Marine Sediment Analysis Using Inductively Coupled Plasma Optical Emission Spectrometry

Inductively coupled plasma optical emission spectrometry was applied to the determination of trace impurities in tantalum powder. The matrix effects of tantalum in the determination of trace level impurities such as Cr, Fe, Nb, Ni, and Ti were studied by measuring the intensities of each trace element in solution at various concentrations of tantalum. As the concentration of the interfering element increased, the trace sensitivity decreased similar to a linear decay, except for iron which showed a slight enhancement. The relative standard intensities of analytes in the tantalum matrix were calculated from 1000 to 20,000 mg/L tantalum solutions. The spectral line profile of the trace elements and the interference effects of tantalum at different concentrations are presented and discussed. INTRODUCTION Inductively coupled plasma optical emission spectrometry (ICP-OES) is a widely used instrumental technique for the determination of a large number of analytes at different concentration levels. ICP-OES offers high sample throughput with a wide dynamic range and is relatively free from matrix interferences. A limiting factor of the technique which affects trace elemental analysis in the presence of complex matrices is due to the transfer of main matrix elements to the plasma at the same rate as that of the trace. This can result in changes in the plasma; thus adversely influencing the analysis. Several research groups have conducted studies on the matrix interference effect, but the matrix elements studied have been restricted to alkali metals (1–9). In terms of mechanisms, matrix effects are due to ionization suppression by an excess of electrons from the easily ionizable elements (alkali metals) by increasing collision excitation as a result of the increased number of high-energy electrons. In the case of transitional elements (10,11), both atomic and ionic lines are suppressed in intensity in the presence of the interferent. This is due to ambipolar diffusion, a mechanism brought about by electrons diffusing radially out of the central channel. This would tend to drag positive ions away from the center to cause a reduction in the number of analyte ions and, therefore, decrease analyte emission intensity in this region. C-MET, Hyderabad, is actively involved in the preparation of low and high voltage capacitor-grade tantalum powder through solvent extraction and sodium reduction routes. Analysis of tantalum powder is routinely carried out using ICP-OES and many interferences are seen during the determination of Cr, Fe, Nb, Ni, and Ti. The present analytical work will be vital in regard to tantalum capacitor performance and applications.