Atomic Emission Spectrometry:

You have learnt in detail about the underlying principles, instrumentation and applications of atomic absorption spectrophotometry (AAS). You would recall that in AAS the atomic vapours in the ground state absorb the characteristic radiation of the element and the absorbed radiation and its intensity form the basis for the qualitative and quantitative applications. In contrast to this, in the current unit we take up atomic emission spectrometry (AES) that concerns the emission of radiation by the suitably excited atomic vapours of the analyte. Here, the emitted radiation and its intensity form the basis for the qualitative and quantitative applications of the technique. AES is one of the oldest spectroscopic methods of analysis. It is a multi- element analytical technique that can be used for the analysis of materials in gaseous, liquid, powder or solid form. Its high detection power and wide variety of excitation sources makes it the most extensivel y used method for analysis. Of the various different atomic emission spectrometric methods we would deal with the one in which an inductively couple plasma (ICP) acts as an atomisation- excitation source; the technique being called ICP-AES. A number of elements which could be determined concurrently are only limited by the availability of sufficiently sensitive interference free spectral lines.

We begin the unit with an explanation of the origin of atomic emission spectrum and learn about the principle behind atomic emission spectrometry being used as an important analytical technique. After that we will take up the instrumentation required for the measurement of atomic emission spectrum. An account of the analytical methodology for qualitative and quantitative applications of AES will be followed by the possible interferences in atomic emission spectrometry. In the next unit you would learn about the applications of atomic absorption spectrophotometry and atomic emission spectrometry in diverse areas.

Objectives

After studying this unit, you will be able to:

• Elaborates the principle of atomic emission spectrometry,
• Enlist several excitation sources for atomic emission spectrometry,
• Define the different types of plasma sources and nebulisers used in ICP-AES,
• Define the methods of solution preparation for AES,
• Draw a schematic diagram describing different components of an atomic emission spectrometer,
• Compare and contrast the various types of instruments used for ICP-AES,
• Describes the qualitative determination strategy of AES using appropriate examples,
• Outline the quantitative methodology of the atomic emission spectrometry using ICP as the source,
• Define the interferences observed in atomic emission spectrometric determinations using ICP, and
• State a few applications of atomic emission spectrometry based on ICP.