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Transcript of Atomic spectroscopy
atomic spectroscopy process:
when a solution having a mixture of metallic species is introduced into the flame , the solvent evaporates and metallic vapour is obtained . Some of metal atoms can be raised to an energy level sufficiently high to emit characteristics radiation of metal phenomena used in flame photometry.
The radiant source
For atomic absorption spectroscopy the radiant source is a hollow cathode lamp .
Absorption of a photon results in excitation of an electron from a lower energy level to a higher energy level of atomic orbital .
Thermal or electric energy from an arc, flame, spark or plasma is used to excite an electron from a lower energy level to a higher energy level when excited electrons returns to it's original .
Like atomic absorption, ground state atoms created in a flame are excited by focusing a beam of light into the atomic vapor.the intensity of this fluorescence increases with increasing atom concentration, used for quantitative determination .
This technique incorporate of
both atomic absorption and emission .
Analysing soil, plants and minerals necessary for growth
analysing products for metal and other substance that can have adverse affects such as oil and gas.
Determination of heavy metals in water, soil and air.
In quality control for detecting impurities in drug .
Determination of the dissolution rate of digoxin tablets.
Determination of aluminium in water for injection as a fluorescent complex.
Determination of stability of peptide drugs in solution .
quality assurance and testing for contamination
monitoring potentially hazardous elements in water and wastes output.
The apparatus consists of :
1) Radiant source .
2) Atomizer .
3) Monochromator .
4) Detector .
consists of :
I) cathode :
is made of the element to be determined or coated with it .
2) anode :
is made of Tungsten , Zirconium or Nickle .
3) Pyrex glass :
depending on wavelength of emitted radiation.
4) the lamp
: filled with neon or argon gas
Hollow cathode lamp
burners are used to break the liquids sample into droplets and then allowed to enter into the flame.
the droplets are then evaporated and sample element is then left in residue . the residue is then decomposed by the flame. In this process the sample is reduced into atoms .
how can you determine quantitatively ?
As we know that each element has its own characteristic emission spectrum , hence the intensity of the lines is compared with standard and the concentration can be easily evaluated from the graph .
Advantages of Atomic Absorption Spectroscopy
(1) It does not suffer from spectral interference, which occurs in flame emission spectroscopy.
(2) It is independent of flame temperature.
(3) By atomic absorption technique, traces of one element can easily be determined in presence of high concentration of other elements.
(4) It has proved very successful in the analysis of bronze and copper alloys and in the determination of metals like platinum, gold etc.
(5) More sensitive than AES . A highly specific method of analysis useful in some aspects of quality control .
Disadvantages of Atomic Absorption Spectroscopy
(1) This technique has not proved very successful for the
estimation of elements like V, Si , Mo, Ti and A1
because these elements give oxides in the flame.
(2) In aqueous solution, the anion affects the signal to a
noticeable degree .
(3) Only applicable to metallic elements .
(4) Each element requires a different hallow cathode
lamp for its determination .
is The study of absorption , emission & fluorescence of electromagnetic radiation ( EMR ) by mono atomic particles in gaseous state ( being present in flame ) .
Flame Spectroscopic methods:
The methods of analysis where the concentration of an element in a solution is determined by measuring the absorption , emission & fluorescence of ( EMR ) by mono atomic particles in gaseous state in the flame .
Factors affecting atomic spectroscopy
1- Temperature :
Atomic spectroscopy is temperature dependent since temperature can promote the loss of excitation by collision and bond vibration . A molecule that is not fluorescent at room temperature may become fluorescent at lower temperature .
2- Complex formation :
Formation of a chemical complex with other molecules in sol. can change fluorescence behaviour e.g. the presence of caffeine in solution reduces fluorescence of riboflavin.