紫外光谱分析演讲分析实用教案

1、会计学1紫外光谱分析紫外光谱分析(un p fn x)演讲分析演讲分析第一页，共49页。UV radiation is the electromagnetic radiation of a wavelength shorter than that of visible light, but longer than that of x-rays. The typical range of UV wavelength is 10-400 nm.第1页/共49页第二页，共49页。第2页/共49页第三页，共49页。第3页/共49页第四页，共49页。第4页/共49页第五页，共49页。第5页/共49页第六

2、页，共49页。, -律。第6页/共49页第七页，共49页。吸光系数。n A= lC=-lgI/I0; 即=A/lCnI0: 入射光强度；I: 透射光强度第7页/共49页第八页，共49页。第8页/共49页第九页，共49页。(dinz)n 电子(dinz) C=O：例：COHnp ps sH第9页/共49页第十页，共49页。能量第10页/共49页第十一页，共49页。分子中电子的能级和跃迁 第11页/共49页第十二页，共49页。2. n* transition 实现这类跃迁所需要的能量较实现这类跃迁所需要的能量较高，高， 吸收波长为吸收波长为150250nm，大部分在远紫外区，近紫，大部分在远紫外区

3、，近紫外区仍不易观察到。外区仍不易观察到。 含非键电子的饱和烃衍生物含非键电子的饱和烃衍生物(含含N、O、S和卤素等杂原子和卤素等杂原子(yunz)均呈现均呈现n* 跃迁。跃迁。如如CH3OH第12页/共49页第十三页，共49页。4. n* transition 这类跃迁发生在近紫外光区这类跃迁发生在近紫外光区, 一一般般(ybn)200 nm 。它是简单的生。它是简单的生色团如羰基、硝基等中的孤对电子色团如羰基、硝基等中的孤对电子向反键轨道跃迁。其特点是谱带强向反键轨道跃迁。其特点是谱带强度弱，摩尔吸光系数小，通常小于度弱，摩尔吸光系数小，通常小于100，属于禁阻跃迁。，属于禁阻跃迁。第13

4、页/共49页第十四页，共49页。 第14页/共49页第十五页，共49页。第15页/共49页第十六页，共49页。AA第16页/共49页第十七页，共49页。第17页/共49页第十八页，共49页。第18页/共49页第十九页，共49页。第19页/共49页第二十页，共49页。 超共轭效应超共轭效应(xioyng)比共轭效应比共轭效应(xioyng)的影响小的多的影响小的多第20页/共49页第二十一页，共49页。反式反式 大共轭体系大共轭体系 顺式顺式第21页/共49页第二十二页，共49页。分子中电子的能级和跃迁 第22页/共49页第二十三页，共49页。Using different wavelength

5、s of light through a constant concentration and thickness of the solution under test to measure the absorption degree of the solution under test on each wavelength light (absorbance), and then make the wavelength as the abscissa and the absorbance as the ordinate to map a curve. The material absorpt

6、ion capacity of different wavelength can be described by the curve , called absorption curve or absorption spectra. 第23页/共49页第二十四页，共49页。第24页/共49页第二十五页，共49页。UV-Vis Spectrometer第25页/共49页第二十六页，共49页。Radiation sourceMonochromatorSample containerDetectorreadout device 第26页/共49页第二十七页，共49页。1. 1. Radiation s

7、ource In the UV region or the visible region of the spectrum can emit continuous spectrum(200-1000 nm), with enough radiation intensity, good stability, long service life. There are two kinds of light source, thermal radiation light source and gas discharge light source.Visible light RegionVisible l

8、ight Region：as a light as a light source, its radiation wavelength range from 320 to 2500 source, its radiation wavelength range from 320 to 2500 nm.nm.Ultraviolet light RegionUltraviolet light Region： emit Continuous spectrum of 185 to 400 nm.Continuous spectrum of 185 to 400 nm.第27页/共49页第二十八页，共49页

9、。第28页/共49页第二十九页，共49页。入射狭缝(xi fn)：光源的光由此进入单色器； 准光装置：透镜或返射镜使入射光成为平行光束； 色散元件：将复合光分解成单色光；棱镜或光栅；聚焦装置：透镜或凹面反射镜，将分光后所得单色光聚焦至出射狭缝(xi fn)； 出射狭缝(xi fn)。第29页/共49页第三十页，共49页。第30页/共49页第三十一页，共49页。 （五）信号显示器（五）信号显示器 常用的显示器有检流计、微安计、电位常用的显示器有检流计、微安计、电位(din wi)计、数字电压表、记录仪、示波器及数据处理机等。计、数字电压表、记录仪、示波器及数据处理机等。第31页/共49页第三十二

10、页，共49页。光源光源单色器单色器参比参比样品样品检测检测器器显示显示器器 只有一条光路，通过变换参比池和样品池的位置只有一条光路，通过变换参比池和样品池的位置(wi zhi)，使它们分别置于光路来进行测定，使它们分别置于光路来进行测定简单，价廉，适于在给定波长处测量吸光度或透光度简单，价廉，适于在给定波长处测量吸光度或透光度，一般不能作全波段光谱扫描，要求光源和检测器具，一般不能作全波段光谱扫描，要求光源和检测器具有很高的稳定性。有很高的稳定性。第32页/共49页第三十三页，共49页。单色器参比样品检测器显示器斩光器光源2.Double-beam 2.Double-beam 双光束双光束 自

11、动记录，快速全波段扫描。可消除光源不自动记录，快速全波段扫描。可消除光源不稳定稳定(wndng)(wndng)、检测器灵敏度变化等因素的影响，特、检测器灵敏度变化等因素的影响，特别适合于结构分析。仪器复杂，价格较高。别适合于结构分析。仪器复杂，价格较高。第33页/共49页第三十四页，共49页。光源单色器单色器吸收池检测器斩光器用两种不同波长的单色光束交替照射到样品溶液用两种不同波长的单色光束交替照射到样品溶液(rngy)上，不需使用参比溶液上，不需使用参比溶液(rngy)，测得的是样品在两种波长下的吸光度之差，测得的是样品在两种波长下的吸光度之差将不同波长的两束单色光将不同波长的两束单色光(1

12、、2) 快速交替通过同一吸收池而后到达检测器。产生交流快速交替通过同一吸收池而后到达检测器。产生交流信号。无需参比池。信号。无需参比池。= 12nm。A=A2-A1=(2-1)bc=Kc第34页/共49页第三十五页，共49页。Qualitative and quantitative basisOrganic structure assisted analysis第35页/共49页第三十六页，共49页。1. qualitative analysisAt the same condition,It usually includes the determination of unknown mate

13、rial uv spectra, compared with the absorption spectrum of known standard material , analyzing the absorption spectral characteristics, such as absorption peak number, location, absorption valley, shoulder peak position, etc. If the molecular structure of the compounds is the same, they should have t

14、he same absorption spectra.Sample to be measured The same condiion The sample spectrumStandard material The standard spectrumAt a certain wavelength,the same substance in different concentrations have the different absorbance A ,and the difference of absorbance at At a certain wavelength,the same su

15、bstance in different concentrations have the different absorbance A ,and the difference of absorbance at Max was the largest. This characteristic can be used as the basis for Max was the largest. This characteristic can be used as the basis for quantitativequantitative analysis. analysis.第36页/共49页第三

16、十七页，共49页。 2.Quantitative analysis The basis:Lambert-Beers Law Lambert-Beers Law A= b c -lgT = b c high sensitivity： max：104105 L mol-1 cm -1； Generally,we measure A at the point of max in single component ,and then do the standard curve to get the best sensitivity. 第37页/共49页第三十八页，共49页。第38页/共49页第三十九页

17、，共49页。 1. structural information from UV-Vis To understand the degree of conjugation, the space effect, etc.,to determine the saturated and unsaturated compounds, isomers and conformation. The general rule of the information analysis of organic compound hair color system in the UV/Vis absorption spe

18、ctra is: if there have no absorption peak within the wavelength range of 200 750nm ,it may be a straight chain alkanes, cycloalkanes, saturated aliphatic compounds or olefin containing only one double bond. if there have a low intensity absorption peak within the wavelength range of 270 to 350 nm(10

19、100Lmol-1cm-1), (n* transition), it may contain a simple non conjugate and n-electronic chromophore,such as carbonyl.第39页/共49页第四十页，共49页。 若在20300nm波长范围内有中等强度的吸收峰则可能含苯环，假设有精细结构的话，可能是苯环的特征吸收。 若在210250nm波长范围内有强吸收峰，则可能含有(hn yu)2个共轭双键；若在260350nm波长范围内有强吸收峰，则说明该有机物含有(hn yu)3个或3个以上共轭双键。 若该有机物的吸收峰延伸至可见光区，则该有机

20、物可能是长链共轭或稠环化合物。第40页/共49页第四十一页，共49页。 (1) 确认max，并算出，初步估计(gj)属于何种吸收带； (2) 观察主要吸收带的范围，判断属于何种共轭体系；第41页/共49页第四十二页，共49页。第42页/共49页第四十三页，共49页。第43页/共49页第四十四页，共49页。Qualitative and quantitative basisOrganic structure assisted analysis第44页/共49页第四十五页，共49页。1. qualitative analysisAt the same condition,It usually in

21、cludes the determination of unknown material uv spectra, compared with the absorption spectrum of known standard material , analyzing the absorption spectral characteristics, such as absorption peak number, location, absorption valley, shoulder peak position, etc. If the molecular structure of the c

22、ompounds is the same, they should have the same absorption spectra.Sample to be measured The same condiion The sample spectrumStandard material The standard spectrumAt a certain wavelength,the same substance in different concentrations have the different absorbance A ,and the difference of absorbanc

23、e at At a certain wavelength,the same substance in different concentrations have the different absorbance A ,and the difference of absorbance at Max was the largest. This characteristic can be used as the basis for Max was the largest. This characteristic can be used as the basis for quantitativequantitative analysis. analysis.第45页/共49页第四十六页，共49页。 2.Quantitative analysis The basis:Lambert-Beers Law Lambert-Beers Law A= b c -lgT = b c high sensitivity： max：104105 L mol-1 cm -1； Generally,we measure A at the point of max in single component ,and then do the standard curve to