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Simulated Supercritical Fluid Chromatography Mobile Phase Introduction to a Helium Microwave-Induced Plasma: Effects on Nonmetal Emission and Spectral Behavior

Volume 44, Number 6 (July 1990) Page 1020-1027

Webster, Gregory K.; Carnahan, Jon W.

The effects of the introduction of capillary supercritical fluid chromatography mobile phases, CO2 and N2O, into a helium microwave-induced plasma (He-MIP) are investigated. The plasma and mobile-phase flow rates are maintained at conditions comparable to those typically used for these systems. Spectral characteristics are monitored in both the ultraviolet-visible and near-infrared regions. Molecular bands from these "foreign" gases are assigned and their relative intensities are noted as a function of the doping gas flow rate. Possible molecular band interferences are noted for nonmetal atomic emission determinations with He-MIPs. Nonmetal atomic emission reduction by these gases is studied with the use of chlorine atom and ion lines as test signals. Decreases in chlorine atom and ion emission are seen as CO2 and N2O flow rates are increased. It is found that ion line emission intensity is reduced more significantly than atom line emission. Reduction of both atom and ion line emission is more pronounced with CO2 than with N2O. The electron density of the plasma does not change as the CO2 flow rate is increased from 0 to 0.25 mL (STP)/min.