atomic absorption spectroscopy

1. BASIC PRINCIPLE AND APPLICATION
OF ATOMIC ABSORPTION
SPECTROSCOPY

2. ATOMIC ABSORPTION SPECTROSCOPY

3. INTRODUCTION
 ATOMIC ABSORPTION SPECTROSCOPY IS AN ABSORPTION SPECTROSCOPIC
METHOD WHERE RADIATION FROM A SOURCE IS ABSORBED BY NON-EXCITED
ATOMS IN THE VAPOR STATE.
 ATOMIC ABSORPTION SPECTROSCOPY DEALS WITH THE ABSORPTION OF
SPECIFIC WAVELENGTH RADIATION BY NEUTRAL ATOMS IN THE GROUND STATE.

4. PRINCIPLE OF ATOMIC ABSORPTION SPECTROSCOPY
Liquid sample
Formation of droplets
Fine residue
Formation of Neutral atoms
flame

5. Neutral atoms absorb specific wavelength of
radiation from hollow cathode lamp
Measurement of intensity of radiation absorbed by the
neutral atoms using a detector.

7. INSTRUMENTATION
Sharp-line radiation source (usually a hollow-cathode
lamp)
 A solution nebulizer and burner (an electrically heated
furnace)
Monochromator
 Photomultiplier and
Recording system

8. HOLLOW CATHODE LAMP
When a current flows between the anode and cathode in this lamps, metal atoms
are sputtered from the cathode cup, and collisions occur with the filler gas. A
number of metal atoms become excited and give off their characteristic radiation.

9. BURNER WITH FUELAND OXIDANT ( NEBULIZER )
 The burner consists of a metal block containing a row of
circular holes or one or more slots about 10 cm long.
 The most generally useful flame is air-acetylene,
 The cooler air-propanea and the
Hotter nitrous oxide-acetylene flames are also used.

10. FLAMELESS VAPORIZATION TECHNIQUES
Electro thermal Atomizers
 Cold Vapor Systems
 Hydride generation systems

11. ELECTRO THERMALATOMIZERS

12. COLD VAPOR SYSTEMS
• Mercury is a unique metal in that it has a significant vapor pressure at room
temperature. Furthermore, the vapor is monatomic and unreactive. Thus it may
be entrained in a gas stream and measured by the atomic absorption of this
cold vapor.
• A typical analytical method first involve the use of an oxidizing mixture such
as sulphuric acid and potassium permanganate to destroy organic matter.

13. HYDRIDE GENERATION SYSTEMS
A number of elements such as arsenic, tellurium and selenium may be reduced by
a suitable reagent, e.g. sodium borohydride in acidic solution, to their hydrides as
follows..
6BH4 + As 3+ + 3H = 3B2 H6 + 3H2 + AsH3

14. ADVANTAGES OF AAS
 Solutions, slurries and solid samples can be analyzed.
 Much more efficient atomization
Greater sensitivity
 Smaller quantities of sample (typically 5 – 50 μL)
Provides a reducing environment for easily oxidized.

15. DISADVANTAGES
 Expensive
Low precision
 Low sample throughput
Requires high level of operator skill
 Sample must be in solution or at least volatile
Individual source lamps required foreach element.