In one approach to perform atomic absorption spectrometry (AAS), two key components are a hollow cathode lamp and a flame. What are the functions of these two components?
The correct answer and explanation is:
In atomic absorption spectrometry (AAS), the hollow cathode lamp and the flame serve critical functions in the process of detecting specific elements in a sample.
- Hollow Cathode Lamp:
The hollow cathode lamp is the light source used in AAS. It contains a cathode made of the metal or element being analyzed. When an electrical current passes through the lamp, the metal in the cathode is vaporized and forms excited atoms. As these atoms return to their ground state, they emit light at characteristic wavelengths specific to the element in question. This emitted light is directed towards the sample. The primary function of the hollow cathode lamp is to provide a narrow beam of light at a wavelength that corresponds to the absorption characteristics of the target element in the sample. The wavelength of light emitted depends on the metal used in the cathode, ensuring that the lamp can be tailored for the analysis of different elements. - Flame:
The flame in AAS is used to atomize the sample, turning it into free atoms in a gaseous state. A small portion of the sample is introduced into the flame, where it is vaporized and atomized at high temperatures. The flame serves two main purposes:- Atomization: The flame provides sufficient energy to break the sample down into its atomic components, allowing individual atoms to absorb light at specific wavelengths.
- Excitation: The flame also excites the atoms in the sample, although this is not always necessary for the absorption process. The critical role of the flame is to ensure that the atoms are in their ground state, ready to absorb the incident light from the hollow cathode lamp.
In summary, the hollow cathode lamp provides the necessary light for atomic absorption, while the flame atomizes and excites the sample, enabling the detection and measurement of specific elements. The absorption of light by the atoms in the flame is measured and used to quantify the concentration of the element of interest in the sample.