Microfluidic supported liquid membrane extraction is a promising technique for microliter-scale radionuclide separations because it requires very small reagent volumes and combines extraction and stripping in a single unit operation. Flat sheet supported liquid membrane (FS-SLM) modules with 100, 200, 300, and 400 μm deep channels were fabricated at a cost of less than 5 USD in material using a commercially available resin three-dimensional (3D) printer. The performance of these modules was characterized by quantifying uranium transport across a 15 v/v % tributyl phosphate (TBP) liquid membrane at flow rates between 5 and 60 μL min −1 and developing a two-dimensional (2D) numerical transport model for the system. The extent of uranium extraction was found to increase with increasing residence time and decreasing channel depth, with quantitative extraction occurring at the slowest flow rates and shallowest channel depths. The numerical model agreed well with the experimental extraction results. Time-dependent calculations showed that the modules reach steady state in fewer than 9 min and that there is a considerable buildup of uranium in the membrane during that time.
An intercomparison of the radio-chronometric ages of four distinct plutonium-certified reference materials varying in chemical form, isotopic composition, and period of production are presented. The cross-comparison of the different 234 U/ 238 Pu, 235 U/ 239 Pu, 236 U/ 240 Pu, and 241 Am/ 241 Pu model purification ages obtained at four independent analytical facilities covering a range of laboratory environments from bulk sample processing to clean facilities dedicated to nuclear forensic investigation of environmental samples enables a true assessment of the state-of-practice in "age dating capabilities" for nuclear materials. The analytical techniques evaluated used modern mass spectrometer instrumentation including thermal ionization mass spectrometers and inductively coupled plasma mass spectrometers for isotopic abundance measurements. Both multicollector and single collector instruments were utilized to generate the data presented here. Consensus values established in this study make it possible to use these isotopic standards as quality control standards for radio-chronometry applications. Results highlight the need for plutonium isotopic standards that are certified for 234 U/ 238 Pu, 235 U/ 239 Pu, 236 U/ 240 Pu, and 241 Am/ 241 Pu model purification ages as well as other multigenerational radio-chronometers such as 237 Np/ 241 Pu. Due to the capabilities of modern analytical instrumentation, analytical laboratories that focus on trace level analyses can obtain model ages with marginally larger uncertainties than laboratories that handle bulk samples. When isotope ratio measurement techniques like thermal ionization mass spectrometry and inductively coupled plasma mass spectrometry with comparable precision are utilized, model purification ages with similar uncertainties are obtained.
Rationale
The microanalytical community has an outstanding need for platinum group element (PGE) reference materials, particularly for trace element analysis by laser ablation inductively coupled plasma mass spectrometry (LA‐ICPMS). National Institute of Standards and Technology (NIST) glasses contain Rh, Pd, and Pt, but lack Ru, Os, and Ir. Synthesis of silicate PGE standards has proven difficult due the tendency of PGEs to form metallic nuggets.
Methods
Additive manufacturing methods were used to produce PGE standards with a silica matrix. Monodispersed submicron PGE‐doped Stöber particles were used as feedstock materials for electrophoretic deposition (EPD). Two‐cm‐sized samples produced by EPD were subsequently densified by thermal processing. The homogeneity of PGEs was tested using LA‐ICPMS and concentrations were measured by laser ablation and solution ICPMS.
Results
The PGE concentrations ranged from 0.5 to 3 μg/g. The inhomogeneity was at the 3% RSD level for Ru, Rh, Ir, and Os throughout and 5% for Pt and Pd in the interior of the samples. Based on LA‐ICPMS analyses, the interiors of the two samples have near identical concentrations in PGEs.
Conclusions
The samples fabricated in this study represent the most complete and homogeneous PGE standards produced with a silicate matrix. The ability to produce multiple samples with the same composition provides opportunities for validating methods, monitoring long‐term reproducibility, and facilitating interlaboratory comparisons.
Pu is separated from excess U and isotopically assayed using our novel microfluidic platform designed to miniaturize traditional laboratory techniques into a field-deployable system for rapid nuclear forensics in post-detonation nuclear scenarios.
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