Characterization of a multimode sample introduction system (MSIS) for multielement analysis of trace elements in high alloy steels and nickel alloys using axially viewed hydride generation ICP-AES

Abstract

A commercial multimode sample introduction system (MSIS) was characterized for simultaneous multielement hydride and nonhydride-forming elements (As, Bi, Co, Cr, Fe, Mn, Mo, Ni, Sb, Se, Sn, Ti, V, W) in high alloy steels and nickel alloys by axially viewed ICP-AES. Vapor formed by the NaBH₄ reaction and aerosol from a specially designed dual conical spray chamber and pneumatic nebulizer were injected simultaneously into a robust plasma. Spectroscopic effects caused by major and minor elements and nonspectroscopic interferences induced by matrix concomitants were evaluated both for conventional nebulization and for hydride generation. The objective of the study was to establish optimized operating conditions whereby both nonhydride and hydride forming elements could be determined simultaneously. It was observed that the sensitivities of the ‘hydride generating’ elements using a MSIS, were similar to those observed using conventional hydride generation. In comparison to conventional pneumatic nebulization, hydride LODs, were enhanced significantly by factors varying from about 2–20. Limits of detection using the MSIS, for nonhydride elements (Co, Cr, Fe, Mn, Mo, Ni, Ti, V, W) were similar to those reported for the conventional sample introduction system. Several fundamental parameters such as Mg II 280.270/Mg I 285.213 nm ratios, excitation temperature (T_ex) and the effect of hydrogen were also determined. The effect of hydrogen, formed during hydride generation, on intensities of nonhydride and hydride forming elements and excitation temperature was evaluated. This is important because hydrogen can modify the properties of the ICP. The effect of variable concentrations of tartaric acid, L-cystein, EDTA, and 1,1,3,3-tetramethy-2-thiourea as retarding agents for reducing deleterious effects of Ni was investigated. The accuracy of the procedure was verified by analyzing several certified reference metallurgical samples. An important conclusion of this multielement study is that the application of the MSIS for simultaneous determination of hydride forming and non-hydride forming elements in complex metallurgical samples by ICP-AES is constrained by matrix derived spectral line interferences.