Atomic absorption spectroscopy (AAS) involves converting liquid samples into atomic vapor and measuring their absorption of radiation at characteristic wavelengths. The amount of light absorbed is directly related to the concentration of the absorbing element. AAS instrumentation consists of a hollow cathode lamp radiation source, flame atomizer, monochromator, detector, and recorder. It can quantitatively determine elements at the ppm and ppb levels in aqueous and non-aqueous solutions. AAS is widely used in fields like analytical chemistry, environmental analysis, and food testing.