Introduction to AAS component parts

“A day spent without learning something is a day wasted”

— Anonymous

Atomic absorption occurs when a ground state atom absorbs light of a specific wavelength.The amount of light absorbed is governed by Beer Lambert’s law and will increase as the number of atoms of the element in the light path increases. The component parts of Atomic Absorption Spectrometer are similar to a UV -Vis spectrophotometer as both operate on same principle with a basic difference that the sample cell of UV-Vis spectrophotometer is replaced by an atomization source (flame or graphite furnace)

AAS Schematic Diagram

AAS Schematic Diagram

 Light sources – Hollow Cathode Lamps

The light source commonly used is a hollow cathode lamp. A different element hollow cathode lamp is required for each element determination. Cathode is made of same metal that is to be estimated in the sample

Single element lamps are used commonly though multi-element lamps are also available

Lamps are made of glass with quartz windows and filled with an inert gas such as argon

Light sources – Electrodeless Discharge Lamps

Used for volatile elements such as As,Sb, Sn,Cd,Pb, etc

EDL’s have greater lamp life and high energy throughput

Burner system

The burner assembly comprises of nebulizer to reduce the liquid sample to a fine aerosol, a spray chamber and a burner head which is used to generate a flame to produce atoms of the same elements that are present in the sample.

Monochromator

A monochromator disperses the incident light beam and permits the selected wavelength to reach the detector.

Detector

Detector commonly used is a photomultiplier tube which produces a signal proportional to the amount of light received by it.

In this section you shall be introduced to two working configurations, namely single beam and double beam instruments

Single Beam Schematic Diagram

Single Beam Schematic Diagram

Light from the source is modulated electronically or chopped mechanically by rotating chopper. This helps isolate and remove sample cell emissions from light emitted by the source. The specific wavelength isolated by monochromator is led to the detector and the electrical signal generated is proportional to the elemental concentration in the sample

Double Beam Schematic

Double Beam AAS Schematic Diagram

Double Beam AAS Schematic Diagram

 Light beam from source is split into two teams by the chopper. One beam passes directly through the flame and the other beam passes round the flame. Detector response represents the ratio of sample and reference beams. Fluctuations in light intensity are eliminated electronically to get greater reliability of results.

The sensitivity is lower than single beam instruments but the popular acceptance of double beam configuration is due to advantage of elimination of background changes in the atomizer.

The individual parts are described in more detail in subsequent modules. 

About Dr. Deepak Bhanot

Dr Deepak Bhanot is a seasoned professional having nearly 30 years expertise beginning from sales and product support of analytical instruments. After completing his graduation and post graduation from Delhi University and IIT Delhi he went on to Loughborough University of Technology, UK for doctorate research in analytical chemistry. His mission is to develop training programs on analytical techniques and share his experiences with broad spectrum of users ranging from professionals engaged in analytical development and research as well as young enthusiasts fresh from academics who wish to embark upon a career in analytical industry.

Comments

  1. thank you for this interesting course, will i get a certificate at the end of the course?

  2. remmy sikazwe says:

    Thank you gor the good works.waiting for the course to be launched

  3. Very clear and concise. Thank u for your efforts !

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