Slides of Atomicspectroscopy AAS Spectroscopy

Atomic spectroscopy

1. ATOMIC 
SPECTROSCOPY
Dr. FoziaBatool
UNVERSITY OF SARGODHA 

2. ATOMIC SPECTROSCOPY
A
It deals with analysis of atoms. 
A
Our analyte /specie of interest is atom here.
A
Atomic Absorption Spectroscopy (AAS)
A
Atomic Emission Spectroscopy (AES)/ Optical 
Emission Spectroscopy (OES)

4. ATOMIC ABSORPTION 
SPECTROSCOPY
A
1.INTRODUCTION 
A
2.INSTRUMENTATION
A
3.APPLICATIONS

5. INTRODUCTION
A
ATOMIC ABSORPTION SPECTROSCOPY
IS A QUANTITATIVE METHOD OF
ANALYSIS THAT IS APPLICABLE FOR
METALANDSOMENONMETALS

6. HISTORY

8. INTRODUCTION
A
A much larger number of the gaseous metal atoms wil l 
normally remain in the ground state. A
These ground state atoms are capable of absorbing 
radiant energy of their own specific reasonance 
wavelength.
A
If light of the resonance wavelength is passed thro ugh a 
flame containing the atoms then part of the light w ill be 
absorbed.
A
The extend of absorption will be proportional to th e 
number of ground state atoms present in flame.

13. INTRODUCTION
A
Use absorption of light to measure
the
concentrationofgas-phaseatoms
A
Since samples are usually liquied or solids
the
analyte atoms must be vaporized in flame
or
graphitefurnance

14. INTRODUCTION
A
The analyte concentration is determined from 
the absorption of light.
A
It is possible to measure the concentration  of 
absorbing specie by applying the Beer-lambert 
law.

16. SOURCE OF LIGHT
A
Ordinary UV-Visible light source fail in case of 
AAS.
A
Reason is small absorption width of atoms.
A
A special light source was designed for the AAS.
o

17. introduction

18. INSTRUMENTATION
A
LIGHT SOURCE
A
ATOMISATION
A
DETECTION METHODS

19. LIGHT SOURCE.
A
HOLLOW CATHOD LAMP
A
LASERS

20. 1.HOLLOW CATHOD LAMPS
A
HCL.

21. 1.HOLLOW CATHOD LAMP.

22. HCL Construction
A
It consist of an evacuated tube which is filled 
with inert gas.
A
This inert gas may be Aror Ne
A
It contain two electrodes.
A
Cathode is made by using metal which we are 
going to analyze.
A
Anode is made by any inert element.
A
On one side quartz window is present 

24. Working

25. Working
A
When HCI is connected with electricity inert gas 
got ionized.
A
Ar change to Ar+ and electron
A
These Arions moves toward cathode with high 
speed
A
As soon as these ions strike cathode, they 
physically dislodged metal atoms from cathode.
A
This process of metal dislodging is called 
sputtering.

26. WORKING
A
These metal atoms got excited also due to 
energy of inert gas when it strike with metal 
atoms.
A
These excited atoms when de-excite they emit 
specific light of that element.
A
This light is used as a source of excitation for 
metals.
A
Sodium absorb 589 nm light only. 

27. HCL a Specific Light Source
A
For every metal we need a separate HCL lamp
A
As every metal emit specific light and also 
absorb a particular wave length.

28. LASERS

29. LIGHT SOURCE.
A
Hollow Cathode lamps can be used to detect 
one or several atomic specie simultaneously
A
While lasers are more sensitive have a 
disadvantage to detect one Element at a time.

30. 1.HOLLOW CATHOD LAMPS
A
HOLLOW CATHOD LAMPS ARE TYPE OF 
DISCHARGE LAMP THAT PRODUCED 
NARROW EMISSION FROM ATOMIC 
SPECIE.
A
THEY GET THEIR NAME FOR CUP-
SHAPED CATHOD WHICH IS MADE 
FROM THE ELEMENT OF INTERST.

31. ATOMISATION
A
ATOMIC ABSORPTION SPECTROSCOPY 
REQUIRES THAT ANALYTE ATOM MUST 
BE IN GAS PHASE.
A
Sample is converted into gaseous free atomic 
form by different ways

32. Types of AAS on the Basis of 
Atomizer A
Flame AAS
A
Graphite Furnace AAS
A
Cold Vapor AAS
A
Hydride Generation AAS

33. FLAMES 
A
FLAME AAS CAN ONLY ANALYSE 
SOLUTIONS
A
A BURNER IS USED TO INCREASE THE 
ABSORPTION PATH LENGTH
A
SOLUTION ARE ASPIRATED WITH GAS 
FLOW INTO MIXING CHAMBER TO 
FORM SMALL DROPLETS TO ENTRING 
THE FLAME.

34. Burners
A
Total Consumption Burner
A
Premix Burner

35. Total Consumption Burner
A
Intotal-consumptionburner,thefuelandoxidant
(support)gasesaremixedandcombustatthetip
of the burner. The fuel (usually acetylene),
oxidant (usually air) and sample all meet at the
base of flame. The sample is drawn up into the
flamebythe‘VenturiEffect’,bythesupportgas.
The gas creates a partial vacuum above the
capillarybarrel,causingthe sampletobeforced
upthecapillary.

36. Total Consumption Burner
A
Itisbrokenintoafinesprayatthetipwhere
the gases are turbulently mixed and burned.
Thisistheusualprocessof‘nebulisation’.
A
Theburneriscalledtotalconsumptionbecause
theentireaspiratedsampleenterstheflameor
inotherwordsthesamplesolutionisdirectly
aspirated into the flame. All desolvation,
atomization, and excitation occurs in the
flame.

37. Total Consumption Burner

38. Premix Chamber Burner
A
The second type of burner, most commonly
used now, is the premix chamber burner,
sometimescalledlaminar-flowchamber.Premix
burnerswerethefirstpurpose-designedburners,
andtheycanbetracedbackmorethan100years
totheBunsenandsimilarlaboratoryburners.

39. Premix Chamber Burner
Construction
A
It consist of three parts
A
1. Nebulization Assembly
A
2. Premix Chamber
A
3. Long Burner Head

40. Nebulization Assembly
A
It convert sample into small mist drops by 
pressure of fuel.

41. Premix Chamber
A
The fuel and support gases are mixed in a
chamber before they enter the burner head
(through a slot) where they combust. The
sample solution is again aspirated through a
capillarybythe‘Venturieffect’usingthesupport
gas for the aspiration. Large droplets of the
samplecondenseanddrainoutofthechamber.

42. Premix Chamber
A
Theremainingfinedropletsmixwiththegases
and enter the flame. As much as 90% of the
droplets condense out, leaving only 10% to
enter the flame. The 90% of the sample that
does not reach the flame will travels back
through the mixing chamber and out as waste
drain.

43. Burner Head
A
Long burner head for flame burning is available. 

44. FLAME ATOMISATION

45. FLAME ATOMISATION

46. STEPS IN ATOMIZATION

47. FLAME ATOMISATION

48. WAVELENGTH SELECTION 
DEVICE
A
Grating

49. DETECTOR

50. Electro thermal AAS
Graphite Furnace AAS

51. FURNANCE 
A
IMPROVED SENSITIVITY OVER FLAME
SOURCES
A
LESSSAMPLEISREQUIRED
A
GENERALLY SAME TEMPERATURE
RANGEASFLAMES
A
MORE DIFICULAT TO USE BUT WITH
OPERATOR SKILL AT ATOMISATION
STEP PRECISE MEASUREMENT CAN
MADE

52. GRAPHITE FURNACE

53. CONSTRUCTION OF GF

54. CONSTRUCTION
A
It consist of graphite rode which is heated by 
electric energy.
A
Purge Gas: Argon is used as purge gas in 
GFAAS to remove impurities and air from 
furnace surface. As air can oxidize the furnace 
surface.
A
Cool water is circulated to make furnace cool 
after one sample analysis. 

55. CONSTRUCTION

60. COLD VAPOR AAS
A
This method of atomization is limited for Hg 
only, as Hg is only metal present in liquid form 
at room temperature.
A
Hg is atomized by chemical reaction without 
heating so it is called cold vapor AAS. 

61. Sn
+2
--------------- Sn
+4
2Hg+------------------ Hg
Gaseous Mercury goes to long path length cell.

64. HYDRIDE GENERATION AAS A
This technique is used for those metals which 
form volatile hydrides e.gAs, Sb.
A
Mostly used for Arsenic analysis.
A
Sample is chemically reacted with NaBH
4to 
convert As into AsH
3
A
This hydride is volatile in nature 
A
AsH
3 is called Arsine gas.

65. DETECTION METHODS

66. PHOTOMUTIPLIER TUBE.PMT
A
USEFUL IN LOW INTESTIES
APPLICATIONS
A
FEW ELECTRON STRIKE THE
PHOTOCATOHD
A
ELECTRON EMITED AND AMPLIFIED
BYDYNODESCHAIN
A
MANYELECTRONSTRICKTHEANODE

69. APPLICATIONS
A
Analytical chemistry
A
Quantitative Determination of Metallic 
Impurities in Pure Uranium Compounds
A
Remote sensing
A
Astronomy