ATOMIC ABSORPTION SPECTROMETER

SELİN CANSU ÖZTÜRK ŞEYMA ATAKUL

SEZİN GÜNER

ATOMIC ABSORPTION SPECTROMETERIntroduction Invention Working Principle of AASInstrumentationInterferences & Correlation MethodsApplications

INVENTIONIntroduced in 1955 by Alan Walsh in AustraliaFirstly used for mining, medical

treatment&agricultureAlan Walsh(1916-1998)

http://www.science.org.au/academy/memoirs/walsh2.html

PROPERTIES OF AASThe most widely used method in analysis of

elementsBased on the absorption of radiationSo sensitive (ppb)Quantitative analysis

WORKING PRINCIPLE OF AAS Electrons promote to higher orbitals for a

short amount of time by absorbing a energy M + hv → M*Relises on Beer-Lambert Law A= a.b.c

INSTRUMENTATION

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LIGHT SOURCES Hollow Cathode Lamps Anot-Tungsten wireCathode made from the element of interest

(Na,K,Ca..)Argon or neon gas

http://www.safir.be/AAS.ht

LIGHT SOURCES Electrodeless Discharge LampTypically argon gas at low pressure Narrower line width Not prefered

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ATOMIZATIONCompounds making up the sample are

broken into free atoms.High temperature is necessaryBasic two types

-Flame atomizer-Electrothermal atomizer

TYPES OF ATOMIZERS FLAME ATOMIZERSimplest atomizationConverts analyte into free atoms of vapor

phaseFlammable &caustic gasesNot has an inert medium (−)Short analysis time (−)

TYPES OF ATOMIZERS ELECTROTHERMAL ATOMIZERA cylindirical graphite tubeInert gas medium (Argon gas)Longer anlaysis time than flameSuperior sensitivity, high accuracy

MONOCHROMATORAlso it is called wavelengh selectorSelect the specific wavelenghtPolychromatic light →monochromatic lightSimple one is enough for AAS

DETECTOR Electromagnetic waves → electric currentThe most used one Photomultiplier tubeHave fast response times

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CALIBRATION TECHNIQUES

• Two main techniques

Calibration curve methodStandart addition method

CALIBRATION TECHNIQUES CALIBRATION CURVE METHOD

Draw a graphHave two or more variables -One is set at known values -One is measured response

Most convenient for a large number of similar samples analysis.

CALIBRATION TECHNIQUES

An example of calibration curve method

CALIBRATION TECHNIQUES STANDART ADDITION METHOD

To measure the analyte concentration in a complex matrix.

Most convenient for small number of samples analysis

Prevent effect of chemical & spectral interferences

INTERFERENCES

Causes higher or lower absorbance value

Two major groups

Chemical Interferences

Spectral Interferences

CHEMICAL INTERFERENCES

The most common one in flame atomizer.

Consequence of chemical reactions.

Reduce amount of oxygen in flame to overcome

SPECTRAL INTERFERENCESAbsorption or emission of the radiation at

the same wavelength

Radiation which is absorbed→pozitive errors

Radiation which is emmitted→negative errors

SPECTRAL CORRELATION METHODS TWO-LINE CORRELATION METHODSelect two linecharacteristic wavelength of analytevery close to analyte line but not absorbed by

analyte

Measure the difference between two lines

SPECTRAL CORRELATION METHODS CONTINUUM SOURCE CORRELATION METHODSelect two lampsDeuterium lamp & hollow cathode lampWhen hollow cathode lamp is used total

absorbace is measuredWhen deuterium lamp is used only

background absorption is measuredMeasure the difference between two lines.

SPECTRAL CORRELATION METHODS ZEEMAN EFFECT CORRELATION METHODPresence of magnetic field.Splitting of spectral lines.

CONCLUSIONOne of the most important technique in

quantitative analysisIt is based on the absorption of radiationMeasurements could be done at ppb levelsIt’s widely used methodThe preparation of the sample is usually

simple and rapid

CONCLUSIONThere are many adventagesHigh sensitivity [10-10 g (flame), 10-14 g (non-flame)] Good accuracy (Relative error 0.1 ~ 0.5 % ) High selectivity

APPLICATIONS OF AASWater analysis (e.g. Ca, Mg, Fe, Si, Al, Ba

content)Food analysisAnalysis of animal feedstuffs (e.g. Mn, Fe, Cu,

Cr, Se,Zn)Analysis of soilsClinical analysis (blood samples: whole blood,

plasma,serum; Ca, Mg, Li, Na, K, Fe)

REFERENCES

http://www.scribd.com/doc/10513921/Atomic-Absorption-Determination-of-Zinc-and-Copper-in-a-Multivitamin

http://www.hemlin.pp.se/USstarten.htmlhttp://www.learn-english-today.com/business-

english/presentations-phrases.htm

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