Atomic Absorption Spectroscopy

ATOMIC ABSORPTION SPECTROSCOPY

INTRODUCTION

Allan Walsh, in 1955*, was the pioneer for the introduction of atomic absorption spectroscopy (AAS), which eventually proved to be one of the best-known-instrumental-techniques in the analytical armamentarium, that has since been exploited both intensively and extensively in carrying out the quantitative determination of trace metals in liquids of completely diversified nature, for instance : blood serum-for Ca²⁺, Mg²⁺, Na⁺ and K⁺ ; edible oils-Ni²⁺ ; beer samples-Cu⁺ ; gasoline (petrol)-Pb²⁺ ; urine-Se⁴⁺ ; tap-water-Mg²⁺ ; Ca²⁺ ; lubricating oil-Vanadium (V).

The atomic absorption spectroscopy (AAS) may be accomplished either by using a flame-whereby the sample solution is aspirated directly into a flame or by using an electrothermal device-whereby the sample solution is first evaporated and then ignited on a hot surface. It has been noticed that gaseous metal atoms in an unexcited form i.e., ground state atoms, will absorb radiant energy related to their own specific resonance wavelength. Hence, when a light with the same resonance wavelength is passed through a flame comprising of such atoms, a part of the light will be absorbed accordingly. Besides, the degree of absorption would be directly proportional to the total number of ground-state atoms present in the flame, which ultimately forms the basis of Atomic Absorption Spectroscopy (AAS).

AAS facilitates the estimation of a particular element in the presence of many other elements efficaciously. In other words, there is absolutely no necessity to separate the ‘test element’ from the rest thereby not only saving a great deal of time but also eliminating the possibility of various sources of error incurred by these processes. In addition AAS may be used for the estimation of both aqueous and non-aqueous solutions.

Because of the fact that AAS is free from any cumbersome-sample-preparation, it has proved to be an ideal, dependent and versatile analytical tool for the non-chemists specifically, for instance : biologists, clinicians and the engineers, whose interest lies only in the significance of the results.