Origin of an Atomic Absorption Peak E2E2 E1E1  E = h Frequency Intensity Energy Transition Absorption Spectrum 1

Atomic Absorption for a Hydrogen Atom Electronic energy levels in a H atom 1s 2s 2p 3s 3p 3d The lowest energy state has the single electron in the 1s orbital 1s 1 2

A brief history of Atomic Absorption Spectrometry 1802 Wollastone - discovered black lines in Sun's spectrum which were subsequently investigated by Fraunhoffer (1823). Solar spectrum 3

A brief history of Atomic Absorption Spectrometry – 1820 Brewster - suggested black lines in solar spectrum due to absorption processes in Sun's atmosphere. – 1859 Kirchhoff and Bunsen - demonstrated Na D line absorption in visible spectra. 4

A brief history of AAS Hydrogen spectrum Solar spectrum Mercury spectrum Interpretation of Fraunhoffer lines in terms of atomic absorption by elements in the suns atmosphere Astronomers use atomic absorption to estimate metal concentrations in atmospheres of stars. 5

What is AAS? ( AAS) Atomic Absorption Spectroscopy is: Quantitative technique Typical samples: low viscosity samples Generally uses to determine the amount of several metals (e.g. Cu, Fe, Zn, Mg) in the soil, blood, air, water, and food. Occasionally can be use as a qualitative technique (can indentify chemicals that are present) – 68 elements

In the electromagnetic spectrum, it uses the visible part to detect the presence of metals. Foundation of the technique: the absorption of the light energy that has the right wavelength causes the electrons from the sample to be promoted from a lower energy level to a higher energy level.