Evaluation of the Axially Viewed (End-on) Inductively Coupled Argon Plasma Source for Atomic Emission Spectroscopy

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Abstract
A comparison of an “end-on” viewed argon inductively coupled plasma (ICP) operated in the horizontal position with the conventional “side-on” viewed argon ICP was carried out using the same experimental setup. The end-on ICP required an air cutoff stream located toward the tip of the luminous discharge, to protect the optics and to increase linearity ranges, and the orifice diameter of the central tube of the torch was widened to 1.9 mm, to improve line/background ratios. With the end-on viewed plasma the linearity ranges, the susceptibility to solute vaporization and to ionization matrix effects, and the detection limits in an organic solvent were insignificantly different from those observed with the side-on viewed plasma. Detection limits with aqueous samples were always significantly lower with the end-on viewed plasma, usually five- to tenfold lower, in a few instances, 20-fold lower. With the end-on viewed plasma the optimal observation region for both single and simultaneous multielement analysis is one and the same and is extremely easy to locate.