Emission spectrum analysis (ESA) still plays an important role in the analytical world, despite the development of new analytical techniques such as AAS or ICP. ESA is popular because of the high detection sensitivity and low costs and time expenditure involved when compared to other analytical techniques. Its principle is simple: a sample is introduced to a flame, and thermal energy excites the outer valence electrons, raising them to a higher level of energy. On returning to their original state, the electrons emit the energy previously absorbed again in the form of light energy. The spectrum emitted is element-specific and can be analysed in a spectrometer.

The most frequent application of emission measurement with a flame is for determining alkali metals in pharmaceutical analysis. The method is extremely sensitive and simple to realise.

High-purity inert material which does not disrupt the spectrum analysis is required for introducing the sample to the flame. Different ceramic materials and graphite that exhibit the best prerequisites can be used for this purpose. Spectrally pure rods made of extruded electrographite normally provide purities < 2ppm in this context.