原子吸收光谱仪 (2).ppt
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1、原子吸收光谱仪前言l由Alan Walsh,于1954年发表第一台原子吸收光谱仪(AA)。What is“AA means lThe First“A means:Atomic 原子的lThe Atom comes from the“hot!lWe need the 火焰 or 电热lThe Second“A means:Absorption 吸收l光被吸收了,we need the lamp 理论篇Atomic Spectroscopy 理论篇 ExcitedExcited states statesE En ne er rg gy yE En ne er rg gy y Ground sta
2、te Excited stateGround state Excited stateAtom NaAtom NaAtom FeAtom Fe原子于原子化区中均是处于基态原子于原子化区中均是处于基态,当受到原子线照射时当受到原子线照射时,相同元素才会提升能阶相同元素才会提升能阶原子均有其唯一性的原子组态原子均有其唯一性的原子组态原子均有其唯一性的原子组态原子均有其唯一性的原子组态Na 线 Ground state Excited stateGround state Excited stateAAS 原子吸收光谱仪 火焰式ppm,sub ppbppb爐管式Beers Law:Absorbance,
3、A is proportional to concentrationA=log10 Io/It A=a b c,b:beam path,c=concentrationI=I0-(IAA+B)Excited StateAtom absorbs someof the incident lightGround StateI0入射原子线通过原子化区之入射原子线之剩余强度原子化区 理论篇Atomic Spectroscopy 理论篇 Concentration vs AbsorbanceI0B0.00000.07350.12570.25340.0ppm2.5ppm5.0ppm10.0ppm10000 个
4、光强10000 个光强500 个光强100 个光强10 个光强HollowHollowcathodecathodelamplampsourcesourceSpray chamberSpray chamberand and nebulisernebuliser Flame orFlame orgraphitegraphitefurnacefurnaceatom cellatom cellMonochromatorMonochromatorProcessing Processing electronicselectronicsData processingData processingand in
5、strumentand instrumentcontrolcontrolPhotomultiplierPhotomultiplierdetectordetector火焰式石墨炉Bandpath Atomic Spectroscopy 理论篇A=-Log(I/I0)空液,Blank2.5ppm5ppm10ppmAbs.I0IConc.HollowHollowcathodecathodelamplampsourcesourceSpray chamberSpray chamberand and nebulisernebuliser Flame orFlame orgraphitegraphitefu
6、rnacefurnaceatom cellatom cellMonochromatorMonochromatorProcessing Processing electronicselectronicsData processingData processingand instrumentand instrumentcontrolcontrolPhotomultiplierPhotomultiplierdetectordetector火焰式石墨炉Bandpath Atomic Spectroscopy 理论篇IIIIIIHollow Cathode LampHollow Cathode Lamp
7、 ProcessesAr+M0M0M*Ar+M*M0l(-)(-)(-)SputteringExcitationEmissionElectrical potential applied between cathode and anodeMetal atoms dislodged and excited by ionised argon filler gas;decay back to ground state results in emission at a specific wavelength(s).Lamp DriftHCL Beam 渐渐增强的,所以有两种因应方式:Single Bea
8、m:等Double Beam:立即记忆当时的强度TimeIntensitySample/Sample/火焰火焰绕过火焰纪录强度绕过火焰纪录强度Stockdale OpticsFurnaceToroidMirrorFlame Toroid MirrorPlane MirrorRear BeamSelectorFurnacePlane MirrorFlameHCL CarouselD2 Lamp火焰炉管Atomic Spectroscopy 理论篇Concentration sensitivity increased by 1000 X relative to flame Concentratio
9、n sensitivity increased by 1000 X relative to flame atomizeratomizerFlame TypesFlame TypeFlame TemperatureFuel Flow RateOxidant Flow RateBurner SizeAir/Acetylene2450C0.8-2.3L/min8L/min50 or 100mmNitrous Oxide/Acetylene3200C3.8-5.0L/min10L/min50mm onlyBurnerslExcellent corrosion resistancelSlot desig
10、n optimised for high dissolved lsolids sampleslAutomatic spark ignition systemlUniversal 50mm slot as standardSpray ChamberBurner Jaw Profile原子化区FlameFurnaceProblem II Light Light absorption from the HCLabsorption from the HCLInstrument bandpass0.2 nm0.002 nmAbsorption profile widthHollow cathodelam
11、p emission共振光谱吸收共振光谱吸收共振光谱吸收共振光谱吸收(Absorbance=area of(Absorbance=area of(Absorbance=area of(Absorbance=area of overlap)overlap)overlap)overlap)(i)I I0 0IAAIAAI I(I0 lost)(I0 lost)光折射光折射粒子阻挡粒子阻挡分子吸收分子吸收B:B:B:B:理论篇 I0波长等于多少波长等于多少波长等于多少波长等于多少强度等于多少强度等于多少强度等于多少强度等于多少讯号是否样品讯号是否样品讯号是否样品讯号是否样品?讯号是否等于样品I0BA
12、:0.0022,0.0019,0.0023A:0.0335,0.0351,0.03280.12570.25340.0ppm2.5ppm5.0ppm10.0ppm10000 个光强500 个光强100 个光强10 个光强 Light absorption from 氘灯Xxx.32 0.005 nm原子吸收线(ii)Instrument bandpass0.2 nm0.002 nmAbsorption profile width以连续波长来量测所有的背景值氘灯氘灯氘灯氘灯 170-450 nm170-450 nm170-450 nm170-450 nm(I0 lost)(I0 lost)光折射光
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