山奈酚的电喷雾质谱裂解途径

Fragmentation Pathway of Kaempferol in Electrospray

采用电喷雾质谱技术对山奈酚的质谱过程进行了表征,并用量子化学方法对山奈酚的质谱裂解途径进行了理论研究。依据密度泛函理论,在B3LYP/6-31G(d)水平,对山奈酚的各质谱碎片离子进行了几何结构优化,确定了各碎片的稳定结构;然后,在ROB3LYP/6-311++G(2d,2p)水平计算了形成各碎片离子所需的键断裂能,进而推导出了山奈酚的质谱碎裂途径。计算结果显示,山奈酚主要通过C环碎裂而发生裂解,出现碎片m/z284.7、256.7、228.7、210.7、184.8、168.7和150.7,其中m/z210.7的碎片离子键断裂能最小,m/z150.7的碎片离子键断裂能最大,说明前者很容易由母离子碎片形成,后者较难由母离子碎片形成。

The electrospray ionization （ESI） mass spectrometry was used to study the fragmentation pathway of kaempferol. The fragmentation pathway of kaempferol was also theoretically studied by means of Density Functional Theory （DFT）. The structures of all the fragment ions and the corresponding bond dissociation energies（BDEs） were analyzed by virtue of DFT at ROB3LYP/6-311 ＋＋ G （2d, 2p）/B3LYP/6-31G （d） levels. Based on the comparison with the calculated BDEs, the structure and the origin of each fragment ion were determined, and then the whole fragmentation pathway was deduced. The calculated results show that the fragment ions at m/z 284. 7, 256. 7, 228.7, 210. 7, 184. 8, 168.7 and 150. 7 of kaempferol mainly formed by the cleavage of the C ring. And the BDE of fragment ion at m/z 210.7 is the lowest, while the BDE of fragment ion at m/z 150.7 is the highest, suggesting that the former is evidently easier to form from the parent ion, and the latter is comparatively more difficult to form.