The simultaneous determination of osmium,ruthenium, iridium and gold in platinum by neutron activation analysis

Osmium, ruthenium, iridiuim and gold can be determined simultaneously in 100-mg platinum samples after irradiation for 11 days at a thermal neutron flux of 4'1011 n.cm^-2.sec^-1. An addition method of analysis is used; samples are dissolved in small sealed silica tubes before activation. After irradiation, Os and Ru are distilled from sulfuric acid-sodium bromate, Ru being determined by counting the 498-keV peak of ¹⁰³Ru; Os is determined after a second distillation. Gold is extracted with ethyl acetate from the residue of the first distillation; the ratio ¹⁹⁸Au/¹⁹⁹Au is a direct measure for the gold content, with appropriate correction for the second-order reaction ¹⁹⁶Pt(n,γ)¹⁹⁷Pt→¹⁹⁷Au(n,γ)¹⁹⁸Au. Ir is determined in the residual aqueous phase using the 317-keV peak of ¹⁹²Ir; a correction for the platinum activity (¹⁹¹Pt) is made. The lower limit of determination is ca. 0.5 p.p.m. for ruthenium, ca. 0.2 p.p.m. for osmium, ca. O.1 p.p.m. for gold and ca. O.1 p.p.m. for iridium. After a separation of Pt from Ir, the sensitivity for Ir can easily be improved to < 10 p.p.b.