Atomic Absorption Spectroscopy. Qualitative test for metals in solution Can also be used for…
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Atomic Absorption Spectroscopy
Qualitative test for metals in solution
Can also be used for coloured lights This emission of light is called an
emission spectrum
Flame Test
Electrons exist in finite energy levels,eg 1s2 2s2 2p6 3s1
This is the ground state for sodium When an electron receives energy it absorbs
only that amount of energy to raise it to a higher available energy level
The atom is now energetically unstable and will lose this excess energy in the form of electromagnetic radiation
Emission Spectrum
Involves the absorption of electromagnetic radiation of certain wavelengths
A spectrophotometer measures the intensity of the radiation transmitted through the sample relative to the intensity entering
Can therefore be used for quantitative measurements
AAS
AAS
Cathode lamp containing the metal to be analysed
Emits radiation of certain frequencies that correspond to the energy gaps characteristic of the metal sample
This means that impurities will not interfere with the measurements
AAS – radiation source
The radiation is directed through a flame into which the sample is sprayed.
Any metal atoms the same as the lamp will absorb the radiation emitted
The absorbance is proportional to the concentration of metal in the sample
AAS - flame
A filter or monochromator is used to select the frequency of light to pass through to the detector
Allows AAS to be used with impure samples
AAS – filter and detector
Concentration Absorbance2.0 0.0514.0 0.0976.0 0.1488.0 0.20110.0 0.253
Example
1 2 3 4 5 6 7 8 90
0.05
0.1
0.15
0.2
0.25
Concentration ppm
Abso
rban
ceCalibration Curve