布鲁克红外光谱培训 课件

傅立叶红外光谱介绍 电磁波 GammaRay X Ray UV Infrared MicroWave ShortWave RadioWaves Energy eV Wavenumber cm 1 Wavelength m Visible 光与分子的作用 分子激发产生振动 振动的种类 伸缩振动 对称伸缩振动 不对称伸缩振动 例如 水 变形振动 水的红外图 1500 2000 2500 3000 3500 wavenumbercm 1 60 65 70 75 80 85 90 95 100 Transmission 正己烷 50多不同的振动 正己烷 指纹区 红外光谱分为三个范围 15 000cm 1 4 000cm 1 400cm 1 5cm 1 NIR MIR FIR 如何得到一张图 色散型红外光谱仪 傅立叶变换红外光谱仪 色散型红外光谱仪 Detector Detector 优点 不需要计算机 缺点 速度慢 光通量低 灵敏度低 S Nratio 傅利叶变换红外光谱仪原理 x Detector x L L x 例1 x 0 相长干涉 结果 1 Beampart 定镜 2 Beampart 动镜 x L L x 例2 x 1 2 相消性干涉 0 结果 1 Beampart 定镜 2 Beampart 动镜 x L L x example3 x constructiveInterference 0 Resultingsignal 1 Beampart fixed 2 Beampart movable x L L x example4 x 3 2 destructiveInterference 0 Resultingsignal 1 Beampart fixed 2 Beampart movable Mirrormotion Intensity 监测器信号 Frequence Intensity 光源 单色光源 单色光源的调制信号 EntstehungdesInterferogramms Frequence Intensity 9条单一频率的光源 检测器信号 Frequency Intensity 红外光源 X movingmirror Intensity 干涉图的来源 透射光谱 1 IntheemptysamplecompartmentanInterferogramisdetected TheresultoftheFOURIERtransformationisR Fourier Transformation 500 1000 1500 2000 2500 3000 3500 4000 wavenumbercm 1 0 10 0 20 0 30 0 40 Singlechannelintensity X movingmirror Detectorintensity 2 Asecondinterferogramisdetectedwiththesampleplacedinthesamplecompartment TheresultoftheFOURIERtransformationisS S showssimilaritiestothereferencespectrumR v buthaslowerintensitiesattheregionsthesampleabsorbsradiation Fourier Transformation 500 1000 1500 2000 2500 3000 3500 4000 wavenumbercm 1 0 10 0 20 0 30 0 40 Singlechannelintensity X movingmirror Detectorintensity 透射光谱 ThetransmissionspectrumT iscalculatedastheratioofthesampleandreferencesinglechannelspectra T S R 透射光谱 AbsorbanceTransmission Why Transmission Absorbance T S R Lambert Beer slaw AB log S R AB c b PrinciplelayoutofFT IRspectrometer x LayoutofanFT IRspectrometer TENSORseries Electronic Sourcecompartment Samplecompartment Sampleposition Detector Interferometercompartment AperturewheelFilterwheel NIR Source tungstenlampOpticalmaterial QuartzDetector Ge InGaAsMIR Source GlobarOpticalmaterial KBr ZnSeDetector DTGS MCTFIR Source Globar HglampOpticalmaterial PE CsIDetector DTGS Bolometer DifferencesbetweenNIR MIR FIR Opticalcomponents FourierTransformation FT Dataacquisitionresultsinadigitizedinterferogram I x whichisconvertedintoaspectrumbymeansofthemathematicaloperationcalledaFourierTransform FT ThegeneralequationfortheFourierTransformisapplicabletoacontinuoussignal Ifthesignal interferogram isdigitized however andconsistsofNdiscrete equidistantpoints thenthediscreteversionoftheFT DFT mustbeused S k I n x exp i2 k n N Thecontinuousvariablesxandhavebeenreplacedwithn Dxandk D representingthendiscreteinterferogrampointsandthekdiscretespectrumpoints Thefactthatwenowhaveadiscrete ratherthancontinuous function andthatitisonlycalculatedforalimitedrangeofn i e themeasuredinterferogramhasafinitelength leadstoimportanteffectsknownasthepicket fenceeffectandleakage TheFourierTransform x 高光谱分辨 低光谱分辨 添零 Thepicket fenceeffectoccursiftheinterferogramcontainsfrequencycomponentswhichdonotexactlycoincidewiththedatapointpositions k inthespectrum Theeffectcanbethoughtofasviewingthespectrumthroughapicketfence therebyhidingthosefrequenciesthatarebehindthepickets i e betweenthedatapointpositionsk Intheworstcase ifafrequencycomponentisexactlybetweentwosamplingpositions asignalreductionof36 canoccur Thepicket fenceeffectcanbereducedbyaddingzerostotheendoftheinterferogram zerofilling beforetheDFTisperformed Thisinterpolatesthespectrum increasingthenumberofpointsperwavenumber Theincreasednumberoffrequencysamplingpositionsreducestheerrorcausedbythepicket fenceeffect Generally theoriginalinterferogramsizeshouldalwaysbeatleastdoubledbyzerofilling i e zerofillingfactor ZFF oftwoischosen Zero fillinginterpolatesusingtheinstrumentline shape andinmostcasesisthereforesuperiortopolynominalorsplineinterpolationmethodsthatareappliedinthespectraldomain Zero fillingfactor2 Zero fillingfactor8 截趾函数 Inarealmeasurement theinterferogramcanonlybemeasuredforafinitedistanceofmirrortravel Theresultinginterferogramcanbethoughtofasaninfinitelengthinterferogrammultipliedbyaboxcarfunctionthatisequalto1intherangeofmeasurementand0elsewhere Thissuddentruncationoftheinterferogramleadstoasinc i e sin instrumentallineshape Foraninfinitelynarrowspectralline thepeakshapeisshownatthetopofthefigureontheright Theoscillationsaroundthebaseofthepeakarereferredtoas ringing or leakage Thesolutiontotheleakageproblemistotruncatetheinterferogramlessabruptly Thiscanbeachievedbymultiplyingtheinterferogrambyafunctionthatis1atthecenterburstandcloseto0attheendoftheinterferogram Thisiscalledapodization andthesimplestsuchfunctionisaramp or triangularapodization Thechoiceofaparticularapodizationfunctiondependsontheobjectivesofthemeasurement Ifthemaximumresolutionof0 61 Lisrequired thenboxcarapodization i enoapodization isused Ifaresolutionlossof50 comparedtothemaximumresolutionof0 61 L canbetolerated theHAPP GENZELor evenbetter 3 TermBLACKMAN HARRISfunctionisrecommended ABOXCAR noapodization BTriangular CTrapezoidal DHAPP GENZEL E3 TERMBLACKMAN HARRIS EvaluationofIRspectra 定性分析 1 鉴定未知物2 核对已知物定量分析 光谱评价 未知物的鉴定 a 通过光谱解析推出分子结构 不同有几类分子的红外吸收 烷烃 烯烃 芳香烃 内酯 卤化物 羧酸盐 酸酐 b 与标准谱库比较e g byusingOPUS Search 未知物的鉴定 identicalmaterial identicalIRspectrum Whatyouhave sample Whatyouneed referencelibrary Whatyoudo comparisonwithreferencelibrary Whatyouget identification 验证已知物 2 Calculateaveragespectrum thresholdvalues 3 Librarystructure validation 1 Measurereferencesample Wavenumber cm 1 Absorbance Wavenumber cm 1 Absorbance Referencelibrarystructure 1 Measurenewsamples 2 Comparewithlibrary Identifyingnewsamples 3 Identifymaterial Whatyouhave sample Whatyouneed calibrationset Whatyoudo comparisonwithcalibrationset Whatyouget concentrationvalueTherearetwodifferentformsofcalibration Univariatecalibration OPUS Correlatesjustonepieceofspectralinformation e g peakheightorpeakarea withthereferencevaluesofthecalibrationset Multivariatecalibration OPUS QUANT Correlatesconsiderablymorespectralinformation higherdegreeofprecision reducedchanceoferrorOPUS QUANTusesthePartialLeastSquares PLS Method Quantitativeevaluationofspectra 2 Buildcalibrationset QuantMethod 3 Validatecalibrationset 1 Measurecalibrationspectra Wa