Atomic absorption spectroscopy pptx

Atomic absorption spectroscopy pptx

1. ATOMIC ABSORPTION SPE C T R O S C O P Y Prepared by :- D.Mahendra,M.Pharm (PA&QA) Asst.Professor-NCOP-T7 Mail:- [email protected]

2. CONTENTS:  Principle of AAS.  Instrumentation.  Applications.

3. INTRODUCTION:  A t o m i c A b s o r p ti o n S p e c t r o s c o p y i s a v e r y co mm o n technique for detectingmetalsand metaloids in samples.  Itis very reliable and simple to use.  Itcan analyze over 62elements.  I t a l s o m ea s u r e s t h e c o n ce n t r a t i o n o f m e t a l s i n t h e sample.

4. HISTORY: The first atomic absorption spectrometer was built by CSIRO scientist Alan Walsh in 1954. Shown in the picture AlanWalsh(left), withaspectrometer.

5. Elements detectable by atomic absorption are highlighted in pink in this periodic table

6. PRINCIPLE:   T h e t e ch n i qu e u s e s b a s i c a l y t h e p ri n c i p l e t h a t f r e e a t o m s ( g a s ) g e ne r a t e d i n a n a t o m i z e r ca n a b s o r b radiation atspecific frequency. Atomic-absorption spectroscopy quantifies the absorption of ground state atoms in thegaseous state.  The atoms absorb ultraviolet or visible light and make transitionstohigher electronicenergy levels. The analyte co n ce n t r a t i o n i s d e t e r m i n e d f r o m t h e a m oun t of absorption.

7. - Concentration measurements are usual y determined from a working curve after calibrating the instrument with standards of known concentration. - A t o m i c a b s o r p t i o n i s a v e r y co mm o n t e c h n i qu e f o r detectingmetalsand metaloids in environmentalsamples .

8. T H E O RY : D etect o r Monochromator Atomizer Nebulizer Hollow Cathode Lamp Atomic Absorption s pe c t r o m ete r

9. Schematicdiagram ofAAS:

10. LIGHT SOURCE:  HolowCathode Lamp are the mostcommonradiation sourceinAAS.  It contains a tungsten anode and a hollow cylindrical cathodemade of the element tobe determined.  These are sealed in a glass tube filled withan inert gas (neon or argon ) .  Each element has its ownunique lamp whichmustbe used for thatanalysis .

11. Quartz window Holow CathodeLamp: Pyrex body c a t h o d e Anode C a t ho de

12. N E B U L I ZE R :  suckup liquid samples atcontroled rate.   createa fine aerosol spray for introduction into flame. M i x t h e ae r o s o l a n d f u e l an d o x i d a n t t ho r ou g h l y for introduction intoflame.

13. Atomizer  Elements tobe analyzed needs tobe in atomicsate.  Atomization is separation of particles into individual molecules and breaking molecules into atoms. This is done by exposing the analyte to high temperatures in a flame or graphitefurnace.

14. ATOMIZERS: ATOMIZER FLAME A T O M I Z E R S GRAPHITE TUBE ATOMIZERS

15. FLAME ATOMIZER :  To createflame, weneed tomixan oxidantgas and a fuel gas.  in mostof thecases air-acetylene flame or nitrous oxide- acetylene flame is used.  liquid or dissolved samples are typicaly used withflame atomizer.

16. GRAPHITE TUBE ATOMIZER :  uses a graphite coatedfurnace tovaporize the sample.  ln GFAAS sample, samples are deposited in a smal graphite coatedtube whichcanthen be heatedto vaporize and atomize the analyte.  The graphite tubes are heatedusing a high current power supply.

17. MONOCHROMATOR:  This is a very importantpart in an AA spectrometer. Itis used toseparate outall of the thousands of lines.   A monochromatoris used toselectthespecific wavelengthof light whichis absorbed by the sample, and toexclude other wavelengths. The selection of the specific light alows the determination of theselected elementin thepresenceof others.

18. D E TE C T O R :  The light selected by the monochromator is directed onto a detector that is typical y a photomultiplier tube , whose function is to convert the light signal into an electrical signalproportional tothelightintensity.  The processing of electrical signal is fulfilled by a signal amplifier . The signal could be displayed for readout , or further fed into a data station for printout by the requested format .

19. Calibration Curve  A calibration curve is used to determine the unknown concentrationof an element in a solution. The instrument is calibrated using several solutions of known concentrations. The absorbance of each known solution is measured and then a calibration curve of concentration vs absorbance is plotted.  The samplesolution is fed into the instrument,and the a b s o r ban c e o f t h e e l e m e n t i n t h i s s o l u t i o n i s measured .The unknownconcentrationof the element is then calculatedfrom the calibrationcurve

20. APPLICATIONS: Determinationof even smal amounts of metals(lead, mercury, calcium, magnesium, etc) as folows:  Environmental studies: drinking water, ocean water,soil.  Food industry.  Pharmaceutical industry.