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 vapor of elements 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.

Atomic absorption spectroscopy (AAS) is a widely used analytical technique in the pharmaceutical industry for the analysis of various elements in drug substances, drug products, and excipients. It is a sensitive and precise method that measures the concentration of specific elements in a sample by measuring the absorption of light by the atoms of the element.

In AAS, a sample is atomized and then exposed to a beam of light of a specific wavelength that corresponds to the element of interest. The atoms absorb the light, and the amount of absorption is measured by a detector. The amount of absorption is proportional to the concentration of the element in the sample.

AAS is particularly useful in the pharmaceutical industry for the determination of trace elements in drug products, which can have significant impacts on the efficacy, safety, and stability of a drug. Some of the trace elements that are commonly analyzed by AAS in pharmaceuticals include metals such as lead, arsenic, mercury, cadmium, and chromium.

AAS is also used in the analysis of the purity of drug substances and the quality of excipients used in drug formulation. It is important to ensure that the drug substance and excipients meet the required specifications for purity and quality, as these can affect the safety and efficacy of the drug product.

In summary, atomic absorption spectroscopy is an important analytical technique in the pharmaceutical industry for the analysis of trace elements in drug substances, drug products, and excipients. It provides precise and accurate measurements of specific elements and plays a critical role in ensuring the safety and efficacy of pharmaceutical products.

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 the anode and cathode, metal ions emerge from the collides with filler gas, which is 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.

  • There are different burners available, which are used to spray the sample solution into fine droplets and mix them 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 allowing alternative radiation from flame alone or radiation from HCL and flame.
  • This procedure is 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 a photomultiplier tube.

  • The recorder readout is capable of displaying the 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.
  • The major applications are Agriculture, Forensic, Environmental, Food, Pharma, Mining, Petrochemicals industries.
  • Estimating trace elements in biological fluids (ex: blood, urine, etc).
  • Estimating elements like copper, Nickel, Zinc, Magnesium, Zinc, Mercury, Lead, etc.
  • Estimating elements in soil samples, water supply, effluent ceramics, etc.

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