Analytical applications of nitrogen plasma generated by ac and dc fields

The operating characteristics of a trace atomic and molecular excitation source based upon the energy transfer from metastable nitrogen molecules was investigated. A dielectric discharge through flowing nitrogen generates a large population of metastable molecules that are then mixed with the vaporized species in a reaction cell. A computer controlled tungsten filament was developed to vaporize metal species present in aqueous solutions in the reaction cell. Results obtained for the detection limits and linear dynamic working ranges for a number of metals are comparable with other detectors already in use. Although the dielectric produced active nitrogen exhibits a large concentration of metastable molecules, there is not enough energy to collisionally decompose the molecular species. To solve this problem the author proposed the use of a glow discharge to break down the analyte species. The combination of both the glow and the dielectric discharges proved to be very successful. Results obtained for the detection limits and linear dynamic working ranges for both metal chelates and organic species are comparable, and in some cases even better, than the ones obtained by other active nitrogen-based detectors