AAS (spektroskopi serapan atom/ Atomic absorption spectroscopy) pertama kali dimanfaatkan Alan Walsh (1955). metode ini sangat tepat untuk analisis zat berkonsentrasi rendah. metode AAS berprinsip padaabsorpsi cahaya oleh atom-atom. Atom menyerap cahaya tersebut pada panjang gelombang tertentu, tergantung sifat unsurnya. Unsur-unsur yang dapat dideteksi oleh AAS/SSA adalah unsur-unsur logam, dan beberapa unsur non-logam (3 unsur).

1. First Group
A. Khaerunnisa Ha
rdya
nti Arki
Nur Hasanah Jusm
an
Nurhikmah
Atomic
Absorption
Spectrometry
ICP CHEMISTRY A 2011
(AAS)
FMIPA UNM
2013
Sarce Siruru
Hasra Jalil

2. Contents
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•
•
•
•
What is AAS
Theory
Instrumentations
Principle of AAS
Applications

3. What is AAS ?
Atomic absorption spectroscopy is a quantitative
method of analysis that is applicable to many metals
and a few nonmetals.
The technique was introduced in 1955 by Walsh
in Australia (A.Walsh, Spectrochim. Acta, 1955,
7, 108)
The application of
atomic absorption
spectra to chemical
analysis
Concentrations range is
in the low mg/L (ppm)
range.

4. Theory
A much larger number of the gaseous metal atoms
will normally remain in the ground state.
These ground state atoms are capable of absorbing
radiant energy of their own specific resonance
wavelength.
If light of the resonance wavelength is passed through a
flame containing the atoms in question, then part of the
light will be absorbed.
The extend of absorption will be proportional to the
number of ground state atoms present in the flame.

5. the gaseous metal atoms
specific resonance wavelength
extend of absorption
the extend of absorption vs the number of ground state atoms
present in the flame.

6. AAS Instrument

7. The simple diagram for the AAS
4. T element in the sample
he
will absorb some of the light,
thus reducing its intensity
5. T monochromator
he
isolates the line of
interest
3. A beam of UV light
will be focused on the
sample
1. W set the
e
instrument at certain
wavelength suitable
for a certain element
2. T element
he
in the sample
will be atomized
by heat
6. T detector
he
measures the change
in intensity
7. A computer data system
converts the change in
intensity into an
absorbance

8. Flame atomization
Processes occurring during atomization

9. Nebuliser - burner
To convert the test solution to gaseous atoms
Nebuliser --- to produce a mist or aerosol of the
test solution
Vaporising chamber --Fine mist is mixed with the fuel gas and the carrier gas
Larger droplets of liquid fall out from the gas stream and
discharged to waste
Burner head --- The flame path is about 10 –12 cm

10. 1. Nebulizer:
4. T mixture flows
he
immediately into the burner
head.
5. It burns as a smooth,
laminar flame evenly
distributed along a narrow
slot.
1. mixes acetylene (the fuel)
and oxidant
(air or nitrous oxide).
6. L
iquid sample not flowing
into the flame collects in the
waste.
3. T result is a heterogeneous
he
mixture of gases (fuel + oxidant) and
suspended aerosol (finely dispersed
sample).
2. A negative pressure is formed at
the end of the small diameter,
plastic nebulizer tube→
(aspiration).
Note:
W
hen do we use NO2 ?

11. Elements that are highlighted in pink
are detectable by AAS

12. Principle of Atomic Absorption
Spectrophotometer
Atomized elements each absorb energy of
a wavelength that is peculiar to that
element. The atomic absorption method
uses as its light source a hollow cathode
lamp which emits light of a wavelength that
is peculiar to each element. Elements
within a solution are heated in a flame or
electrically (2000K to 3000K) and
subsequently determined using the fact
that the degree of absorption will vary with
its concentration.
Light absorption
process of atoms

13. Principle of Atomic Absorption
Spectrophotometer
Atomic Absorption Spectroscopy, AAS
Excited state E1
Absorption
Ground state E0
Atomic Emission Spectroscopy, AES
Excited state E1
e
e
Emission
Ground state E0
e

14. Characters of the atomic absorption spectrum
Profile of the absorption line
K0 - maximal absorption
coefficient
Δ ν - half width
ν 0 - central wavelength

15. The relationship between absorbance
and the concentration of atoms
Beer’s law
I t = I 0ν e
-Kνl
A = log （ I 0ν / I t ） = 0.4343 K ν l
I t - intensity of the transmitted light
I o – intensity of the incident light signal
l – the path length through the flame (cm)

16. Types of Pretreatment
Dilution
Dilute the sample with purified water, dilute acid, or organic solvents.
Examples: food products (e.g., dairy products), pharmaceuticals, and biological
samples (e.g., blood, urine).
Dry Decomposition
Heat the sample to a high temperature (400 to 500°C), Decomposition is possible
in a short time (a few hours) and operation is simple.
Elements with low boiling points (e.g., Hg, As, Se, Te, and Sb) will vaporize
Wet Decomposition
Heat the sample together with acid to a low temperature (approx. 300°C). Suitable for
volatile elements.
A long time is required for the decomposition of organic substances.
Microwave Decomposition
Decompose the sample at high pressure by heating it together with acid to a
temperature in the range 100 to 200°C in a sealed Teflon container.
The decomposition process is sealed; there is little vaporization of elements with low
boiling points; the decomposition time is short; there is little contamination from the
operating environment and the reagent; and only a small amount of acid is required.
Examples: Sediment, soil, dust, ceramics, living organisms, food products, etc.

17. Characters of the atomic absorption spectrum
Natural broadening
determined by the lifetime of the excited state
and Heisenberg’s uncertainty principle （ 10-5 nm ）
Doppler Broadening
（ 10-3 nm ）
results from the rapid motion of atoms as they emit
or absorb radiation
Collisional Broadening
collisions between atoms and molecules in the gas phase
lead to deactivation of the excited state and thus broadening
the spectral lines

18. Characters of the atomic absorption spectrum
Doppler Broadening
（ 10-3 nm ）
results from the rapid motion of atoms as they emit
or absorb radiation

19. Application of AAS
AAS
Pretreatment (dissolution) is required for solid samples.

20. Results of Quantitative
Analysis of Cd in Rice
The following 2 methods can be used to analyze unpolished and polished rice decomposed using
acid:
Flame method
Furnace method
Polished rice:
0.118 ppm
0.1 ppm
0.5 ppm
Unpolished rice:
0.070 ppm
Polished rice :
0.118 ppm
Unpolished rice :
0.073 ppm
Air-C2H2
Injected amount: 10 µL
Interference inhibitor: Pd 50ppm 5 µL
Ashing: 400°C; Atomization: 1,800°C

21. AAS Interferences

22. AAS Advantages and
Disadvantages'
Advantages
1. High selectivity and sensitivity
2. Fast and simple working
3. Doesn’t need metals separation
Disadvantages
1. Analysis doesn’t simultaneous
2. Fragment have to form ready measure solution
3. Limit types of cathode lamp (expensives)

23. THANK YOU 

24. Questions
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How could atom’s collision
Sample preparation of AAS
The type of sample liquid or gas
Function of AAS of few nonmetals
examples
• What happen to the sample in flame