A BRIEF ABOUT ATOMIC ABSORPTION SPECTROSCOPY.ppt

AAS is an analytical technique used to determine how much of certain elements are in a sample. It uses the principle that atoms (and ions) can absorb light at a specific, unique wavelength. When this specific wavelength of light is provided, the energy (light) is absorbed by the atom.

1. Dr. Rachana Choudhary
Department of Microbiology
Shri Shankaracharya Mahavidyalaya Junwani Bhilai
ATOMIC ABSORPTION SPECTROSCOPY

2. CONTENT
•INTRODUCTION
•PRINCIPLE
•INSTRUMENTATION
•ADVANTAGE AND DISADVANTAGE
•APPLICATION
•REFERENCE

3. INTRODUCTION
•A.Walshin1955,fisrtlyintroducedtheAAS.
•AASdeterminesthepresenceofMetalsinliquid
sample.metalincludeFe,Cu,Al,Ca,Zn,Cdand
manymore.
•AASisthemostpowerfulinstrumentaltechnique
forthequantitativeandqualitativedetermination
oftracemetalsinliquids.
•AASisatechniquefordeterminingthe
concentrationofaparticularmetalelementina
sample.

4. Elements Detectable By AA are Highlighted in Pink

5. PRINCIPLE:-
•Theabsorptionofenergyabsolutelybygroundstateatomswhile
theyareinthegaseousform.
•CalibrationCurves:AtomicabsorptionshouldfollowBeer’s
lawwithabsorbancebeingdirectlyproportionaltoconcentration.

6. Systematic diagram of AAS

7. Flame
PARTS ARRANGEMENTS OF THE AAS

8. Three Steps are involved in turning a Liquid
Sample into an Atomic gas:--
Nebulization
Desolvation
Volatilization

9. Flame Atomization
There are three types of
particles that exist in the flame:
1)Atoms
2)Ions
3)Molecules

10. INSTRUMENTATION
•RADIATION SOURCE
•CHOPPER
•ATOMIZER
•MONOCHROMATOR
•DETECTOR
•AMPLIFIER
•READOUT DEVICE

11. Hollow Cathode Lamp
CommonRadiationsourceforAtomicAbsorptionSpectrophotometershouldemit
stable,intenseradiationoftheelementtobedetermined,usuallyaresonancelineofthe
element.
Ionizationoftheinertgasoccurswhenapotentialontheorderof300Visapplied
acrosstheelectrodes,whichgeneratesacurrentofabout5to15mA.
Mostofinertgasathighpotential.
Source: Skoog, Holler, and Nieman, Principles of Instrumental Analysis, 5
th
edition, Saunders College Publishing.
Electron and ionic impact on cathode
M(s) M(g)
M(g) M*(g)
M*(g) M(g)

12. Flame Burner
•M
n+
(aq) + anion(aq) salt(s)
•salt(s) salt(g)
•salt(g) atoms (g)
•M*(g) M(g)

13. MONOCHROMATOR
•Neededtochooseoneofseveral
possibleemissionlines(l
emitted)
associatedwithHCT.
•Sincetheyareusually
reasonablywellseparatedfrom
thelineofinterest,itis
straightforwardtousea
monochromatortoeliminatethis
interference.
Chapter 8&9 -13

14. SINGLE BEAM AAS INSTRUMENT
DISADVANTAGE:-
Low stability

15. DOUBLE BEAM AAS INSTRUMENT
ADVANTAGE:-
There is no effect of lamp drift and there is no change in detector sensitivity with time.
Theratiobetweenthereferenceandsamplesignalisthen
amplifiedandfedtothereadout,whichmaybeadigitalmeteror
asignalrecorder.

16. ADVANTAGES OF AAS
•Determinationof68metalsandmetalloidelements.
•Abilitytomakeppbdeterminationsonmajorcomponentsofasample.
•Precisionofmeasurementsbyflamearebetterthan1%rsd.Thereare
fewotherinstrumentalmethodsthatofferthisprecisionsoeasily.
•AAanalysisissubjecttolittleinterference.
•Mostinterferencethatoccurshavebeenwellstudiedanddocumented.
•Samplepreparationissimple.
•Instrumenteasytotuneandoperate.

17. DISADVANTAGES OF AAS
•Limitedtospecificelements
•Requiresskilledoperators
•Interferenceaffectsaccuracy
•Hollowcathodelampsourceisneededforeachelement.
•Expensiveelement.
•Samplepreparationistime-consuming

18. APPLICATION
•AtomicAbsorptionisintheassayofelementsinbiologicalsamples
suchasblood,plasma,otherbodyfluidssuchasurine,saliva,milk&
eveninthemacromolecules.
•AASisamoresensitivetechnique&candetectpresenceofmuchless
quantitiesofelementwiththeexceptionofalkali.
•AAScandetectquantitylessthan1part10
-6
ofmorethantwenty
elements.

19. REFERENCE
Biophysical Chemistry by Upadhyay& UpadhyayNath.3
rd
edition,2004.
Principles of Instrumental Analysis. By Skoog, Holler, and Neiman.
5th edition,1998.
Instrumental Methods of Analysis B. Shivashankar
Instrumental methods of chemical analysis GurdeepR. Chatwal,
Sham K. Anand5th edition.

20. THANK YOU