The sample is nebulized and entrained in the flow of plasma support
gas, which is typically Ar. The plasma torch consists of concentric quartz
tubes, with the inner tube containing the sample aerosol and Ar support
gas and the outer tube containing an Ar gas flow to cool the tubes (see
schematic). A radiofrequency (RF) generator (typically 1-5 kW @ 27 MHz
or 41 MHz) produces an oscillating current in an induction coil that wraps
around the tubes. The induction coil creates an oscillating magnetic field,
which produces an oscillating magnetic field. The magnetic field in turn
sets up an oscillating current in the ions and electrons of the support
gas. These ions and electrons transfer energy to other atoms in the support
gas by collisions to create a very high temperature plasma. |
Schematic cross-section of an ICP
 |