text: The technique makes use of the atomic absorption spectrum of a sample in order to assess the concentration of specific analytes within it. It requires standards with known analyte content to establish the relation between the measured absorbance and the analyte concentration and relies therefore on the [Beer–Lambert law]. ## Analyzing Samples with Atomic Absorption Spectroscopy (AAS)
  Atomic Absorption Spectroscopy (AAS) measures the concentration of specific elements in a sample by analyzing their unique "fingerprint" in the form of an atomic absorption spectrum. Here's how it works:
  **Step 1: Sample Preparation:**
  * The sample is typically dissolved in a suitable solvent (acids, water) to create a liquid solution. This ensures the analytes are present as free atoms, ready for absorption.
  * For solid samples like ores or minerals, additional steps like grinding and digestion may be required to break down the matrix and liberate the analytes.
  **Step 2: Atomization:**
  * The prepared solution is nebulized into a fine mist and introduced into a high-temperature flame (air-acetylene or nitrous oxide-acetylene mix).
  * The intense heat in the flame excites the electrons in the analyte atoms, promoting them to higher energy levels.
  **Step 3: Absorption:**
  * Simultaneously, a hollow cathode lamp containing the same element as the analyte emits a specific wavelength of light that corresponds to the energy difference between the excited and ground state of the analyte atoms.
  * As the emitted light passes through the atomized sample, some photons are absorbed by the excited analyte atoms, causing them to return to their ground state. This absorption decreases the intensity of the light at the specific wavelength.
  **Step 4: Measurement and Analysis:**
  * The light intensity before and after passing through the sample is measured by a detector.
  * The difference in intensity is directly proportional to the concentration of the analyte in the sample, following the Beer-Lambert law:
      * **A = εcl**, where:
          * A is the absorbance measured.
          * ε is the molar absorptivity (constant specific to the element and wavelength).
          * c is the concentration of the analyte.
          * l is the path length of the light through the sample.
  **Step 5: Calibration and Quantification:**
  * To determine the actual concentration of the analyte, the instrument is calibrated using standard solutions containing known concentrations of the element.
  * By comparing the measured absorbance of the sample to the calibration curve, the concentration of the analyte in the original sample can be calculated.
  **Feedback Mechanism:**
  The measured absorbance directly provides feedback on the concentration of the analyte in the sample. This feedback loop allows the AAS to analyze various samples efficiently and determine their elemental composition with high accuracy.
  In summary, AAS utilizes the unique absorption properties of elements to accurately quantify their concentration in samples. By preparing the sample, atomizing the analytes, measuring their absorption of specific light, and applying the Beer-Lambert law, this powerful technique helps us understand the elemental makeup of diverse materials across various scientific and industrial fields.