Gravimetric preparation of synthetic mixtures of platinum isotopes

Abstract

Five synthetic isotope mixtures were prepared from isotopically enriched and purified platinum solutions to obtain accurately known isotope amount ratios n( 196Pt)/ n( 195Pt). Two metallic platinum powders enriched in isotopes 195Pt and 196Pt, respectively, were dissolved in aqua regia. The resulting hexachloroplatinic acid was reduced under hydrogen to transform it into a metallic platinum sponge. The level of impurities contained in the sponges, as well as their stoichiometry were estimated and taken into account in all calculations carried out with the isotopically enriched materials. The prepared isotope amount ratios, n( 196Pt)/ n( 195Pt), of the five mixtures were 0.099 57, 0.397 34, 0.738 00, 3.9976, and 10.005 with expanded relative uncertainty (coverage factor k = 2) varying from 1 × 10 −3 to 2.8 × 10 −3. These mixtures were used to calibrate isotope amount ratio measurements of a platinum sample of natural isotopic composition by inductively coupled plasma mass spectrometry. Keywords: Atomic weight; Platinum; Inductively coupled plasma mass spectrometry; Isotopic reference material; Synthetic isotope mixtures