PERFORMANCE EVALUATION OF AN AXIALLY VIEWED HORIZONTAL INDUCTIVELY-COUPLED PLASMA FOR OPTICAL-EMISSION SPECTROMETRY

A performance evaluation of a horizontal axially viewed inductively co upled plasma (ICP) for optical emission spectrometry is presented. The main contribution of this work is the elucidation of the sources of a nalytical performance differences using practical diagnostics in the c omparison 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 arrangeme nts. The detection limit improvements with axial viewing, known from p revious work in the literature, are shown to be understood in the cont ext of the signal-to-background-ratio relative-standard-deviation-of-t he-background (SBR-RSDB) theory. The usefulness of the SBR-RSDB approa ch as a diagnostic tool for understanding the detection limit improvem ent and identifying performance differences is demonstrated. This appr oach can be further utilized for quality control and quality assurance of instrument performance and detection limit results. Other characte ristic differences between axial and radial viewing are presented incl uding matrix effects on line signals and the magnitudes of spectral in terferences from OH bands. An overall improve ment factor of five in d etection power was observed when using axial viewing compared with rad ial viewing.