Chapter6-Atomic Absorption Spectroscopy.ppt

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1、Chapter6AtomicAbsorptionSpectrometry（原子吸收光谱）AAS原子吸收分光光度计（PerkinElmer)●Basicprincipleofatomicabsorptionspectrometricanalysis●Structureofatomicabsorptionspectrophotometer●Interferenceandelimination●Quantitativeanalyticalmethods●Sensitivity,characteristicconcentrationanddetectedlimit●briefintrod

2、uctionofatomicfluorescencespectrometry(AFS)掌握原子吸收光谱分析法的基本原理，了解原子吸收光谱仪的构造，重点掌握原子吸收分光光度定量分析方法。Outlines太阳光暗线1802年Wollaston发现太阳光谱的暗线；1859年Kirchhoff和Bunson解释了暗线产生的原因；暗线是由于大气层中的钠原子对太阳光选择性吸收的结果§1.InstroductionofAAS1.1HistoryHollowCathodeLamps1955年Walsh发表了一篇论文“Applicationofatomicabsorptionspectrometr

3、ytoanalyticalchemistry”,解决了原子吸收光谱的光源问题，50年代末PE和Varian公司推出了原子吸收商品仪器。空心阴极灯火焰棱镜光电管1.2CharactersofAASLittleinterferenceand/ormatrixeffectsAccurateandpreciseanalysisApplicationofmostelementsSimpleoperationandlow-cost1.3PrincipleofAASAtomicvaporabsorbtheradiationemittedbythespecialsource,theabsorpt

4、ionisproportiontothenumberoftheatomsTerms:Resonance-Absorption(共振吸收）表征吸收线轮廓（峰）的参数：中心频率O（峰值频率）：最大吸收系数对应的频率或波长;中心波长:λ（nm），半宽度：ΔO§2.Lineprofile(轮廓)ofatomabsorption一束不同频率强度为I0的平行光通过厚度为l的原子蒸气，一部分光被吸收，透过光的强度Iv服从吸收定律LinebroadeningcausedbyP387(1)Naturalwidth自然宽度10-4Å(2)Dopplerbroadeningifanatomemit

5、sradiationwhilemovingtowardthedetector,thewaveswillbecompressed,andthewavelengthwillbeshorterifanatomemitsradiationwhilemovingawayfromthedetector,thewaveswillstretchedout,andthewavelengthwillbelongerrelatedeffectforabsorption光子观测光子观测（0+D）（0-D）可见，Doppler变宽与谱线波长、相对原子质量和温度有关，多在10-3nm数量级1

6、1Chapter8(3)Pressurebroadening（压力变宽）CollisionamongatomscausingthechangingofenergyLorentzbroadening：atomsofdifferentelementsHoltmarkbroadening：collisioninatomsofoneelementLorentz变宽与Doppler变宽有相同的数量级，也可达10-3nm。(4)自吸变宽(5)electricandmagneticfieldeffects§3.Measuringofatomicabsorption(1)IntegralAbso

7、rption积分吸收IntegralabsorptionisproportionaltoN0DifficultiesinmeasuringoftheintegralabsorptionResolutionPowerofintegratorformeasuringtheabsorptionSensitivityofthedetectorformeasuringtheabsorption若用一般光源照射时，吸收光的强度变化仅为0.5%。灵敏度极差(2)Peakabsorption峰值