Trace metal studies on composition of materials has been the oldest branch of analytical chemistry. Traditional gravimetric techniques still constitute the backbone of most undergraduate educational laboratories but instrumental methods are fast replacing them due to advantages of speed and precision. Atomic Absorption Spectroscopy to this day has maintained a top-notch in most of the academic and industrial laboratories due to its affordability and range of applications.
Bunsen and Kirchoff studied the sodium spectrum and came to the conclusion that every element has its own unique spectrum in the vapour phase implying that a metal in atomic state can absorb radiation at same wavelength at which it emits it. This is the founding principle of atomic absorption spectroscopy. In 1859 Kirchoff showed that the Fraunhofer lines in the sun’s spectrum were atomic lines due to presence of various elements in the sun’s atmosphere.
Spectrochemical analysis had its origins with the work of Bunsen and Kirchoff but found little application until 1930’s. Modern Atomic Absorption Spectroscopy began in 1955 by a team of Australian scientists led by Alan Walsh at CSIRO (Commonwealth Science and Industry Research Organization) division of chemical physics, Australia. Walsh suggested the use of hollow cathode lamps to provide the appropriate wavelength and use of a flame to generate neutral atoms that would absorb the incident radiation in proportion to the concentration present in the traversed path.
Early day instruments did not have much limitations but the technique had its own inherent limitations such as
- Flame is not an ideal atomizer because of partial atomization, loss of sensitivity due to background interference and only a fraction of sample reaching the flame due to nebulization and passes quickly through the light path
- Sample has to be in liquid form and therefore solids will require pretreatment and digestions
- Only one element can be analyzed at a time
Modern developments and advances in electronics and automation did not eliminate such limitations but made it possible to increase laboratory throughput through features such as:
- Introduction of nitrous oxide – acetylene flame by Willis in 1965. It extended the number of elements which could be determined due to higher flame temperatures.
- Introduction of techniques such as mercury hydride analysers afforded greater accuracy and precision for analysis of metals like Hg,Pb,Sn,As,etc.
- High energy sources such as electrodeless discharge lamps for analysis of volatile elements
- Multi element lamps for faster analysis of number of elements in a sample
- Electrically heated graphite furnace analyzers for greater precision and handling of small sample amounts for lower detection limits
- Introduction of background correction techniques
- Multi – lamp holders to expedite warm up prior to analysis
Several manufacturers utilize the advanced features and provide their advantages in competitive environment. Some of the reputed manufacturers are :
- Perkin Elmer
- Agilent technologies
- Analytik Jena AG
- GBC Scientific Equipment Pty Ltd
- Thermo Fisher Scientific
- Buck Scientific
- Teledyne Leeman labs
- Aurora Instruments