有机光谱化学分析 (4).pdf

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1、P2:Hello everyone,welcome to todays class-Organic Spectroscopic Analysis.In this lecture,lets learn a new mass spectrometry technology.（大家好，欢迎学习今天的课程有机波谱分析。在本次课中，让我们学习一种新的质谱技术。）P3:Mass spectrometry uses an instrument called mass spectrometer.Five components of the mass spectrometer are sample inlet,

2、ion source,mass analyzer,detector and recorder.（质谱法使用一种称为质谱仪的仪器。质谱仪的五个组成部分分别是进样系统，离子源，质量分析器，检测器和记录仪。）In inlet system,the method of sample introduction to the ionisation source often depends on the ionisation method being used,as well as the type and complexity of the sample.（在进样系统中，将样品引入电离源的方法通常取决于所

3、使用的电离方法，以及样品的类型和复杂性。）Samples can be introduced to the mass spectrometer directly via solids probe,or in the case of mixtures,by the intermediary of chromatography device.（样品可以通过固体探针直接引入质谱仪，或者在混合物的情况下，通过色谱仪导入。）Ion source is the place to ionize samples into charged ions.Mass analyzer is able to separa

4、te ions according to their mass(m)-to-charge(z)ratios(m/z).Detector is used to detect the produced ions in MS.Recorder is used to record a mass spectrum.（离子源是将样品电离为带电荷离子的地方。质量分析器能够根据离子的质量（m）与电荷（z）之比（m/z）对其进行分离。检测器用于检测 MS 中产生的离子。记录仪用于记录质谱。）P4:How does a mass spectrometer work?（此处插入动画 lcms-tof）Lets se

5、e the picture here.Firstly,the sample has been introduced into the ionisation source of the instrument.Once inside the ionisation source,the sample molecules are ionised.（质谱仪如何工作？（此处插入动画 lcms-tof）让我们看看这张图片。首先，必须样品进入到质谱仪的电离源中。一旦进入电离源，样品分子便被电离。）Secondly,these ions are extracted into the analyser regio

6、n of the mass spectrometer where they are separated according to their mass(m)-to-charge(z)ratios(m/z).（其次，这些离子被提取到质谱仪的质量分析器区域中，在此处根据它们的质量（m）与电荷（z）之比（m/z）进行分离。）Finally,the separated ions are detected and this signal sent to a data system where the m/z ratios are stored together with their relative a

7、bundance for presentation in the format of a m/z spectrum.（最终，检测到分离的离子，并将此信号发送到数据系统，在该系统中，m/z 比值及其相对丰度一起存储，以 m/z 谱图的形式表示。）The analyser and detector of the mass spectrometer,and often the ionisation source too,are maintained under high vacuum to give the ions a reasonable chance of travelling from on

8、e end of the instrument to the other without any hindrance from air molecules.（质谱仪的分析仪和检测器以及通常的电离源也都保持在高真空下，以使离子有合理的机会从仪器的一端传播到另一端，而不会受到空气分子的任何阻碍。）P5:For example,the acetone molecule is introduced in the sample inlet.It is heated as vapor and ionized in the ion source to produce an molecular ion,by

9、removing an electron from the neutral molecule according to its ionization energy.（例如，将丙酮分子引入进样系统，通过根据中性分子的电离能将一个电子从中性分子中去掉，并加热为蒸气，及在离子源中离子化以产生分子离子。）The excess internal energy of the molecular ion makes it dissociate into fragment ions,such as ions with m/z of 15,27,29,43 and 57.All the produced fra

10、gment ions and molecular ions fly into the following mass analyzer to be separated according to their m/z ratios,then arrive at the detector and are recorded as a mass spectrum.（分子离子过多的内能使其分解为碎片离子，例如 m/z 为 15、27、29、43 和 57 的离子。所有产生的碎片离子和分子离子飞到随后的质量分析器中根据它们的 m/z 进行分离，然后到达检测器并被记录为质谱图。）P6:x-axis is the

11、 m/z,from the left to the right becomes bigger.y-axis is the relative intensity.Higher RI means more ions at certain m/z.The RI of the base peak is 100%.All other peak intensities are expressed as the percentage of their peak area corresponding to the intensity of the base peak.（x 轴为 m/z 比值，从左到右变大。y

12、 轴对应相对强度（RI）。较高的 RI 意味着特定的 m/z 有更多的离子。基峰的 RI 为 100。其他峰强度均表示为其峰面积与基峰峰面积的相对百分比。）P7:Molecular ion is singly charged intact molecules.Base peak is the peak with the highest intensity.Fragment ions are produced by the dissociation of molecular ions.（分子离子是单电荷的完整分子。基峰是强度最高的峰。碎片离子是通过分子离子的解离产生的。）(插入图 8)Signa

13、l generated at the detector is dependent on upon number of ions of any particular mass arriving at the analyzer.Most intense peaks will arise from stable ions and from cleavages that occur most readily.在检测器处产生的信号取决于到达分析器的任何特定质量的离子数。最强的峰将来自稳定的离子和最容易发生的裂解反应。P9:There are many different ionization sourc

14、es according to different ionization principles,such as electron impact，(EI）,Chemical Ionization，(CI）,Field Desorption(FD),Fast Atom Bombardment(FAB),Electrospray Ionization(ESI),Laser Desorption(LD)and Matrix Assisted Laser Desorption/Ionization(MALDI).P9：根据不同的电离原理，有许多不同类型的电离源，例如电子轰击电离，（EI），化学电离，（C

15、I），场解吸（FD），快速原子轰击（FAB），电喷雾电离（ESI），激光解吸（LD）和基质辅助激光解吸/电离（MALDI）。P10:EI ionization method is suitable for non thermolabile compounds.The volatility of the sample is required.Sample molecules in vapor state are bombarded by fast moving electrons,conventionally 70 eV energy.（EI 电离方法适用于非热不稳定化合物。需要样品有挥发性。蒸

16、汽状态下的样品分子会受到快速移动的电子轰击，通常电子束的能量为70 eV，这导致离子的形成。）(插入图 11)This results in ion formation.One electron from the highest orbital energy is removed,and as a consequence molecular ions are formed.Some of this molecular ions decompose and fragment ions are formed.来自能量最高轨道的一个电子被去除，结果形成了分子离子。该一部分分子离子裂解形成碎片离子。T

17、he fragmentation of a given ion is due to the excess of energy that it requires within the ionization.Fragment ions can be odd electron or even electron.特定离子的分裂是由于电离过程中获得过多能量所致。碎片离子可以是奇电子或偶电子。Molecular ions formed in electron impact ionization are odd electron ions.Odd electron fragment ions are for

18、med by direct cleavage(e.g.direct cleavage of a C-C bond).Even electron fragment ions are often formed by rearrangement(e.g.proton transfer).电子轰击电离源中形成的分子离子是奇数电子离子。通过直接裂解（例如，C-C 键的直接裂解）形成奇数电子碎片离子。碎片离子也经常通过重排形成（例如质子转移）。P13:In CI,ion molecule reactions occur between ionized reagent gas molecules G and

19、 volatile analyte neutral molecules(M)to produce analyte ions.Pseudo-molecular ion MH+(positive ion mode)or M-H-(negative ion mode)are often observed.在 CI 中，离子化的反应气体分子 G 和挥发性分析物中性分子（M）之间发生分子离子反应，从而产生分析物离子。经常观察到准分子离子 MH+（正离子模式）或M-H-（负离子模式）。Unlike molecular ions obtained in EI method,MH+and M-H-detect

20、ion occurs in high yield and less fragment ions are observed.The main reagent gases used in CI are:Ammonia,Methane,and Isobutane.Choice of reagent gas affect the extend of fragmentation of the quasi-molecular ion.与 EI 方法获得的分子离子不同，MH+和M-H-检测的产率很高，观察到的碎片离子较少。CI 中主要使用的反应气体为：氨，甲烷和异丁烷。反应气体的选择会影响准分子离子裂解的范

21、围。For organic chemists,Chemical Ionization(CI)is especially useful technique when no molecular ion is observed in EI mass spectrum,and also in the case of confirming the mass to charge ratio of the molecular ion.对于有机化学家来说，当在 EI 质谱图中未观察到分子离子时，以及在确认分子离子的质荷比的情况下，化学电离（CI）是特别有用的技术。Chemical ionization tec

22、hnique uses virtually the same ion source device as in electron impact,except,CI uses tight ion source,and reagent gas.（插入图片 14）Reagent gas(e.g.ammonia)is first subjected to electron impact.【化学电离技术所使用的离子源装置与电子撞击几乎是一样的，除了CI 使用的是紧密的离子源和试剂气体。（插入图片 14）试剂气体(如氨)首先受到电子冲击。】Sample ions are formed by the inte

23、raction of reagent gas ions and sample molecules.This phenomenon is called ion-molecule reactions.Reagent gas molecules are present in the ratio of about 100:1 with respect to sample molecules.【样品离子是由试剂气体离子和样品分子相互作用而形成的。这种现象被称为离子-分子反应。试剂气体分子与样品分子的比例约为100:1。】Positive ions and negative ions are formed

24、 in the CI process.Depending on the setup of the instrument,such as source voltages,detector,etc.only positive ions or only negative ions are recorded.【正离子和负离子在 CI 过程中形成。根据仪器的设置，如源电压、检测器等，只有正离子或负离子被记录。】P15:Proton transfer is one of the simple processes observed in positive CI:One of the decisive par

25、ameter in this reaction is the proton affinity.For the reaction to occur,the proton affinity of the molecule M must be higher that the one of the gas molecule.The main reagent gases used in CI are:Ammonia,Methane,and Isobutane.Choice of reagent gas affect the extend of fragmentation of the quasi-mol

26、ecular ion.【质子转移是 CI 中简单的正电离过程之一：该反应中的决定性参数之一是质子亲和力。为了发生反应，分子 M的质子亲和力必须高于气体分子的质子亲和力。CI 中使用的主要反应气为：氨，甲烷和异丁烷。反应气的选择会影响准分子离子裂解的范围。】So todays class,we have talk about the instrument-mass spectrometry.Well continue to study different ion sources in the next class.Thank you for watching.今天这节课我们讲了质谱仪，在下一节课中，我们会继续学习不同的离子源。谢谢收看！