Line Selection and Evaluation of Radio Frequency Glow Discharge Atomic Emission Spectrometry in the Determination of Trace Amounts of Niobium in Electron Beam-melted Tantalum Sheet

Trace niobium (Nb) was determined in an electron beam-melted (EBM) tantalum (Ta) sheet by a radio frequency glow discharge optical emission spectrometry (RF-GD-OES) method using argon (Ar) as the discharge gas. The discharge operating parameters were optimized based on both the raw analyte signal intensity (S) and the signal-to-background ratio (S/B). A methodical approach was used to select a Ta interference-free line of Nb for the analysis of trace Nb in a Ta sheet based on signal-to-noise (S/N) measurements with a Model Jobin-Yvon high-resolution 1 mJY-10,000 RF monochromator having a 2400/2 grooves/mm holographic grating. The analytical lines selected were used to evaluate the degree of line interference and limits of detection. Nb determination in an EBM Ta sheet was performed to estimate the precision and accuracy of the analytical result. The relative standard deviation (RSD) of the intensity for the Nb line was around 3% for within runs and around 4% for between runs which represents the overall analytical performance of this technique on the precision; the accuracy was compared with ICP-OES analysis and was satisfactory. The detection limits for Nb in the EBM Ta sheet was estimated to be 2 μg/g. The details of sensitive line selection and sputtering parameters are presented and discussed.