- Atomic absorption spectroscopy is a technique used to quantitatively determine trace metals in liquids. It works by vaporizing the liquid sample and measuring the absorption of light from hollow cathode lamps by atoms of the metal in the vapor. - The amount of light absorbed is directly proportional to the number of metal atoms in the vapor. By measuring the absorption, the concentration of the metal in the original sample can be determined. - Atomic absorption spectroscopy has detection limits in the parts-per-million or parts-per-billion range for many metals. It is a specific technique as each metal absorbs only its own characteristic wavelength.

1. - BY
SUBHASISH DAS
M.PHARM 1ST YEAR
ROLL- 19320712001
REG. NO-121932310012 OF 2012-2013
CLASS ROLL – 13 .

2. INTRODUCTION
 Atomic absorption spectroscopy was introduced in mid 1950’s by
“Alan Walsh”.
 Most powerful technique to determine trace metals in liquid
quantitatively
 In a sentence “Atomic Absorption Spectroscopy (AAS) “ is a method
of elemental analysis , particularly useful for determination of trace
metals in liquid and is almost independent of the molecular form of
the metal in sample.

3. MERITS
 The atomic absorption technique is specific
because the atoms of a particular element can only
absorb radiation of their own characteristic
wavelength
 Some element possess higher detection limits by
atomic absorption like Ag , As , Au etc.
 Independent of flame temperature.

4. THEORY
 Atomic absorption spectroscopy deals with
absorption of specific wave length of radiation by
neutral atoms in the ground state.
 When a light of this wavelength is allowed to pass
through a flame having atoms of the metallic
species , part of the light will be proportional to the
density of the atoms in the flame.

5. EQUATIONS
 At ,
υ the total amount of light absorbed = ( e2/mc)*Nf
Where,
e = charge on electron.
m = mass of electron.
c = speed of light.
N = total number of atoms that can absorb frequency
ν in the light path.
f = the oscillator strength or ability for each atom to
absorb at frequency ν.
contd..

6. Contd..
As ,e, m, c are constant equation becomes
Total amount of light absorbed = constant * N * f

7. GROTRIAN DIAGRAMME
 Walter Robert Wilhelm Grotrian (21/4/1890 - 3/3/ 1954)
was a German astronomer and astrophysicist.
 Grotrian studied the emission line from the solar corona in
the green region of the spectrum; this emission line could not
be attributed to any known chemical element and was
thought to be a new element (which scientists named
"coronium").
 Grotrian and Bengt Edlén from Sweden demonstrated that the
two observed emission lines arise from iron atoms that have
lost about half their 26 electrons .

8. ATOMIC ABSORPTION TRANSITIONS

9. EFFECT OF FLAME
TEMPERATURE
e
g
g
=
N
N E
o
u
o
u ex
kT


•Effect of flame temperature: Since flame is at high temperature
might have an effect on fraction of atoms in excited state.
•Boltzmann's equation describes effect of flame temperature:
where

10. e
g
g
=
N
N
kT
E
o
u
o
u ex

Where,
Nu is the number of atoms in excited state
gu the number of degenerated orbitals on this energy level.
No and go refers to the same figures at ground state.
k is Boltzmann constant and
T is the temperature .
E is energy difference between two orbitals
Therefore, an increase in temperature results in an increase of the
number of excited atoms, which is equivalent to a lowering in
absorption

11. PRINCIPLE
Light source Light Light
DETECTOR
Gaseous
molecules
Solid/Gas
aerosol
Spray
S
I
G
N
A
L
RECORDER

12. A light beam is passed through the flame,
Radiation is absorbed, transforming the ground
state atoms to an exited state.

13. WORKING PRINCIPLE
 Liquid sample → formation of droplet → fine
residue
↓
neutral atom ← Formation of neutral atom
absorbs specific
Wavelength of radiation from hollow cathode lamp.
↓
Measurement of intensity of radiation absorbed by using
photometric detectors.

14. Atomic Absorption
Instrumentations

15. INSTRUMENTATION
SINGLE BEAM DOUBLE BEAM

16. MAJOR PARTS OF
INSTRUMENT
 HOLLOW CATHODE LAMP - The cathode is made up of specific element
or alloys of elements or coating of elements on cathode , as current is
applied between anode & cathode , metal atoms emerge from hollow cup
and collides with filler glass . Due to the collision, number of metal atoms are
excited and emit their characteristic radiation , this is absorbed by neutral
atoms of same element in ground state , occur in the flame , when sample
solution is sprayed. Band width-0.001to 0.01 nm.

17. CONTD…
 ATOMISER ASSEMBLY–
Assembly used as atomizer and nebulizer.
Premix type Total consumption Graphite furnace

18. INTERFERENCES
A. PHYSICAL – Due to sample matrix or flame or scattering or similar
alkali halides , termed as Background absorption.
remedy- use background corrector

19. CONTD..
B. CHEMICAL – In complete dissociation of
compound ,
remedy – 1. use high temperature flame
2. chemical means are applied.
C. IONISATION – Due to too high flame temperature.
remedy – addition of more easily ionisable
element.
D. SCATTERING EFFECTS – Due to presence of
high concentration of interfering element.
remedy – using a continuum source.

20. APPLICATIONS
 Estimation of trace elements in biological fluid.
 Estimation of Copper ,Zinc, Nickel in food products.
 Estimation of Zinc in Zinc insulin injection
 Estimation of lead in Calcium Carbonate, petrol.
 Estimation of elements in soil ,water, effluents,
ceramic etc.
ELEMENT Λ (nm) ppm
SODIUM 589 0.01
POTASSIUM 766.5 0.01
CALCIUM 442.7 0.05
LEAD 217 0.01

21. DETECTION LIMIT AND
SENSITIVITY
 The concentration of element present in the sample solution
which produces 1% absorption.
 Sensitivity , expressed in terms of μg/ml for 1% absorption.
 C1%=(C0.1*0.0044)/0.1
Where,
C1% = the concentration give rise to 1% absorption.
C0.1 = the concentration give rise to an absorbance of 0.1

22. DEMERITS
 A separate lamp for each element to be determined
is required.
 Elements produce oxides in flame may not be
successfully determined quantitatively.
 In aqueous solution , the predominant anions
affects the signal to a negotiable degree.

23. CONCLUSION
 ATOMIC ABSORPTION SPECTROSCOPY mainly
used to determine trace element in soil samples,
waters, petrol etc ; not just qualitatively, mainly
quantitative determination of metals are done .
 In case of isolation and purification of herbal drugs
or phytochemical form crude form AAS helps as a
support to determine the amount of trace material
present , so as an analytical tool it is very use full.

24. REFERENCES
1. G. R. Chatwal , S. K. Anand (2010) , Instrumental Methods Of
Chemical Analysis , Himalaya Publishing house , Ch – 13 , Pg. no. -
2.340 – 2.366 .
2 . A. H. Beckett , J. B. Stenlake , (2007) , Practical Pharmaceutical
Chemistry , CBS Publishers & Distributors Pvt. Ltd. , 4th ed. , part two,
Ch – 8 , Pg. no .- 346 – 357. CBS Pubs ISBN : 81-239-0514-9 ,
Athlone ISBN : 0-485-11323-8
3. Hobart H. Williard , Lynne L . Merritt, jr. , John A. Dean , Frank A.
Settle, jr. , Instrumental Methods Of Analysis , (2006), CBS Publishers
& Distributors Pvt. Ltd. , 7th ed. , Ch – 9 , Pg no – 243- 255 , ISBN :
81-239-0943-8