Trace Element Determinations in a Low-Alloy Steel Standard Reference Material by Isotope Dilution, Spark Source Mass Spectrometry

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Abstract
A stable isotope dilution procedure using the spark source mass spectrograph was developed for the simultaneous determination of cerium, copper, neodymium, selenium, silver, tellurium, and zirconium in a low-alloy steel material. Except for copper, the elements were present at trace concentrations that are difficult to determine by most analytical methods. In the procedure, known amounts of the isotopically enriched elements were added to 100-mg samples, which were dissolved in perchloric and hydrofluoric acids. After evaporation of the solutions almost to dryness, dissolution of the residues, and addition of hydrofluoric acid to complex the iron, the resulting solutions were electrolyzed in polytetrafluoroethylene cells. The electrodeposit on high purity, gold cathode wires was sparked in the mass spectrograph and the isotope ratios of the isotopically equilibrated elements were measured. The concentrations, ranging from 0.041% for copper to 3.1 µ/g (ppm) for neodymium, were calculated from the general isotope dilution equation. The low-alloy steel is available from NBS as Standard Reference Material 1261.