Computer simulation of argon-nitrogen and argon-oxygen inductively coupled plasmas

The properties of mixed-gas Ar-N-2 and Ar-O-2 inductively coupled plasmas (ICPs) are obtained by computer simulation. The results from the simulations are compared with existing experimental data. The reasons for the deviations are discussed, and inferences are drawn to connect the simulated results to recommendations for practical analytical measurements using ICP atomic emission and ICP mass spectrometries. The effect of the concentration of N-2 and O-2 in the outer gas flow (0%-100%) and injector gas flow (0%-20%) and the influence of the active power (800-1500 W) on the distribution of the plasma temperatures, electric and magnetic fields and tangential velocity are investigated. In general, mixed-gas plasmas move closer to the state of local thermodynamic equilibrium (LTE) as the concentrations of the molecular gases (N-2 and O-2) in the outer gas flow are increased. In contrast with the experimental results, the LTE model predicts that mixed-gas plasmas have maximum temperatures (9900-10 100 K) comparable with Ar ICPs (10 600 K). The predicted temperature of the mixed-gas plasma is reduced as the concentration of the molecular gas is increased. The temperatures of A-O-2 ICPs are estimated to be higher than those of Ar-N-2 plasmas, except when the outer gas flow contains 100% N-2 or O-2. (C) 1997 Elsevier Science B.V.