A He/Ar mixed-gas plasma has been investigated as an optical emission source for the determination of iodine at 2063 Angstroms. The effects of adding varying amounts of He to an argon plasma were studied. Optimal conditions were found with a total plasma composition of 34% helium. The auxiliary gas was 100% argon, whereas the carrier gas and the coolant gas were composed of 88% and 35% He, respectively. The mixed-gas plasma reduced the detection limit for iodine to 0.4 ppm, a sevenfold improvement over the detection limit obtained with a 100% Ar plasma. At the optimum conditions for iodine, detection limits for most other elements studied improved or stayed the same.
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