1. ICP (Inductively Coupled Plasma) - this is a high temperature plasma (ionised argon) sustained with a magnetic field, which acts to produce ions.
2. MS (Mass spectrometry) the ions from the plasma are extracted through a series of cones into a mass spectrometer, usually a quadrupole. The ions are separated on the basis of their mass-to-charge ratio and a detector receives an ion signal proportional to the concentration.
The concentration of a sample can be determined through calibration with elemental standards.
ICP-AES (Atomic Emission Spectrometer) uses the ICP to produce excited atoms which emit radiation (at a wavelength characteristic of a particular element), which can then be detected (signal is proportional to concentration).