AAS or Atomic Absorption Spectroscopy is a quantitative spectro-analytical procedure that is used to determine chemical elements using the absorption of optical radiation by free atoms in the gaseous state. It measures the selective absorption of light by gaseous atoms produced by spraying a solution into a FAAS flame or by evaporation in a carbon tube (CFAAS).
How AAS works?
AAS or the Atomic Absorption Spectrophotometers use the absorption of light to determine the concentration of specific metal atoms in a liquid or gas by vaporizing the sample in a graphite (GFAAS) or flame (FAAS) furnace. In the ground-state free metal, atoms are excited in the process by a certain wavelength of light. The technique can be deployed to measure the concentration of metallic elements in different materials.
Atomic Absorption Spectrophotometers use electromagnetic wavelengths coming from a light source to get a picture of what concentrations of a specific element are. What happens is the ground state of free metal atoms is excited by a specific wavelength of light. Then the difference between the background absorption and sample is measured and compared with the absorption of a series of standard solutions.
Applications
Atomic Absorption Spectrophotometers are typically used for trace metal analysis of a wide range of samples in the chemical and pharmaceutical sectors, environmental sciences, and food as well as beverage processing industry for contamination or impurity monitoring, rapid assessment of raw materials, and quality control.
The process is also used in a clinical setting for the analysis of several biological fluids such as urine and blood. As AAS is relatively straightforward to use and inexpensive and it offers high throughput for the qualitative analysis of the metal content in solids and liquids, it makes AAS suitable for use in a wide range of applications.
Types of Contaminants in water that can affect AAS Results
There are some sources of AAS interference in water. They are listed as follows:
- Particulates. The presence of particulates in standards or samples used for AAS can prevent reproducible and efficient spraying of the sample solution in the flame and lead to blockage in the atomization system. The build-up of particulate matter or blockage can also cause the drift and loss of sensitivity.
- Metal ions. As AAS has a high sensitivity, this means that the metal ions present in water can be used to prepare blanks, samples, or standards that are likely to interfere during the analysis process. Also, you need to consider the possible contamination of labware that is used for preparation.
- Organic molecules. The presence of organic molecules can also lead to debris buildup on the surface of the nebulizer hence lowering its efficiency.
Conclusion
AAS has a high sensitivity quotient which makes it crucial not to introduce the sources of contamination during the preparation of standards, blanks, and samples. Also, note that the type of water essential is related to the sensitivity of the procedure that is being employed. You must use Type II water for FAAS in most cases, whereas for the GFAAS process, Type I water is essential.
