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1
INSTRUMENTAL ANALYSIS
LAB.
Mr Haydar A.M.S
BSc, MSc
Faculty of Science
Chemistry Department
Email: [email protected]
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Flame Atomic Absorption Spectroscopy
Lab 9
Aim of the experiment
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To be familiar with using flame atomic absorption spectroscopy.
Determination of calcium (Ca) in bottled water.
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Atomic Absorption Spectroscopy
Atomic absorption spectrometry (AAS) is an analytical technique that measures the concentrations of elements.
• Used for qualitative and quantitative detection.
• It’s used for the determination of the presence and concentrations of metals in liquid samples.
• Metals that can be detected include Fe, Cu, Al, Pb, Ca, Zn, Cd and many more.
• Concentrations range is in the low mg/L (ppm) range.
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The AAS instrument
Atomic Absorption Spectroscopy
Flame Atomic Absorption Spectroscopy:
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The technique requires a liquid sample to be aspirated, aerosolized, and mixed with combustible gases, such as acetylene and air or acetylene and nitrous oxide.
The mixture is ignited in a flame whose temperature ranges from 2100 to 2800 ºC.
Atomic Absorption Spectroscopy
Flame Atomic Absorption Spectroscopy:
• When metals are exposed to heat, they absorb light that emit from the source.
• Each metal absorbs light at a characteristic frequency. For example:
Metal Zn Fe Cu Ca Na
λ (nm) 214 248 325 423 589
Atomic Absorption Spectroscopy
1. We set the instrument
at certain wavelength
suitable for a certain
element 2. The element in the
sample will be atomized by
heat
4. The monochromator
isolates the line of
interest
3. The element in the sample
will absorb some of the light,
thus reducing its intensity
5. The detector
measures the change in
intensity
6. A computer data system
converts the change in
intensity into an absorbance
The simple diagram for the AAS
Atomic Absorption Spectroscopy
Light absorption
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unexcited ground state atoms, which absorb light at characteristic wavelengths,as shown in the figure.
Atomic Absorption Spectroscopy
Lamp (Hollow Cathode Lamp)
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Consists of a cathode and an anode. Thecathode is made of the element of interest.The Anode consists of tungsten
1. A large voltage across the anode and cathode willcause the inert gas to ionize.
2. The inert gas ions will then be accelerated intothe cathode, sputtering off atoms from thecathode.
3. Both the inert gas and the sputtered cathodeatoms will in turn be excited by collisions witheach other.
Atomic Absorption Spectroscopy
Lamp (Hollow Cathode Lamp)
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4- When these excited atoms decay to lower energylevels they emit a few spectral lines characteristic ofthe element of interest.
5- The light is emitted directionally through the lamp'swindow, a window made of a glass transparent in theUV and visible wavelengths.
6- The light can then be detected and a spectrum canbe determined.
Atomic Absorption Spectroscopy
Lamp (Hollow Cathode Lamp)
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Atomic Absorption Spectroscopy
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Fuel and oxidant
flame
b Air – acetylene
Air- propane
Air- hydrogen
b Nitrous oxide – acetylene
Auxiliary
oxidant
Fuel
Atomic Absorption Spectroscopy
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Common fuels and oxidants used in flame spectroscopy
Atomic Absorption Spectroscopy
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The Flame
Calcium Flame Copper Flame Potassium Flame Manganese Flame
Atomic Absorption Spectroscopy
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Atomic Absorption Spectroscopy
PerkinElmer Analyst 200
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Atomic Absorption Spectroscopy
Lamp installation
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Atomic Absorption Spectroscopy
Nebulizer
To convert the test solution to gaseous atoms (produce a mist or aerosol)
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Atomic Absorption Spectroscopy
Safety Consideration
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Atomic Absorption Spectroscopy
Safety Consideration
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Atomic Absorption Spectroscopy
Safety Consideration
Dealing carefully with gas cylinder and air compressor.