ICPAES ICPOES n n n Inductively coupled plasmas

ICP-AES (ICP-OES) n n n Inductively coupled plasmas are at least 2 X as hot as flames or furnaces. The Ar plasma is the result of the flow of Ar ions in a very strong, localized radio field. 6000 -10000 K are common. Hot enough to excite most elements so they emit light. Hot enough to prevent the formation of most interferences, break down oxides and eliminate most molecular spectral interferences. The way to do atomic emission spectroscopy today.

How does ICP work? üRadio frequency electrical current and associated magnetic field üIonization of Ar gas (sparked by a Tesla coil) üAcceleration of ions and electrons by magnetic field üEnergy in transferred from the electrons to the gas by collision so the gas is heats up. üProduction of high concentartion of both EXCITED ATOMS and ions

Plasmas gas or Three gases Support gas or auxiliary gas

How to measure temperature? n n n The plasma is thermodynamic equilibrium Cannot characterize a single temperature Four temperatures can be used n n Excitation Temp (Texc): measure of population density of the energy levels (Boltzman equilibrium) Ionization Temp (Tion): measure of population density of different ionization states (Saha equilibrium) Electron Temp (Te): a measure of the kinetic energy of the electrons (related to the velocity of free electrons) Gas Temp (Tg or T kinetic): a measure of the kinetic energy of the atoms. Tg < Texc < Tion < Te N 1/N 0 = g 1/go exp(∆E/k. T)

Hydride generation 3 BH 4 - +3 H+ +4 H 3 As. O 3 3 H 3 BO 3 + 4 As. H 3 + 3 H 20

Performance characteristics n Elements determined n n Line selection n n Better than AAS Interferences n n n Most elements have several lines that can be selected Linear range n n ~ 60 elements Chemical interferences (lowered) Spectral interferences (still a problem) Detection limits n Comparable or better than other atomic spectral techniques