Question

Compared to flame, ICP emission provides detection of more elements below 10ppb. Explain the reason.

Answer 1

Flame atomic absorption technique relies on ground state atoms and the absorption of light that passes through the flame containing the atoms. Especially for trace and minor concentrations and where only few elements need to be analyzed,

ICP- requires different, much higher temperatures for emission to take place for most of the elements. Because of the high temperatures present in an inductively coupled argon plasma not only atomic, but also ionic emission takes place. This is an advantage since many metals have sensitive ionic emission lines. One reason why ICP, compared to the AAS technique, provides higher detection sensitivity.

Because chemical flames are used, the maximum achievable temperatures are limited, elements with, for example, a higher affinity to oxygen may easily form oxides, which will not dissociate since the temperatures in the flame are not high enough. These so called chemical interferences are quite common and need to be addressed by using additional chemicals or different flame parameters for different elements.

In contrast, an inductively coupled argon plasma with temperatures up to 10,000K is more powerful, extremely robust and is thus less influenced by the sample introduced. It is also chemically inert and does not influence the constituents of the sample. Chemical interferences are therefore completely eliminated. ICP provides generally a higher sensitivity for metals and also enables the measurements of non-metals. Because of the high temperatures in the plasma the sensitive ionic emission lines of those elements are usable.