Performance evaluation of an axially viewed horizontal inductively coupled plasma for optical emission spectrometry
A performance evaluation of a horizontal axially viewed inductively coupled plasma (ICP) for optical emission spectrometry is presented. The main contribution of this work is the elucidation of the sources of analytical performance differences using practical diagnostics in the comparison of axial and conventional radial viewing of the ICP. Figures of merit such as detection limit, background equivalent concentration, precision, and dynamic range are compared for both viewing arrangements. The detection limit improvements, with axial viewing, known from previous work in the literature, are shown to be understood in the context of the signal-to-background-ratio relative-standard-deviation-of-the-background (SBRRSDB) theory. The usefulness of the SBR-RSDB approach as a diagnostic tool for understanding the detection limit improvement and identifying performance differences is demonstrated. This approach can be further utilized for quality control and quality assurance of instrument performance and detection limit results. Other characteristic differences between axial and radial viewing are presented including matrix effects on line signals and the magnitudes of spectral interferences from OH bands. An overall improvement factor of five in detection power was observed when using axial viewing compared with radial viewing.