Year 11 Chemistry - Atomic Absorption Spectroscopy

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Chemistry

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11th

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12 Terms

1
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who invented it
alan walsh in 1952
2
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what is it used for
analysis of metal present in solutions as it is highly selective
3
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how does it work
areas of a vaporised metal, within a flame, that are cooler get excited by a hollow cathode lamp and absorb specific wavelengths. the ampunt of light that passes through can be used to identify concentration of the metal.
4
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name all the parts of an AAS machine
hollow cathode lamp, nebuliser, burner, monochromator, detector, sample, fuel and oxiding gas
5
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what does the hollow cathode lamp do
the cathode is composed of the same metal ions that are being analysed in the sample. the lamp can emit different sections of the continuous spectrum, depending on the metal being targeted.
6
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what does the nebuliser do
it sucks up the sample and sprays it into the burner as a fine mist, whilst mixing the fuel and oxidant into the flame.
7
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what does the burner do
the carrier gas takes the sample into the flame, in which the flame atomises the sample by providing it with energy. it provides ground state atoms for absorption and desolvates the analyte. the flame also vaporises analyte into regions of neutral, ionic and molecular species.
8
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where is the HCL aimed
the mostly neutral ground state atoms
9
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what does the monochromator do
it is tuned to a specific wavelength of light, which is being analysed. it “chops” out other wavelengths which may have come from the flame or other sources. it aims to only let the light unabsorbed by the sample through
10
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what does the detector do
it measures how much light the analyte absorbed and can hence tell us the concentration of the metal in the sample. the more light absorbed, the less light detected, and the higher the concentration of the metal. (works oppositley too)
11
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what is a calibration curve
it can show the concentration of an unkown solution based on absorbancy. it is calibrated using known standard solutions with known concentrations.
12
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what is absorbance
the amount of light detected compared to the amount of light emitted by lamp