed method is in addition of being simple and rapid it offers accuracy and reproducibility when applied for the determination of the pure crystalline compound. An average recovery percent of 100.41 ± 0.1 was obtained. While in acid catalyzed decomposed samples reasonably accurate results are obtained, the method is inapplicable for base-catalyzed decomposed samples due to the rapid conversion of benzoquinone to hydroquinone which results in inaccuracies in the determinations.
The method is based on the PMR spectrum that could be used to assure the identity and purity of the drug compound.