Atomic absorption spectrometry
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Determination of the exchanged Fe-ions

The atomic absorption spectrometry (AAS) is an analytical method based on the absorption of UV or visible light by gaseous atoms. The sample becomes atomized by injecting a solution into a flame (flame AAS) or by heating a dried sample in an energized graphite pipe (graphite tube AAS). As source of light, a hollow-cathode lamp (HCL) is used to determine the contained element. These element’s atoms in the flame absorb precisely the wavelength sent by the source of light. The absorption is proportional to the concentration. The light produced by the HCL is spectrally divided in the monochromator, and only the resonance line is passed trough the exit slit.

The concentration value in the AAS is based on the Lambert-Beer law:

with :

Determination of the exchanged Fe-ions in the filtrate (1) with AAS

Materials

Determination of Fe

Interferences (disturbances)

The Fe signal can be reduced by silicates. This disturbance can be minimized by an addition of a 0.2% CaCl2 solution.

Execution

Prepare 100 mL of stock solution II with a concentration of 100 mg Fe/L.

Preparation of the Fe calibration solutions

Prepare the matrix solutions with following concentrations in 100 mL measuring flask.

Fe concentration
Blank value 0 mg/L Fe
Calibration solution 1 2,0 mg/L Fe
Calibration solution 2 5,0 mg/L Fe

Add 1 mL of 20% CaCl2 solution to every standard.

Determination of Fe concentration in the filtrate (1)