SELİN CANSU ÖZTÜRK ŞEYMA ATAKUL SEZİN...
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Transcript of SELİN CANSU ÖZTÜRK ŞEYMA ATAKUL SEZİN...
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
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
www.freepatentsonline.com
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
www.answers.com
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 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