近红外光谱原理.

1、s1近红外光谱原理及应用主要内容近红外光谱原理-近红外光谱与化学计量学近红外模型的评价第一部分近红外光谱原理什么是近红外光12,800 cm1 (780 nm)X-射线ML丫射线做波Radio. TV 上 线电波3,960 cm i (2,526 nm)迖红外娠动-!UOQOB3U-原广核 转变分（转动波长度量单位：纳米nm与波数cm1cm _ 10znm800nm _ 800nm1cm=107nm波长800nm转换为cnrnm = 107/cm-1 cm-1 = 107/ nm=12500cm 1振动吸收光谱的理论E = Et + Ev + Er + Ee分子能量平动 振动 转动电子运动辐射

2、光的能屋与振动跃迁能量和同时，辐射光被物质 分子吸收。能ht接近ev近红外光能吊引起分子振动能级的变化， 乂称振动光谱。近红外光谱产生原理近红外吸收光谱特征u物质在近红外谱区的吸收重叠严重.近红外的合频振动的吸收系数比中红外基频振动吸收弱1-5个数量级.Water SpectrumcOUBqJosqvWavenumber cm 1不同化合物基团在近红外区的吸收谱带Firsi OrftMTaoe RegiiwTtiril (XtHton Fkgtiihoar InfraredLksttd AsyHOD 1OT0IMOX(D1XK17001800BCD2000Z1002200230024002M0

3、33)K2714J仙67Z SM256S6S263WOO4J624354348416?SOO10J 11111 1WOO !91水分、脂肪、蛋白吸收谱带High watercontent宙脂肪XHigh fat :ontentprotein:ontent近红外光与物质的相互作用吸收 全反射 absorption specula reflectance透射transmitta nee滋（反）射Diffusescatteringreflectance光源单色縉或干涉仪光源单色器或干涉仪样品检测R9透漫射式Near-IR Trans-Reflectance (NITR)单色器或干汾仪样品近红外的采样

4、方法透射式Near-IR Transmittance (NIT)漫反射式NearIR Reflectance (NIR)近红外的分光方法滤光片型光源样品检测器滤光片滤光片型仪器的优缺点优点：1. 制造成本低，推广面大：2. 体积小，可以便携。缺点：1. 滤光片的带宽较宽（一般10nm）。2. 滤光片透光的光谱中心点难以保证。3. 同一波长滤光片的带宽和透过率难以保证一致。4. 信息最少，只能作为专用仪器。5. 得到的不是连续光谱，不能对光谱进行预处理（如平滑、求导等）。光栅扫描型狭缝光源光栅挟缝检测器光栅扫描型B狭缝光源光栅挟缝检测器光栅扫描型狭缝光源检测器光栅型仪器的优缺点优点：1. 结构不

5、复杂.容易制造。2. 连续光谱仪.可以作为研究级仪器。缺点：1. 使用单色器.狭缝的限制使其分辨率和灵敏度不够高2. 波长准确度使用外部校准，加之分辨率低，波长准确度差（最好为 +/-0. 2nm） o3. 使用单色器对光路要求严格，仪器扩展能力受到很大的限制，4. 自然界的杂散光会影响测试结果。5. 由于分光需光栅转动.扫描速度慢。阵列检测器阵列检测器阵列检测器型的优缺点优点：1. 无移动光学部件，易实现小型化。2. 扫描速度快.适合现场分析。缺点：1. 分辨率较低2. 一致性比光栅扫描型更难保证。3. 受杂散光影响SampleSourceDetectorGratingMEMS Micro

6、electro mechanical systems 微电子机械系统SourceTeO2 CrystalSampleDetectorsReferencemonochrom Light (extraordinary Beam)non-scattered Lightmonochrom. Light (ordinary Beam)Mems ChipAOTF acousto optical tunable filter 声光可调滤光器RF-InputMichelson InterferometerMovableMirrorBeamsplitterBSourceBeamsplitterDetectorM

7、ovable mirror M2Fixed mirror Ml穹 DetectorS|/WWVWWWW11/WVWVVWVWWWV-C2VC-Fixedmirror MlMovable miiror M2wcm】AxSourcemmmmI tetnr nllx=0L + AxBeamsplitterBeamsplitterDetectorSpcctrumcasc-DetectorFixed mirror MlOftlcil m irdatiua.fKPsSpcxrtruni of 9 Kgl frguciKie,FfcuencyMichelson InterferometerMovableMi

8、rror SourceBeamsplitterDetector傅立叶变换型的优缺点优点：1. 光通量大，灵敏度高，高信噪比。狭缝2. 高分辨率。3. 咼测昆精度a4. 测量速度快。5. O O O缺点:1.平面反射镜.如果在快速扫描过程中发生晃动和偏转.造成干涉信号 降低，灵敏度下降。Cube-Corner InterferometerPlane Mirrors in a classical Michelson Interferometer Cube-Corner Mirrors in a ROCKSOLID-InterferometerCube-Corner m i r rorsThe RO

9、CKSOLID philosophy is to eliminate possible sources of measurement errors rather than to try to correct for them after the measurement第二部分近红外光谱与化学计量学朗伯比尔定律Sample右=intensity of reference beamI intensrty of sample beam d sample thickness c concentration c = molar absorptlon coefficientTransmission TAb

10、sorpti on = A=log = Ecd透过率、吸光度与浓度的关系Transmission (Reflectance)not linearAbsorbanceLog I()linearThe Calibration ModelsB线性冋归D2O10COOH1200KOO15D018002000曲inmj22002400cc oQuant itat i ve Ana lysis; Regress i on2603BWavelengthConce ntrationThe Calibration Models1一个波长点a = b + mxC = B0+BI *AC = Con centrat

11、ionBo= Bias (intercept, offset)Bi = Regression Coefficent at wavelength 1A1 = Absorbance at wavelength 1近红外光谱的重叠The CaIibrat ion Mode Is多元线性冋归2.两个波长点C = B（）+ B * A + B2 * A2*three dimensions !3n个波长点C = Bo+B| *A| + B?*A 4- + B,* An n+1 dimensions !How to f i nd the bands you need?About how many data

12、po ints are we talking about?Start WL (nm or cm-1)End WL (nm or cm-1)Optical resolutionUseful datapoints11002500101409090400016318909040003215990904000863690904000412739090400022545Optical resolution Dispersive system in cm-1About how many data points are we taIk about?Principle Comp orient Analysis

13、 (PCA)Matr ices and vectorsFactor Analysis of spectraFactor Analysis breaks apart lhe spectral data into the most comm on spectral variati ons (factors, loadings, principal components) and the corresponding scaling coefficients (scores)光谱矩阵载荷dldata matrix:spectra of data pointsscores: loadings:score

14、s for each spectrum ( ) loadings of data points ( )西红柿鸡蛋vs主成分B1 x西红柿3x鸭蛋3x水0.2 x2x西红柿2x鸡蛋0.1 x 水05x葱2x西红柿1 x鸡蛋 25x水 0.1 x 葱Factor Ana lysisBscoresctor 15.216ctor 2-016ctor 31.73E-02ctor 4“ 52E-02ctor 53.17E-02ctor 15.95ctor 20.103ctor 34.97E-04ctor 44.33E-02ctor S5.SSEO3ctor 17.731ctor 20699ctor 33.S7E-04ctor 41.16E02ctor 5-2.04E-02ctor 15.768ctor 20.693ctor 32.97E-02ctor 4-3.76E-03ctor 51.27E02ctor 17.13 ctor 20.441ctor 3-3.75E-02ctor 4-9.54E-03ctor 54.46E-03FaFaFaFaFaFaFaFaFaFaF zFdF FFaFaFaFaFflfactors光谱7.731+-0.699+3.67E-04+-1.15E-02+204E02spectrumReconst