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-2-p-アミノサリチル酸メチルについて

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The mass spectral fragmentation patterns of methyl p-aminosalicylate were examined with the aid of high-resolution mass spectrometry. The conventional spectrum of this compund is shown in Fig. 1, and several meta-stable ion peaks(Table 1)indicate the presence of two fragmentation pathways(Fig. 2). The accurate masses of each peak were measured by the peakmatching technique with suitably chosen standard substances. i)m/e 167 Ion(Molecular Ion): In order to test the reliability of the present method, the m/e167 peak(Fig. 3)of methyl p-aminosalicylate was compared with the corresponding peak of anthracene(Figs. 4A and 5A)and of stilbene(Figs. 4B and 5B). The observed and the calculated masses of the peak agree satisfactorily. ii)m/e 136 and 135 Ions: The high-resolution spectrum(Fig. 6)reveals that each peak consists of a single fragment ion. By using phenylacetic acid(Fig. 7)as an internal standard, the elemental composition of the peaks was established as follows(Fig. 8): m/e 136, C7H6NO2(M-CH3O), m/e 135, C7H5NO2(M-CH3OH). The fragmentation pathways are depicted in Eqs.1 and 2, respectively. iii)m/e 108 and 107 Ions: From comparisons of the peaks(Fig. 10)to those of phenacetin (Figs. 9 and 11)and of o-xylene(Figs. 12 and 13), the major fragment ions at m/e 108 and 107 were proved to be C6H6NO and C6H5NO, respectively. The fragmentations are not very simple and the formulations(Eqs. 3 and 4)are still tentative. iv)m/e 80 and 79 Ions: The composition of principal ions in Fig. 14 was determined with l-menthol(Fig. 15)as an internal standard. Both peaks were shown to be-13-14m. m. u. lower than the standard peaks(Fig. 16), and this results lead to the composition of C5H6N for m/e 80 and C5H5N for m/e 79 ions(Table II). Formations of these ions are rationalized in Eqs. 5 and 6. v)m/e 53 and 52 Ions: By the similar manner it was found that these ions are hydrocarbon fragments. Naphthalene was selected as a standard. Finally, elemental compositions of major fragment ions of methyl p-aminosalicylate are listed in Table III and the fragmentation pathways are summarized in Fig. 17.

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-2-p-アミノサリチル酸メチルについて

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