Inductively coupled plasma chemistry examinations with visible acousto-optic tunable filter hyperspectral imaging

Abstract

Inductively coupled plasma optical emission spectrometry (ICP-OES) is widely used in trace-metal analysis. However, the behavior of this hot, ionized gas and effects on analyte excitation and ionization is not fully understood. To obtain sufficient information on the characteristics of plasma, two previous approaches, Abel inversion and tomography, have been used. Major drawbacks of these approaches include complex optical and data manipulation systems, significant amounts of time required for data collection, and long-term plasma drift and flicker. Initial examinations of an approach to alleviate many of these problems are presented. A hyperspectral imaging (HSI) system using an acousto-optic tunable filter (AOTF) as a wavelength selection device and a charge coupled device (CCD) camera as a detector is described. In these studies, the behavior of a visible paratellurite AOTF is presented. Six elements that yield intense emission lines in the visible wavelength region were examined. With in-house written software, plasma image background correction was achieved in a rapid fashion. Plasma chemistry was studied while varying plasma conditions including the applied rf power, nebulizer sample carrier gas flow, and liquid sample delivery rate. Results indicate that correlations between elemental excitation and ionization energies and the enhancements on emission intensities could be clearly discerned. It is demonstrated that the AOTF-HSI system has the potential to be a powerful tool for plasma chemistry research.