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1、AA分析之干扰及校正,干扰的主要类型,A.谱线干扰Spectral Line InterferenceB.解离干扰Vaporization InterferenceC.离子化Ionization InterferenceD.基体干扰Matrix InterferenceE.背景干扰Background Absorption,A.谱线干扰,1.干扰物与分析物之谱线重叠2.分析物谱线包含於干扰分子宽谱线中解決方法:1.减小狭缝宽度 Decrease Slit Width2.选用替换谱线Use Another Spectra Line3.采取化学分离Adopt Chemical Separation
2、,B.解离干扰,部份样品产生改变挥发速率之盐类，或干扰物与分析物产生不易裂解之热稳定物質，使分析物未完全成为自由原子。待测元素与其共存物质作用生成难挥发的化合物，致使参与吸收的基态原子减少。例：a、钴、硅、硼、钛、铍在火焰中易生成难熔化合物 b、硫酸盐、硅酸盐与铝生成难挥发物。解決方法：1.提高火焰温度Increase Flame Temperature2.释放剂Releasing Agent3.保护剂Protecting Agent 4.化学分离Chemical Separation,释放剂Releasing Agent:与干扰物形成更稳定之化合物，而释放出分析物。Ex:LaCl3 C2H2
3、/AirCa3(PO4)2 CaCl2 Ca0保护剂Protecting Agent:与分析物形成稳定且易挥发之化合物，而防止干扰。Ex:EDTA可去除检测Ca 時硫酸根及磷酸根之干扰。,C.离子化干扰,待测离子离子化势能很低，在火焰中极易离子化，发生电离反应，生成离子，不产生吸收，总吸收强度减弱，造成灵敏度降低电离电位6eV的元素易发生电离，火焰温度越高，干扰越严重，（如碱及碱土元素）解决办法：加入大量（100倍以上）更易离子化元素，例如 Na,K,Cs,Sr.来抑制分析物游离例如:C2H2/Air 测定Ba 时加入 2000 至 5000 ppm 的KCl,D.基体干扰,雾化过程中若待测样
4、品与标准样品溶液的粘稠性或表面张力不同，造成吸入或雾化效率不同。解決方法：1.使测试样品与标准样品溶液的成分条件越接近越好。在样品前处理时加入酸或其他试剂时，也需同时加入近似浓度于标准溶液中2.标准加入法(Standard Addition Method),标准加入法,标准加入校准曲线,典型的标准加入实例,E.背景吸收,由火焰中的共存成分（火焰本身或溶液共存）导致的宽带辐射.包括金属氧化物、氢分子、OH自由基和溶剂碎片等解決方法：1.D2 背景校正2.Zeeman 效应背景校正,氘灯背景校正原理,氘灯光路示意路,100%,100%,50%,50%,50%,50%,RBC,D2,HCL,Back
5、ground Correction,Deuterium Lamp Operation,Used to measure non-atomic absorptionUseful from 190-425nmFill gas is Deuterium(D2)Discharge current excites D2 gasHigh light emission through discharge aperture,Normal Range 190-300 nm,Lower HCL mA 300-425 nm,No D2 425-900 nm,氘灯随波长的发射强度变化,Zeeman 背景校正原理,Zee
6、man 效应,以橫向交流磁场为例：固定式偏振器仅让与磁场垂直的相位()光通過当磁场关闭时，原子吸收无Zeeman效应，此时所得的信号为背景吸收加原子吸收讯号当磁场开启时，原子吸收产生Zeeman效应，此时吸收波長不变的 成分由於于相位与磁场平行而被偏振器偏折，而相位与磁場垂直之成分 由于波长改变，从而偏离空心阴极灯提供的共振波长，不会产生吸收。因此，此时所获得的信号，仅为背景吸收。以磁场关闭时所获得的信号扣除磁场开启时所获得的背景信号，即可得原子吸收信号,Zeeman 背景校正原理,Zeeman 裂解效应,Zeeman 效应,Zeeman 效应背景校正,光的偏振,Field Vector of
7、 Light,未被偏振的光,完全被偏振的光,Zeeman 原理示意图,真实的原子吸收信号即是以总的吸光度（磁场关闭时）减去背景吸光度（磁场关闭）,石墨炉中基体干扰的校正,热解涂层的作用,电镜扫描图:无热解涂层的表面 有热解涂层的表面,什么是平台?,平台的作用,Time,Abs,From Wall,From Platform,Internal Gas Temperature,集成平台,From:Schlemmer,Atomic Spectroscopy,1996,原子化时管壁和平台的温度,基体改进剂,为什么要用基体改进剂?何时需要?如何选择基体改进剂?有“万能”基体改进剂?,化学改进剂Chemi
8、cal Modifier,以化学方式改变分析元素的挥发性和/或基体組成。Chemically alters the volatility of the analyte element&/or the bulk matrix constituents降低基体或背景干扰。Used to reduce matrix or background interferences.可能增加或降低灵敏度。Can enhance or degrade sensitivity.,化学改进剂Chemical Modifier,化学改进剂改变分析元素或基体的化学特性。Chemical modifiers chemica
9、lly alter behaviour of either analyte or matrix.降低待測元素揮發性，以提高灰化溫度。幫助基体挥发（因為灰化溫度提高）使樣品中分析元素形成單一化合物，而非各式不同之分子物種。將原子化溫度提高（或降低）。Shift atomization temperature to higher(or lower)value.,基体改进剂的作用,减少待测物的挥发性增加基体的挥发性提高易挥发性元素的原子化温度,减少待测物的挥发性,Se+Pd/Mg(NO3)2,Se with no modifier,增加基体的挥发性,NH4NO3 对NaCl的挥发性的影响NaCl+N
10、H4NO3 NaNO3+NH4Cl 挥发温度 NaCl.1413oC NH4NO3.210oC NaNO3.380oC NH4Cl.335oC,Pd/Mg基体改进剂的作用,From:Schlemmer,Atomic Spectroscopy,1996,使用Pd/Mg(NO3)2 和H2,Pd in reducing environment enhances performance1991,EPA EMSL publishes method 200.9(Revision 1.2)Creed et al.,1992;Environ.Sci.Technol.Revision 2.2 publishe
11、d in 1994,EPA Method 200.9,Designed primarily for the analysis of waters including:drinking,surface,ground,and wastewatersPrinciples of analysis may also be applied for the analysis of sediments,sludges,and soilsWhere sample digestion is required a mixed acid digestion using HCl and HNO3 is employed
12、,EPA Method 200.9,Pd/Mg(NO3)2 used as the modifier for all elementsA mixture of 95%Ar/5%H2 is used as the internal gas during the dry and pyrolysis stepsIf lower detection limits are required for certain matrices,multiple injections(preconcentration)can be utilized,内外保护气,ArgonOxygen or air:useful in
13、 ashing samples in situ that may be high in organic matter;ashing temperature usually restricted to 600oC or lowerArgon/Hydrogen:95%Ar/5%H2 often useful in eliminating chloride interference;see EPA Method 200.9,2%HCl 和Pd/Mg(NO3)2 做基体改进剂对待测元素的影响,As,Sn,Pb,Tl,From:Creed et al.,Environ.Sci.Technol.1992,
14、2%HCl和Pd/Mg(NO3)2、Ar/H2做基体改进剂对待测元素的影响,As,Sn,Tl+Pb,From:Creed et al.,Environ.Sci.Technol.1992,Pyrolysis Curve for Tl in SRM City Waste Incineration Ash,From:Schlemmer,Atomic Spectroscopy,1996,Se 的石墨炉温度程序,Conditions:20 L sample volume+10 L diluent volume5 L modifier 0.3%Pd/0.2%Mg(NO3)2Injection temp.o
15、f 120 oC,“万能改进剂“Pd/Mg(NO3)2 和 Ar/H2,H2 is effective in keeping Pd reduced within the tubeEliminates many of the interferences caused by introducing HCl acid in furnace digestionsAnalyte spike recoveries may improve even if the mixed acid digestion is not employedRugged”furnace programs possible,废水中P
16、b的测定，1000 ppm Pd基体改进剂(灰化 1000,原子化 2000),废水中Pb的测定1000 ppm Pd基体改进剂(原子化2400),常见基体改进剂,EPA 所建议基体改进剂,元素 基体改进剂 Sb3%NH4NO3As1000mg/l Ni/5%HNO3Cd1%NH4H2PO4Pb1%H3PO4Se 1000mg/L Ni/5%HNO3Th 1000mg/L Pd,Note:EPA list of modifiers for Solid waste 846 method,使用基体改进剂后需要改变.,更高的灰化温度更长的灰化时间更高的原子化温度一样的优化原则和平台石墨管类似,不同基
17、体改进剂下的灰化温度,影响参数,Analyte Sample Matrix Sample Volume Injection Rate Modifier Used Modifier Concentration Modifier Volume Dry Temperatures Dry Heating Rates Dry Hold Time Dry Gas Flows,Ash Temperatures Ash Heating Rates Ash Hold Times Ash Gas Flows Atomize Temperatures Atomize Heating Rates Atomize Ho
18、ld Times Atomize Gas Flows Clean Out Steps Cool Down Steps,基体改进剂注意事項(1),GTA加熱速率需改變以進行反應GTA heating rates must allow reactions依需求決定濃度Individual factors determine concentration使用锋面积定量（並非絕對）Peak area may be more suitable改變灰化及原子化溫度Ash&atomization temperatures vary适当的体积及混合方式 Proper volume&mixing importan
19、t1:4 ratio of modifier to sample,基体改进剂注意事項(2),Minimal contaminationNo precipitationReducing agent used with palladiumOnly use if neededUse as little as needed,基体改进剂注入方式,Modifier can be 预先进样 into graphite tube(particularly if precipitate forms)Usual to dry modifier before adding sample共进 with the sam
20、pleModifier volume should be half that of sample volumeensures thorough mixing in the graphite tube预混合 with sample before injection,Pd 所适用的元素,-Pd the Universal Modifier,采用Pd为基体改进剂时的灰化温度(Metalloids),采用Pd为基体改进剂时的灰化温度（过渡金属）,Pd 基体改进剂的注意事项,Proper mixing with analyte importantFor effectiveness Pd must be reduced to Pd metalPd is easily reduced by ascorbic acid、citric acid and hydroxylamine hydrochlorideFurnace heating rate must allow reactionsIndividual factors determine Pd amountPeak area more suitable in some casesAtomization temperatures 2300,更多的应用请参考,
