The concentration of cadmium in an unknown sample was determined using flame AAS

Question

The concentration of cadmium in an unknown sample was determined using flame AAS. A calibration curve was generated by measuring the signals of a set of standard solutions. The unknown sample has a measured absorbance of A = 1.437 which yielded a concentration of [Cd] = 12.71 ppm based on the calibration curve. A second experimental technique was used to determine cadmium, and it resulted in an accurate value for cadmium of [Cd] = 16.28 ppm. Explain why the cadmium concentration determined by AAS was in error.

Explanation / Answer

The AAS (Atomic absorption technique) measures the amount of energy in the form of light emitted with the photons.

The problem with the method of Cadmium calculation is that the air will slowly oxidize the Cadmium present into Cadmium oxide, leading to less number of photons emitted by the Cadmium which will lead to wrong interpretation in the calculation of photons and hence lesser concentration

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