Advancement of isotope separation for the production of reference standards

Abstract

Idaho National Laboratory (INL) operates a mass separator that is currently producing high purity isotopes for use as internal standards for high precision isotope dilution mass spectrometry (IDMS). In 2008, INL began the revival of the vintage 1970s era instrument. Advancements thus far include the successful upgrading and development of system components such as the vacuum system, power supplies, ion-producing components, and beam detection equipment. Progress has been made in the separation and collection of isotopic species including those of Ar, Kr, Xe, Sr, and Ba. Particular focuses on ion source improvements and developments have proven successful with demonstrated output beam currents of over 10 lA 138 Ba and 350 nA 134 Ba from a natural abundance Ba source charge (*2.4 % 134 Ba). In order to increase production and collection of relatively high quantities (mg levels) of pure isotopes, several improvements have been made in ion source designs, source material introduction, and ion detection and collection. These improvements have produced isotopes of high purity ([98 %) and in quantities in the tens of micrograms per run. The instrument and results for pure isotope production for IDMS standards will be presented.

Production of highly-enriched 134Ba for a reference material for isotope dilution mass spectrometry measurements

“…The stable isotope mass separator at INL, previously described in detail by Carney [2], was utilized for all of the isotope separation and collection described here. For the production of near mono-isotopic Ba, a starting material of approximately 1 g metallic, natural Ba is loaded into a hot cathode-type ion source; a modified model q-100 provided by Beam Imaging Solutions Inc. (previously Colutron Research Inc.).…”

“…Fig. 1 Collection blocks mounted behind slits (left) and collection foils made for the slits (right) 2 The instrument limit of quantification was 15 times the standard deviation of the blank divided by the slope of the calibrated instrument response for that specific isotope. The method limit of detection incorporated appropriate dilution factors that were run.…”

“…It is possible with proper spike solutions to obtain elemental measurements of unknown species with uncertainties below 1 % if the spike is well characterized and has stated uncertainties. For the analysis of Ba, there are 134 Ba spike solutions available from Isoflex USA and Oak Ridge National Laboratory Isotopes Division, but their products are enriched to 88.1 ± 0.4 and 84 %, respectively, and have 12-16 % concentrations of 135 Ba, 136 Ba, 137 Ba, and 138 Ba that have nominally stated abundances [2].…”

“…To address the need for more isotopically enriched reference materials, Idaho National Laboratory (INL) is currently operating a 90°sector 1.5 m radius electromagnetic isotope separator that is capable of separating all of the natural Ba isotopes to levels at or above 99 % purity [2]. Producing isotopically enriched solutions from the separated isotopes is difficult however, due to the ease with which samples can be contaminated with natural Ba during the process of harvesting and processing the enriched isotopes.…”

The production of ultra-high purity single isotopes or tailored isotope mixtures by ICP-MS

“…In the following decades, mass spectrometry was entirely displaced for bulk U enrichment in favor of more efficient gaseous diffusion [3] and gas centrifuge [4] technologies, but has remained in use on a small scale using "Calutron" type instruments for the production of enriched isotopes of other elements excluding U on the mg-g-kg scale. Relatively few of these instruments are in routine operation so access to the isotopically enriched product of this type of mass spectrometer (MS) is restricted; principally owing to their large size and the limited market for enriched isotopes that remains mostly research based [5,6]. To produce single isotopes on the gram scale requires the use of high ion currents, typically A-mA, and relatively high operating pressures, ≈1×10 −5 mbar.…”