Flame Atomic Absorption Spectroscopy

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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


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.


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


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


Light absorption

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unexcited ground state atoms, which absorb light at characteristic wavelengths,as shown in the figure.


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.



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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.



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Fuel and oxidant

flame

b Air – acetylene

Air- propane

Air- hydrogen

b Nitrous oxide – acetylene

Auxiliary

oxidant

Fuel


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Common fuels and oxidants used in flame spectroscopy


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The Flame

Calcium Flame Copper Flame Potassium Flame Manganese Flame


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PerkinElmer Analyst 200

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Lamp installation

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Nebulizer

To convert the test solution to gaseous atoms (produce a mist or aerosol)

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Safety Consideration

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Dealing carefully with gas cylinder and air compressor.

Flame Atomic Absorption Spectroscopy

Science

Transcript of Flame Atomic Absorption Spectroscopy