Emission Spectroscopy

Emission Spectroscopy Based upon Plasma, Arc, and Spark Atomization ArcArc Higher TemperatureHigher Temperature Lower interelement Lower interelement

interferenceinterference Single set of excitation Single set of excitation

conditions can excite conditions can excite multiple elementsmultiple elements

Permit low detection limits Permit low detection limits for refractory complexesfor refractory complexes

Larger linear rangeLarger linear range Can directly measure hard to Can directly measure hard to

measure samplesmeasure samples

FlameFlame Simpler, less Simpler, less

expensive expensive instrumentationinstrumentation

Lower operating costsLower operating costs Greater reproducibilityGreater reproducibility

Emission Spectroscopies Cont.

Plasma (def.) Electrically conducting Plasma (def.) Electrically conducting gaseous mixture containing significant gaseous mixture containing significant concentrations of cations and electronsconcentrations of cations and electrons

ICP and DCPICP and DCP

Inductively Coupled Plasma

Inductively coupled Inductively coupled means that the plasma means that the plasma is generated due to is generated due to differences in the differences in the magnetic field and magnetic field and currentscurrents

Temp. very hot (4000-Temp. very hot (4000-8000K)8000K) Good & badGood & bad

Direct Current Plasma (DCP)

Plasma forms by Plasma forms by bringing graphite and bringing graphite and W electrodes in W electrodes in contact with one contact with one anotheranother

Temp @ core 10,000KTemp @ core 10,000K

in viewing region in viewing region 5000K5000K

ICP DCP Comparison

DCP is an order of DCP is an order of magnitude less magnitude less sensitive than ICPsensitive than ICP

Similar Similar reproducibilitiesreproducibilities

DCP requires less ArDCP requires less Ar

Auxillary power less Auxillary power less expensive in DCPexpensive in DCP

Graphite electrode Graphite electrode must be replaced every must be replaced every couple of hourscouple of hours

Comparison of Plasma to Flame Emission Sources Plasma sources offer significantly better Plasma sources offer significantly better

quantitative data than do other flame quantitative data than do other flame emission sourcesemission sources

- High stability- High stability

- Low noise- Low noise

- Low background- Low background

- Freedom from interferences- Freedom from interferences

Comparison between Atomic Absorption & Emission Techniques

AASAAS AESAES

InstrumentsInstruments Requires HC lamp for each Requires HC lamp for each elementelement

No high quality MC requiredNo high quality MC required

Flame/ sample is sourceFlame/ sample is source

Requires high quality MCRequires high quality MC

Operator SkillOperator Skill

Bkgd.CorrectionBkgd.Correction

Prec. & Prec. & AccuracyAccuracy

InterferencesInterferences

Detection limitDetection limit


AASAAS AESAES





Operator SkillOperator Skill Lower skillLower skill Higher skillHigher skill

Bkgd.CorrectionBkgd.Correction





AASAAS AESAES






Bkgd.CorrectionBkgd.Correction Harder to doHarder to do Easier to doEasier to do





AASAAS AESAES








Unskilled betterUnskilled better

Same for skilledSame for skilled

Unskilled worseUnskilled worse




AASAAS AESAES











InterferencesInterferences Spectral interferences corrected Spectral interferences corrected in AESin AES

Chemical interferences Chemical interferences on AE (flame) bad, on AE (flame) bad, plasma eliminatedplasma eliminated



AASAAS AESAES











InterferencesInterferences Spectral interferences corrected Spectral interferences corrected in AESin AES

Chemical interferences Chemical interferences on AE (flame) bad, on AE (flame) bad, plasma eliminatedplasma eliminated

Detection limitDetection limit Flame some metals better on Flame some metals better on AA than AESAA than AES

Plasma comparable to Plasma comparable to flame for some metals, flame for some metals, other metals plasma other metals plasma betterbetter

Comparison of Metal Spectroscopic Techniques

Performance Performance CriteriaCriteria

Flame Flame AAAA

Electrothermal Electrothermal SamplingSampling

Flame Flame AESAES

DCPDCP ICPICP

Dynamic Dynamic rangerange

limitedlimited limitedlimited widewide widewide WideWide

Qualitative Qualitative analysisanalysis

Elemental Elemental rangerange

Trace Trace analysisanalysis



Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP




poorpoor poorpoor excellentexcellent excellentexcellent excellentexcellent





Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP






excellentexcellent excellentexcellent excellentexcellent excellentexcellent excellentexcellent




Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP











Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP









Comparison of Metal Spectroscopic Techniques continued


Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP

Matrix Matrix interferncesinterfernces

highhigh highhigh highhigh lowlow lowlow

Spectral Spectral InterferenceInterferencess

Precision & Precision & AccuracyAccuracy

CostsCosts



Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP




lowlow lowlow lowlow moderatemoderate highhigh


CostsCosts



Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP






Better Better for for unskilledunskilled

Same Same skilledskilled

Worse Worse for for unskilled unskilled same same skilledskilled

CostsCosts



Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP






Better Better for for unskilledunskilled

Same Same skilledskilled

Worse Worse for for unskilled unskilled same same skilledskilled

CostsCosts $$$$ $$$$$$ $$ $$$$$$ $$$$$$$$



Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP

Costs Costs

InstrumentatInstrumentationion


MaintenanceMaintenance

Sample Sample PreparationPreparation

Operator Operator skillskill



Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP

Costs Costs



MaintenanceMaintenance lowlow lowlow lowlow moderatemoderate highhigh





Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP

Costs Costs





moderatemoderate moderatemoderate lowlow moderatemoderate moderatemoderate




Flame Flame AAAA


Flame Flame AESAES

DCPDCP ICPICP

Costs Costs





moderatemoderate moderatemoderate lowlow moderatemoderate moderatemoderate


lowerlower higherhigher higherhigher higherhigher higherhigher

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Emission Spectroscopy