Atomic Absorption Spectroscopy (AAS) is a highly sensitive evaluation method in which the absorption of free atomic light is measured, and the concentration of the desired element is determined based on the level of absorption. The detection limit for elements can range from parts per million (ppm) to parts per billion (ppb), depending on the method used. This technique is commonly used in analytical chemistry to determine the concentration of specific elements in a sample. Additionally, AAS analysis is a widely used method for detecting metals and metalloids in extracted environmental samples. In this technique, similar to ICP analysis, the material must be digested and dissolved into a solution.
Atomic Absorption Spectroscopy (AAS) is an evaluation method in which the optical absorption of free atoms is measured, and the concentration of the target element is calculated by examining the amount of absorption. In this method, spectral absorption is used to assess the concentration of the analyte in a given sample.
Based on Beer-Lambert’s Law, the relationship between the amount of absorption and the analyte concentration is determined. According to this law, the valence electrons of an atom are excited when they receive a specific amount of energy in the form of radiation at a particular wavelength, causing them to transition to higher orbitals for a very short period (nanoseconds). The amount of energy absorbed varies for different atoms. Generally, each wavelength is specific to a particular element, meaning each element responds only to a specific wavelength. The absorption line width does not exceed a few picometers, which gives this technique the ability to accurately select elements.
The intensity of radiation is measured both in the absence of a sample and in the presence of a sample using a detector, and the absorption ratio between them is linked to the analyte concentration using Beer-Lambert’s Law. When the electron returns to its lower energy level, the initially absorbed energy is emitted as visible light, and the emitted wavelength is directly related to the electronic transition that occurred.
Since each element has a unique electronic structure, the wavelength of the emitted light is also specific to each element. The orbital structure of larger atoms is complex, allowing for a greater number of possible electronic transitions, leading to the emission of specific wavelengths. The more atoms of the studied element present, the greater the intensity of the emitted light at that specific wavelength.
Atomic Absorption Spectroscopy has a wide range of applications, including:
1. Water analysis: Detecting elements such as calcium, magnesium, iron, aluminum, and others.
2. Food industry analysis: Examining the presence of tin in canned goods such as fruit juices.
3. Geological analyses: Analyzing soil, rocks, fossils, and more.
4. Clinical analysis: Examining blood samples such as plasma and serum for calcium, magnesium, lithium, sodium, potassium, and iron.
5. Environmental analysis: Monitoring environmental conditions by measuring element levels in rivers, drinking water, air, and seawater.
6. Pharmaceutical analysis: Small amounts of metallic catalysts are used in many drug manufacturing processes, and this method helps identify these quantities in the final pharmaceutical product.
7. Industrial analysis: Checking for key elements and toxic impurities in raw materials. For example, in concrete, where calcium is a major component, lead levels must remain low due to its toxicity.
8. Mining analysis: This method helps determine the quantities of metals such as gold in rocks, aiding decisions on excavation and gold extraction.
9. Plant analysis.
10. Element analysis in the cosmetics industry.
11. Separation of nearly all metals, metalloids, and many non-metals such as silicon and phosphorus.
1. Sample Preparation
The sample must be free from impurities and contaminants, as they can affect the accuracy of the results.
In some cases, the sample may need to be dissolved in a suitable solvent or converted into a liquid form for effective analysis.
2. Sample Size
Appropriate quantity: The sample size must be sufficient to ensure accurate measurements. Although AAS analysis typically requires small amounts, they must be enough to generate a measurable signal.
1. Spectral Data Analysis
Absorption Spectrum: The absorption spectrum obtained from AAS shows the intensity of absorbed light at specific wavelengths. Each element has a unique wavelength that is measured.
Wavelength Selection: Ensuring that the selected wavelength matches the target element. The chosen wavelength must fall within the element’s absorption range.
2. Measuring Absorption Intensity
Absorption Intensity: Reflects the concentration of the element in the sample. The higher the absorption intensity, the higher the element’s concentration.
Comparison with Reference Samples: The absorption intensity is compared with reference samples or known standards to determine the precise concentration of the element in the sample.
3. Applying Beer-Lambert’s Law
Beer-Lambert’s Law: This law is used to correlate absorption intensity with element concentration.