Atomic Absorption Spectroscopy Learning Module

Atomic Absorption Spectroscopy requires the conversion of this Sample to gaseous molecules, which absorb radiation. In AAS the sample is most commonly introduced as a solution. The solution is drawn in through a little tube and carried to the nebulizer in which the remedy is broken up into a fine mist that is very similar to an aerosol can. The fine mist is transported into the atomizer, including a fire, by a carrier gas. After the mist reaches the fire, the intense heat divides the sample into its individual atoms. This last process is called atomization. There are two primary types of atomizers: discrete and continuous. Continuous atomizers present the analyte in a manner that is constant whereas discrete atomizers present the analyte discontinuously. The most popular constant atomizer in AAS is a fire, and the most popular discrete atomizer is the electrothermal atomizer.

Sample atomization restricts the accuracy, precision, and limit of detection of the analytical tool. The objective of the atomization step would be to convert the analyte into a reproducible quantity of gaseous molecules that suitably reflects the sample. Throughout electrothermal atomization, a sample gas through three Phases to attain atomization. The sample is dried in a low temperature. Then the sample is ashed in a graphite furnace discussed below, followed by a rapid temperature increase within the furnace in which the sample becomes a vapor comprising atoms from the sample. Absorption is measured over the heated surface in which the sample was atomized. A graphite furnace Is Composed of a graphite tube open at both Ends with a hole in the middle for sample introduction. The tube is encased within graphite electric contacts at both ends that serve to heat the sample.

A source of water is used to maintain the graphite furnace cool. An external flow of inert gas flows around the tube to prevent outside air from getting into the atomization atmosphere. Outside air can absorb and destroy the tube. An inner flow of inert gas flows through the tube, carrying away vapours in the sample matrix. Electrothermal atomizers provide improved sensitivity since samples are atomized fast and have a longer residence time in comparison to flame AAS systems, which means more of this sample is analysed simultaneously. This method may also be used forĀ atomic absorption spectroscopy determinations based on signal peak height and area. Electrothermal atomization also provides the benefit of smaller sample size and decreased spectral interferences due to the high temperature of the graphite furnace. But, electrothermal atomizers have disadvantages such as slow measurement time due to the heating and cooling required of the machine and a limited analytical variety.