📚 Mass Spectrometry | 质谱法
Mass spectrometry is a powerful analytical technique used to determine the relative atomic mass, relative molecular mass, and structural features of chemical substances. In A-Level Chemistry, it appears both in physical chemistry for relative atomic mass calculations and in organic chemistry for identifying unknown compounds from fragmentation patterns.
质谱法是一种强大的分析技术，用于测定化学物质的相对原子质量、相对分子质量以及结构特征。在 A-Level 化学中，它既出现在物理化学中用于相对原子质量的计算，也出现在有机化学中用于根据碎裂模式鉴定未知化合物。
1. The Basic Principle | 基本原理
A mass spectrometer measures the mass-to-charge ratio (m/z) of ions produced from a sample. The sample is first vaporised if necessary, then ionised, and the resulting positive ions are separated according to their m/z values before reaching a detector.
质谱仪测量由样品产生的离子的质荷比 (m/z)。样品首先在必要时被汽化，然后被离子化，产生的正离子根据其 m/z 值进行分离，最后到达检测器。
Because only charged particles are deflected or accelerated, neutral molecules must be converted into ions. The output is a mass spectrum in which peak height represents relative abundance and the horizontal axis represents m/z.
由于只有带电粒子才会被偏转或加速，中性分子必须转化为离子。输出的质谱图中，峰高代表相对丰度，横轴代表 m/z。
2. Ionisation Methods | 离子化方法
Cambridge A-Level specifications focus on two ionisation techniques: electron impact (also called electron ionisation) and electrospray ionisation. The choice depends on the volatility and thermal stability of the sample.
剑桥 A-Level 大纲重点考察两种离子化技术：电子轰击（也称为电子电离）和电喷雾离子化。选择哪种方法取决于样品的挥发性和热稳定性。
Electron impact is used for small, volatile organic molecules, while electrospray is preferred for larger, thermally fragile molecules such as proteins
Published by TutorHao | A-Level Chemistry Revision Series | aleveler.com
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