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| 咖啡酸负离子质谱两低质量碎片离子的解析 |
| The Process and Mechanism of Two Low Mass Fragment Ions In Caffeic Acid Negative Ion Mass Spectrometry |
| 投稿时间：2024-04-08 修订日期：2024-04-25 |
| DOI： |
| 中文关键词: 咖啡酸 质谱裂解 量子化学计算 乙烯基环戊二烯负离子 乙炔基环戊二烯负离子 |
| 英文关键词: caffeic acid mass spectrometry fragmentation quantum chemical calculation vinyl cyclopentadiene anion ethynyl cyclopentadiene anion |
| 基金项目:黑龙江省卫生健康委科研项目(No. 2020-326) |
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| 中文摘要: |
| 通过多级质谱的测定与量子化学计算,解析咖啡酸高分辨负离子模式质谱两个低质量碎片离子m/z 91与m/z 89的生成过程与机理。m/z 91与m/z 89分别为咖啡酸去质子分子(m/z 179)裂解的第三代产物与第四代产物离子,两低质量碎片离子的生成均经过m/z 135的第二代产物离子。咖啡酸去质子分子脱除CO2生成m/z 135后,m/z 135碎片离子经环骈合、环扩张与脱CO2后可生成m/z 91碎片离子；而当m/z 135离子脱H2O时则先生成m/z 117的第三代产物离子,而后m/z 117离子经环收缩脱除CO最终生成m/z 89碎片离子。结合质谱的元素组成,经过渡态、中间产物与碎片离子的结构优化与计算,得到的m/z 91与m/z 89离子的最优结构分别为乙烯基环戊二烯负离子与乙炔基环戊二烯负离子。咖啡酸负离子模式质谱中m/z 91离子强度极弱,其原因来自于m/z 91离子生成途径中的能垒高。 |
| 英文摘要: |
| The formation process and mechanism of two low-mass fragment ions m/z 91 and m/z 89 in caffeic acid high-resolution negative ion mode mass spectrometry were analyzed by multistage mass spectrometry and quantum chemistry calculations. The m/z 91 and m/z 89 were the 3rd and 4th generation product ions of caffeic acid deprotonated molecule (m/z 179), respectively. The two low-mass fragment ions were generated by the 2nd generation product ion of m/z 135. After the deprotonated molecule of caffeic acid removes CO2 to form m/z 135, the m/z 135 fragment ion can form m/z 91 fragment ion after ring parallization, ring expansion and CO2 removal. When the m/z 135 ion removes H2O, it first becomes the 3rd generation product ion of m/z 117, and then the m/z 117 ion removes CO by ring contraction to form the m/z 89 fragment ion. According to the elemental composition of mass spectrometry, the optimal structures of m/z 91 and m/z 89 ions were obtained by optimizing and calculating the structures of transition state, intermediate product and fragment ion. The optimal structures of m/z 91 and m/z 89 ions were vinyl cyclopentadiene anion and ethynyl cyclopentadiene anion, respectively. The m/z 91 ion intensity in the caffeic acid negative ion mode mass spectrometry is extremely weak, which is due to the high energy barrier in the m/z 91 ion formation pathway. |
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