高分解能質量スペクトルによるフラグメンテーションの解析IIIバルビタールについて

抄録

The mass spectral fragmentation patterns of barbital (diethylbarbituric acid) were studied by using the high-resolution mass spectrometry. As is shown in Fig. 1, barbital exhibits several characteristic peaks correlated each other by the existence of meta-stable ion peaks (Fig. 2) .
The accurate masses of apeak at m/e156 were determined by the peak-matching technique with an M+2 peak of diphenyl as a standard (TableI) . Peaks at m/e 155, 141, 112, and 83 were examined in the similar manner with suitably chosen standard substances, and the results were summarized in Table II.
Elemental compositions of the main fragment ions of peaks at m/e 98, 70, 69, 55, 44, and 41 were assigned from comparison of allowed atomic combinations with the number of observed peaks (Fig. 3-8, Table III-VIII). Fragment ions and fragmentation sequences of barbital were represented in Fig. 9.
Plausible mechanistic formulations of each fragmentation step were depicted in Eq. 1, 2, 3, 4, and 5, respectively. It was noted that the interconversion of keto-and enol-forms of M-28 ion(m/e156)(Eq. 6)was not possible in a mass spectrometer.