GAS-SAMPLING GLOW-DISCHARGE FOR OPTICAL-EMISSION SPECTROMETRY .2. OPTIMIZATION AND EVALUATION FOR THE DETERMINATION OF NONMETALS IN GAS-PHASE SAMPLES

A new gas-sampling glow discharge (GSGD) is evaluated for the continuo us determination of C, F, Cl, and 5 in molecular gases and organic vap ors by optical emission spectrometry, with the use of helium as the di scharge gas. Discrete aliquots of the sample are introduced into an ex ponential dilutor and carried by the support gas through a silica capi llary tube and into the glow discharge. Radiation from the plasma sour ce is viewed axially. The effects of plasma operating parameters such as power and pressure are studied, and emission lines of C, F, C1, and 5 measured. Analytical performance is evaluated under conditions foun d to be optimal for each element, as well as under compromise conditio ns 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 elem ents. The utility of this He-GSGD for the determination of elemental r atios in organic compounds is also investigated.