Gas-Sampling Glow Discharge for Optical Emission Spectrometry. Part II: Optimization and Evaluation for the Determination of Nonmetals in Gas-Phase Samples

Abstract

A new gas-sampling glow discharge (GSGD) is evaluated for the continuous determination of C, F, Cl, and S in molecular gases and organic vapors by optical emission spectrometry, with the use of helium as the discharge gas. Discrete aliquots of the sample are introduced into an exponential dilutor and carried by the support gas through a silica capillary tube and into the glow discharge. Radiation from the plasma source is viewed axially. The effects of plasma operating parameters such as power and pressure are studied, and emission lines of C, F, Cl, and S measured. Analytical performance is evaluated under conditions found to be optimal for each element, as well as under compromise conditions chosen for the simultaneous detection of all four elements. In both cases, detection limits in the low ng/s range, good precision (RSD < 5%), and dynamic ranges of 2–3 decades were observed for the four elements. The utility of this He–GSGD for the determination of elemental ratios in organic compounds is also investigated.