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or coincident with, the analytical line. When the overlap is not too severe, background correction can be
performed by plotting the real background from the spectral information. When complete overlap
occurs, it is usually best to utilize an alternative line.

Q. What are the main types of spectroscopic and non-spectroscopic interferences?

Q. Why must care be exercised when using internal standardization?

Q. How would you correct for an increase in the continuum background emission caused by
aluminium?

4.4.9 Applications.

ICP-AES has been used to analyse a wide variety of sample types. It is usually necessary to present the
sample in the form of a liquid, although solids can be analysed directly in the form of slurries, by
direct insertion, laser ablation or electrothermal vaporization (see Chapter 7).

Methods that have been used to prepare samples for ICP-AES are similar to those used for flame
spectroscopy, including sample digestion with acids, fusions, solvation in organic solvents or thermal
decomposition and subsequent dissolution. Because the ICP has such a high temperature it is possible
to introduce solid samples while still achieving nearly complete atomization of the sample. This makes
it ideal for the analysis of slurried samples of refractory compounds, minerals and coals, which are
difficult to dissolve without the use of perchloric and hydrofluoric acid, or fusion methods. Biological
materials can generally be digested in one or a combination of nitric, sulphuric, hydrochloric and
phosphoric acid. Polymeric materials usually require prior thermal decomposition in a muffle furnace or
attack with a strongly oxidizing acid such as sulphuric acid. Monomers and oils can be dissolved in an
appropriate organic solvent such as methyl isobutyl ketone (MIBK) or xylene. One limitation of the ICP
is that it cannot readily accept volatile organic solvents. Unlike a chemical flame which derives its
energy from chemical oxidation of the fuel, the ICP is sustained by coupling electromagnetic energy
through a radiofrequency circuit, which sustains the collisional ionization of the support gas. If volatile
organic solvent is introduced into the plasma, the efficiency of the RF coupling will be disturbed and an
impedance mis-match will occur, causing the RF generator to operate with high reflected power,
causing damage to the generator. Modern instruments have RF matching networks or free-running
generators which can accommodate this; however, if the solvent loading is very high