Atomic Emission Spectroscopy

The main components of an atomic emISSIOn spectrometer are an atomization and ionization cell, a method of sample introduction, the spectrometer and detector. In contrast to AAS, no radiation source is required.

Flame photometry is almost exclusively used for the determination of alkali metals because of their low excitation potential (e.g. sodium 5.14eV and potassium 4.34eV). This simplifies the instrumentation required and allows a cooler flame (air-propane, air-butane or air-natural gas) to be used in conjunction with a simpler spectrometer (interference filter). The use of an interference filter allows a large excess of light to be viewed by the detector. Thus, the expensive photomultiplier tube is not required and a cheaper detector can be used, e.g. a photodiode or photoemissive detector. The sample is introduced using a pneumatic nebulizer as described for FAAS. Flame photometry is therefore a simple, robust and inexpensive technique for the determination of potassium (766.5 nm) or sodium (589.0 nm) in clinical or environmental samples. The technique suffers from the same type of interferences as in FAAS. The operation of a flame photometer is described in Box 26.2.