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A 22 mm torch has been developed and characterized for use in inductively coupled plasma atomic emission spectrometry. A stability curve (radio-frequency power vs. outer-gas flow rate) was constructed for
the modified torch which indicates that the larger torch can be operated at flow rates and powers similar to those for an 18 mm torch. Four operating parameters were optimized by means of a simplex algorithm.
Several criteria for optimization were used, including net signal intensity for Ca(II); signal-to-background noise (S/NB) for Ca(II), Mg(II), and Fe(II); and the Mg(II)/Mg(I) line intensity ratio. The results
from these simplex optimizations are compared. Mg(II)/Mg(I) was used as the final criterion for optimization for both the 22 mm and the conventional 18 mm torches. Two-dimensional spatial images of the
larger plasma were compared with those of a conventional plasma (18 mm) for a variety of plasma emission features. Detection limits were determined in two ways for a suite of analytes under conditions optimized
for the Mg(II)/Mg(I) ratio. The 18 mm torch affords the better limits of detection by an averaged factor of 1.5 because its smaller volume gives a lower background level. Finally, nitrogen molecular-ion
emission maps were collected from both the 22 mm and a conventional 18 mm plasma as an indicator of the degree of air entrainment in the plasma. Several spatial regions of the plasma have been evaluated
on the basis of the local intensity of N2+ emission for their applicability for use in atomic emission and atomic mass spectrometry. The 22 mm torch shows a larger region in and around the central channel
of low or zero N2+ emission and so may be better suited for sampling into a mass spectrometer.
The Society publishes the internationally recognized, peer reviewed journal, Applied Spectroscopy, which is available both in print and online. Subscriptions are included with membership or can be purchased by institutional or corporate organizations. Abstracts may be viewed free of charge. Previously published as Bulletin (Society for Applied Spectroscopy)