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Atomic Absorption Spectroscopy

 What is Atomic Absorption Spectroscopy?

  • Atomic Absorption Spectroscopy deals with the absorption of a specific wavelength(λ) by neutral atoms at the ground state level atoms. These neutral atoms are obtained by spraying the sample solution of elements using a burner. A specific wavelength of radiation to determine every element.

Principle of Atomic Absorption Spectrometer
  • A solution of metallic salt is sprayed on a flame, fine droplets are formed.
  • The thermal energy of flame the solvents in the droplets evaporate, leaving fine residue, which is converted to neutral atoms.
  • These neutral atoms absorb radiation of a specific wavelength emitted by a hollow cathode lamp(HCL).
  • HCL filled with the vapour of element which gives a specific wavelength of radiation.
  • The intensity of light absorbed by neutral atoms is directly proportional to the concentration of the elements.
  • The intensity of radiation absorbed by neutral atoms is measured using photometric detectors.
Note: The excitation of neutral atoms is brought only by radiation from a hollow cathode lamp and not by the thermal energy of the flame.

Instrumentation of Atomic Absorption Spectrometer

Hollow Cathode Lamp
  • The source of light in AAS is a hollow cathode lamp.
  • The cathode is made up of specific elements or alloys of elements on the cathode.
  • when current is applied to anode and cathode, metal ions emerge from the collides with filler gas, which argon.
  • Due to these collisions, the number of metal atoms is excited and emit their characteristic radiation.
  • This radiation is absorbed by neutral atoms of the same elements in the ground state, which occur in the flame when the sample solution is sprayed.
  • The determination of every element, separate HCL has to be using multi-element lamps.
  • ex: Two elements lamps Na/K, Ca/Mg, Three elements lamps Ca/Mg/ Zn.
PEOPLE ALSO READ: SOP for Calibration of Atomic Absorption Spectrometer
  • There are different burners available, which are used to spray the sample solution into fie droplets, mix with fuel and oxidant. The most common ones are the Total consumption burner and the Laminar flow burner.
  • The instrument had choppers, which rotate as fans allow alternatively radiation from flame alone or radiation from HCL and flame.
  • This procedure a pulsating current signal, which is used to measure the intensity of light absorbed by elements, without interference by radiation from the flame itself.
  • To isolate the line spectrum of the element from the background signal of the flame. so a monochromator that can provide a good resolution of 1 nm is required.
  • The intensity of radiation absorbed by elements, in the UV or Visible region (190-800 nm) can be detected phototube or photomultiplier tube.
  • The recorder readout is capable of displaying absorption spectrum as well as absorbance at a specified wavelength.

Application of Atomic Absorption Spectrometer
  • Atomic Absorption Spectrometer is mainly used for quantitative analysis of various elements present in different samples.
  • Major of the applications are Agriculture, Forensic, Environmental, Food, Pharma, Mining, Petrochemicals industries.
  • Estimation of trace elements in biological fluids (ex: blood, urine etc).
  • Estimation of elements like copper, Nickel and Zinc, Magnesium, Zinc, mercury, Lead etc.
  • Estimation of elements in soil samples, water supply, effluent ceramics, etc.
PEOPLE ALSO READ: SOP for Operation of Atomic Absorption Spectrometer

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