1. What is Atomic absorption spectroscopy (AAS) ?
               
                Atomic absorption spectroscopy (AAS) is a spectroanalytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation (light) by free atoms in the gaseous state.
                In analytical chemistry the technique is used for determining the concentration of a particular element (the analyte) in a sample to be analyzed. AAS can be used to determine over 70 different elements in solution or directly in solid samples used in pharmacology, biophysics and toxicology research.
Atomic absorption spectroscopy was first used as an analytical technique, and the underlying principles were established in the second half of the 19th century by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, both professors at the University of Heidelberg, Germany.
              Atomic absorption spectrometry has many uses in different areas of chemistry such as:

• Clinical analysis: Analyzing metals in biological fluids and tissues such as whole blood, plasma, urine, saliva, brain tissue, liver, muscle tissue, semen
• Pharmaceuticals: In some pharmaceutical manufacturing processes, minute quantities of a catalyst that remain in the final drug product
• Water analysis: Analyzing water for its metal content.                                                                          How it works
  Atoms of different elements absorb characteristic wavelengths of light. Analysing a sample to see if it contains a particular element means using light from that element. For example with lead, a lamp
  containing lead emits light from excited lead atoms that produce the right mix of wavelengths to be
  absorbed by any lead atoms from the sample. In AAS, the sample is atomised – ie converted into
  ground state free atoms in the vapour state – and a beam of electromagnetic radiation emitted from
  excited lead atoms is passed through the vaporised sample. Some of the radiation is absorbed by the lead atoms in the sample. The greater the number of between 1 Nm–2 and 5 Nm–2. The ionisation of some gas atoms occurs by applying a potential difference of about 300–400 V between the anode and the cathode. These gaseous ions bombard the cathode and eject metal atoms from the cathode in a process called sputtering. Some sputtered atoms are in excited states and emit radiation characteristic of the metal as they fall back to the ground state – eg Pb* → Pb + h (Fig. 2). The shape of the cathode concentrates the radiation into a beam which passes through a quartz window, and the shape of the lamp is such that most of the sputtered atoms are redeposited on the cathode.
   

  Atomic Absorption Theory

  Atomic absorption spectroscopy relies on the Beer-Lambert law to determine the concentration of a particular analyte in a sample. The absorption spectrum and molar absorbance of the desired sample element are known, a known amount of energy is passed through the atomized sample, and by then measuring the quantity of light it is possible to determine the concentration of the element being measured. Aurora’s TRACE AI1200 and TRACE 1300 Atomic Absorption Spectrometers are available with flame, graphite furnace and vapor hydride generation atomizers. These atomizers aspirate the sample into the light path where it is illuminated by a hollow-cathode lamp (HCL), which emits light at the wavelength characteristic of the desired elements. A built-in detector measures the light emissions both in presence and absence of sample, and the ratio of the absorbances are used to determine the analyte concentration.