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 conven tional radial viewing of the ICP. Figures of merit such as detection limit, background equivalent concen tration, 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 (SBR RSDB) 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 improve ment factor of five in detection power was observed when using axial viewing compared with radial view ing.

A new type of solid-state detector has been designed to meet the needs of inductively coupled plasma optical emission spectroscopy (ICP-OES), including high quantum efficiency in the UV, low noise, wide dynamic range, rapid readout, broad spectral coverage, and high spectral resolution. The device is based on buried-channel chargecoupled-device (CCD) technology with unique features for optical emission spectroscopy and is matched to a specific echelle grating optical system described in the companion paper. It measures simultaneously 5.7% of the continuous ICP spectrum from 167 to 782 nm with 224 linear photodetector arrays. These arrays are targeted on three to four primary analytical lines for each of 72 elements and cover over 5000 ICP emission lines. This device provides the combination of high quantum efficiency in the UV, low readout noise typical of CCDs, true random-access readout, and charge blooming control for wide dynamic range. In general, the detector has photometric performance (quantum efficiency, noise, dynamic range) equal to or better than photomultiplier tubes for ICP-OES. The simultaneously measured spectral data can be used to correct for spectral interferences and correlated background noise so that analytical detection limits are photon shot noise limited.

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