SELİN CANSU ÖZTÜRK

ŞEYMA ATAKUL

SEZİN GÜNER

ATOMIC ABSORPTION SPECTROMETER

Introduction

Invention

Working Principle of AAS

Instrumentation

Interferences & Correlation Methods

Applications

INVENTION Introduced in 1955 by Alan Walsh in Australia

Firstly used for mining, medical treatment&agriculture

Alan Walsh(1916-1998)

http://www.science.org.au/academy/memoirs/walsh2.html

PROPERTIES OF AAS

The most widely used method in analysis of elements

Based on the absorption of radiation

So sensitive (ppb)

Quantitative analysis

WORKING PRINCIPLE OF AAS Electrons promote to higher orbitals for a short

amount of time by absorbing a energy

M + hv → M*

Relises on Beer-Lambert Law

A= a.b.c

INSTRUMENTATION

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LIGHT SOURCES Hollow Cathode Lamps

Anot-Tungsten wire

Cathode made from the element of interest (Na,K,Ca..)

Argon or neon gas

http://www.safir.be/AAS.ht

LIGHT SOURCES Electrodeless Discharge Lamp

Typically argon gas at low pressure

Narrower line width

Not prefered

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ATOMIZATION

Compounds making up the sample are broken into free atoms.

High temperature is necessary

Basic two types

-Flame atomizer

-Electrothermal atomizer

TYPES OF ATOMIZERS FLAME ATOMIZER

Simplest atomization

Converts analyte into free atoms of vapor phase

Flammable &caustic gases

Not has an inert medium (−)

Short analysis time (−)

TYPES OF ATOMIZERS ELECTROTHERMAL ATOMIZER

A cylindirical graphite tube

Inert gas medium (Argon gas)

Longer anlaysis time than flame

Superior sensitivity, high accuracy

MONOCHROMATOR

Also it is called wavelengh selector

Select the specific wavelenght

Polychromatic light →monochromatic light

Simple one is enough for AAS

DETECTOR

Electromagnetic waves → electric current

The most used one Photomultiplier tube

Have fast response times

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CALIBRATION TECHNIQUES

• Two main techniques

Calibration curve method

Standart addition method

CALIBRATION TECHNIQUES

CALIBRATION CURVE METHOD

Draw a graph

Have two or more variables

-One is set at known values

-One is measured response

Most convenient for a large number of similar samples analysis.

CALIBRATION TECHNIQUES

An example of calibration curve method

CALIBRATION TECHNIQUES STANDART ADDITION METHOD

To measure the analyte concentration in a complex matrix.

Most convenient for small number of samples analysis

Prevent effect of chemical & spectral interferences

INTERFERENCES

Causes higher or lower absorbance value

Two major groups

Chemical Interferences

Spectral Interferences

CHEMICAL INTERFERENCES

The most common one in flame atomizer.

Consequence of chemical reactions.

Reduce amount of oxygen in flame to overcome

SPECTRAL INTERFERENCES

Absorption or emission of the radiation at the same wavelength

Radiation which is absorbed→pozitive errors

Radiation which is emmitted→negative errors

SPECTRAL CORRELATION METHODS

TWO-LINE CORRELATION METHOD

Select two line

characteristic wavelength of analyte

very close to analyte line but not absorbed by analyte

Measure the difference between two lines

SPECTRAL CORRELATION METHODS

CONTINUUM SOURCE CORRELATION METHOD

Select two lamps

Deuterium lamp & hollow cathode lamp

When hollow cathode lamp is used total absorbace is measured

When deuterium lamp is used only background absorption is measured

Measure the difference between two lines.

SPECTRAL CORRELATION METHODS ZEEMAN EFFECT CORRELATION METHOD

Presence of magnetic field.

Splitting of spectral lines.

CONCLUSION

One of the most important technique in quantitative analysis

It is based on the absorption of radiation

Measurements could be done at ppb levels

It’s widely used method

The preparation of the sample is usually simple and rapid

CONCLUSION

There are many adventages

High sensitivity

[10-10 g (flame), 10-14 g (non-flame)]

Good accuracy

(Relative error 0.1 ~ 0.5 % )

High selectivity

APPLICATIONS OF AAS

Water analysis (e.g. Ca, Mg, Fe, Si, Al, Ba content)

Food analysis

Analysis of animal feedstuffs (e.g. Mn, Fe, Cu, Cr, Se,Zn)

Analysis of soils

Clinical analysis (blood samples: whole blood, plasma,serum; Ca, Mg, Li, Na, K, Fe)

REFERENCES

http://www.scribd.com/doc/10513921/Atomic-Absorption-Determination-of-Zinc-and-Copper-in-a-Multivitamin

http://www.hemlin.pp.se/USstarten.html

http://www.learn-english-today.com/business-english/presentations-phrases.htm

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