Modern Pharmaceutical Analytical Techniques

1. ATOMIC
ABSORPTION
SPECTROSCOPY
PRESENTEDBY:
PundSurajBabanrao
M.Pharm1stYear.(Pharmaceutics)
RAJGAD DNYANPEETH COLLEGE
OF PHARMACY, BHOR, PUNE.

2. CONTENTS:
 Principleof AAS.
 Instrumentation.
 Applications.
 Experiments.

3. INTRODUCTION:
 Atomic Absorption Spectroscopy is a very common
techniquefordetectingmetalsandmetalloidsin samples.
 Itisveryreliableandsimpletouse.
 Itcananalyzeover62elements.
 It also measures the concentration of metals in the
sample.

4. HISTORY:
The first atomic absorption spectrometer was built by
CSIRO scientistAlanWalshin1954.Showninthe picture
AlanWalsh(left),withaspectrometer.

5. Elementsdetectablebyatomicabsorptionarehighlightedinpinkinthis
periodic table

6. PRINCIPLE:


The technique uses basically the principle that free
atoms (gas) generated in an atomizer can absorb
radiationatspecificfrequency.
Atomic-absorptionspectroscopyquantifiesthe
absorptionofgroundstateatomsinthegaseousstate.
 Theatomsabsorbultravioletorvisiblelightandmake
transitionstohigherelectronicenergylevels.The analyte
concentration is determined from the amount
of absorption.

7. - Concentration measurements are usually determined from a
working curve after calibrating the instrument withstandards
ofknown concentration.
- Atomic absorption is a very common technique for
detectingmetalsandmetalloidsinenvironmentalsamples.

8. THEORY:
Detector
Monochromator Atomizer
Nebulizer
Hollow Cathode
Lamp
Atomic
Absorption
spectrometer

10. SchematicdiagramofAAS:

11. LIGHT SOURCE:




HollowCathodeLamparethemostcommonradiation
sourceinAAS.
It contains a tungsten anode and a hollow cylindrical
cathodemadeoftheelementtobe determined.
Thesearesealedinaglasstubefilledwithaninertgas
(neonorargon) .
Eachelementhasitsownuniquelampwhichmustbe used
forthatanalysis .

12. Quartz window
HollowCathodeLamp:
Pyrex body
cathode
Anode
Cathode

13. NEBULIZER:
 suckupliquidsamplesatcontrolledrate.


createafineaerosolsprayforintroductioninto flame.
Mix the aerosol and fuel and oxidant thoroughly
forintroductionintoflame.

14. Atomizer
 Elements tobeanalyzedneedstobeinatomicsate.
 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
flameorgraphitefurnace.

15. ATOMIZERS:
ATOMIZER
FLAME
ATOMIZERS
GRAPHITE TUBE
ATOMIZERS

16. FLAME ATOMIZER:
 Tocreateflame,weneedtomixanoxidantgasanda fuel
gas.
 inmostof thecasesair-acetyleneflameornitrousoxide-
acetyleneflameis used.
 liquidordissolvedsamplesaretypicallyusedwithflame
atomizer.

18. GRAPHITE TUBE ATOMIZER:
 usesagraphitecoatedfurnacetovaporizethe sample.
 lnGFAAS sample,samplesaredepositedinasmall
graphite coatedtubewhichcanthenbeheatedto
vaporizeandatomizetheanalyte.
 Thegraphitetubesareheatedusingahighcurrent
power supply.

19. MONOCHROMATOR:
 ThisisaveryimportantpartinanAAspectrometer.Itis
usedtoseparateoutallof thethousandsoflines.


Amonochromatorisusedtoselectthespecific
wavelengthof lightwhichisabsorbedbythesample,and
toexcludeotherwavelengths.
Theselectionof thespecificlightallowsthe determination
of theselectedelementinthepresenceof others.

20. DETECTOR:
 The light selected by the monochromator is directed onto
a detector that is typically a photomultiplier tube , whose
function is to convert the light signal into an electrical
signalproportionaltothelightintensity.
 The processing of electrical signal is fulfilled by a signal
amplifier . The signal could be displayed for readout , or
furtherfedintoadatastationforprintoutbythe requested
format.

21. Calibration Curve
 A calibration curve is used to determine the unknown
concentrationof anelementinasolution.The instrument
is calibrated using several solutions of known
concentrations. The absorbance of each known solution
ismeasuredandthenacalibrationcurveof concentration
vsabsorbanceis plotted.
 Thesamplesolutionisfedintotheinstrument,and the
absorbance of the element in this solution is
measured.Theunknownconcentrationof theelementis
thencalculatedfromthecalibrationcurve

22. APPLICATIONS:
Determinationof evensmallamountsof metals(lead,
mercury,calcium,magnesium,etc)as follows:
 Environmentalstudies:drinkingwater,oceanwater,soil.
 Foodindustry.
 Pharmaceuticalindustry.

23. REFERENCES:



Vogel’s Textbook of Quantitative Analysis, G. Svehla,
Pearson.
Principles of Instrumental Analysis, Skoog.
Basic Concepts Of Analytical chemistry, S M Khopkar.