[1] The application of multiple collector inductively coupled plasma source mass spectrometry (MC-ICPMS) to 176Lu-176Hf and 92Nb-92Zr chronometry has been hampered by complex Zr-Hf purification procedures that involve multiple ion exchange column steps. This study presents a single-column separation procedure for purification of Hf and Lu by ion exchange using Eichrom® Ln-Spec resin. The sample is loaded in pure HCl, and element yields are not dependent on the sample matrix. For 92Nb-92Zr chronometry, a one-column procedure for purification of Zr using Biorad® AG-1-× 8 resin is described. Titanium and Mo are completely removed from the Zr, thus enabling accurate 92Zr measurements. Zirconium and Nb are quantitatively separated from rock samples using Eichrom Ln-Spec resin, allowing measurements of Zr/Nb with a precision of better than ±5% (2σ). The Ln-Spec and anion resin procedures may be combined into a three-column method for separation of Zr-Nb, Hf, Ta, and Lu from rock samples. For the first time, this procedure permits combined isotope dilution measurements of Nb/Ta, Zr/Hf, and Lu/Hf using a mixed 94Zr-176Lu-180Hf-180Ta tracer. Analytical protocols for Zr and Hf isotope measurements using the Micromass Isoprobe, a second generation, single-focusing MC-ICPMS, are reported. Using the Isoprobe at Munster, 2σ external precisions of ±0.5ɛ units for Hf and Zr isotope measurements are achieved using as little as 5 ng (Hf) to 10 ng (Zr) of the element. The 176Hf/177Hf and Lu/Hf for rock reference materials agree well with other published MC-ICPMS and thermal ionization mass spectrometry (TIMS) data.

Separation of high field strength elements (Nb, Ta, Zr, Hf) and Lu from rock samples for MC‐ICPMS measurements

Age dating of nuclear material can provide insight into source and suspected use in nuclear forensic investigations. We report here a method for the determination of the date of most recent chemical purification for uranium materials using the 235U-231Pa chronometer. Protactinium is separated from uranium and neptunium matrices using anion exchange resin, followed by sorption of Pa to an SiO2 medium. The concentration of 231Pa is measured by isotope dilution mass spectrometry using 233Pa spikes prepared from an aliquot of 237Np and calibrated in-house using the rock standard Table Mountain Latite and the uranium isotopic standard U100. Combined uncertainties of age dates using this method are 1.5 to 3.5 %, an improvement over alpha spectrometry measurement methods. Model ages of five uranium standard reference materials are presented; all standards have concordant 235U-231Pa and 234U-230Th model ages.

235U–231Pa age dating of uranium materials for nuclear forensic investigations

Fluoride complexation of element 104, rutherfordium (Rf), produced in the 248Cm(18O,5n)261Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchange chromatographic behavior of Rf was investigated in 1.9-13.9 M hydrofluoric acid together with those of the group-4 elements Zr and Hf produced in the 18O-induced reactions on Ge and Gd targets, respectively. It was found that the adsorption behavior of Rf on anion-exchange resin is quite different from those of Zr and Hf, suggesting the influence of relativistic effects on the fluoride complexation of Rf.

Fluoride complexation of element 104, rutherfordium.

Chemical studies on element 104, rutherfordium (Rf), at JAERI (Japan Atomic Energy Research Institute) are reviewed. The transactinide nuclide 2 6 1 Rf has been produced in the reaction 2 4 8 Cm( 1 8 O, 5n) at the JAERI tandem accelerator with the production cross section of about 13 nb. On-line anion-exchange experiments on Rf together with the lighter homologues, group-4 elements Zr and Hf, in acidic solutions have been conducted with a rapid ion-exchange separation apparatus. From the systematic study of the anion-exchange behavior of Rf, it has been found that the properties of Rf in HCl and HNO 3 solutions are quite similar to those of Zr and Hf, definitely confirming that Rf is a member of the group-4 elements. However, we have observed an unexpected chemical behavior of Rf in HF solutions; the fluoride complex formation of Rf is significantly different from those of the homologues. Prospects of extending chemical studies on transactinide elements in the near future at JAERI are briefly considered.

Chemical studies on rutherfordium (Rf) at JAERI

Investigations of chemical properties of the heaviest elements are among the most fundamental in all of chemistry. They seek to probe the uppermost reaches of the periodic table of the elements where the nuclei are unstable and relativistic effects on the electronic shells are very strong. Theoretical research in this area is extremely important. It is often the only source of useful chemical information. It also enables one to predict behaviour of the heaviest elements in the sophisticated and expensive experiments with single atoms. Spectacular developments in the relativistic quantum theory and computational algorithms allowed for accurate predictions of properties of the heaviest elements and their experimental behaviour. The works on the relativistic electronic structure calculations for the heaviest elements are overviewed. Preference is given to those related to the experimental research. Role of relativistic effects is discussed.

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H. Lagally

Papers

Ion exchange in aqueous and in aqueous-organic solvents