欢迎来到天天文库
浏览记录
ID:48905244
大小:4.81 MB
页数:61页
时间:2020-02-01
《Chapter6-Atomic Absorption Spectroscopy.ppt》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
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:ΔO§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
此文档下载收益归作者所有