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

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.

Performance evaluation of an axially viewed horizontal inductively coupled plasma for optical emission spectrometry

“…The fact that there was little overall difference among the three sets of experimental conditions suggests that the shear gas was effective in minimizing the effect of self-absorption in the axial viewing arrangement. These results are in agreement with the work of Demers [3] and confi rm that axial viewing shifted the linear range to lower concentrations while retaining a similar span in concentration as radial viewing.…”

“…Useful positions for the shearing gas nozzle were found to be in the range between 29 and 34 mm beyond the load coil. This coincided with the region identified by Demers [3] as the visible boundary between the normal analytical zone and the plume when introducing high concentrations of yttrium.…”

“…When Mn was used as the alignment element, the highest analyte emission point always coincided with the position giving the minimum background emission. Similar reports have been published in the literature for axial viewing [3][4][5][6]. Thus, the SBR was easily optimized.…”

“…(3). (3) With MSF data processing, the detection limits were produced directly after the algorithm was invoked. Consequently, BEC and RSDB values were not provided directly.…”

“…However, the linear dynamic range was reported to be similar with an overall shift to lower concentration. Conflicting conclusions have been presented concerning chemical matrix effects and the magni tude of the molecular and argon continuum background emission [2][3][4][5][6][7][8]. The discrepancies were probably the result of differences in experimental setups such as plasma source conditions, the torch and load coil geometry, the sample introduction system used, implementation of a shearing gas, etc.…”