A review on the mass spectrometric studies of americium: Present status and future perspective

Determination of ultra-trace level 241Am in marine sediment and seawater by combining TK200-TK221 tandem-column extraction chromatography and SF ICP-MS

Sound strategies for marine chemical monitoring call for measurement systems capable of producing comparable analytical results with demonstrated quality. This work presents the development and validation of a new analytical procedure for the determination of the 241Am mass fraction in marine sediment and seawater samples at low levels. The procedure includes a tandem-column extraction chromatography for separation of 241Am and sector field-inductively coupled plasma mass spectrometry (SF ICP-MS) for its determination. The separation is based on the application of two new extraction resins, TK200 and TK221. The acid leaching method was employed for the pre-treatment of marine sediments, while Fe(OH)3 co-precipitation was used for Am pre-concentration in seawater samples. The extraction behaviors of Am on TK221 resins in the different acidic mediums were investigated. The removal capabilities of the tandem TK200-TK221 columns for the 241Am in the presence of interfering elements including Pu, Pb, Hg, Bi, Tl, Pt, Hf, U, and Th were carefully investigated and the corresponding decontamination factors (DFs) estimated to be in the range from 104 to 106. The main interfering element Pu was efficiently removed with a DF of about 6 × 105. Matrix rare earth elements (REEs) in marine sediments were further removed by the application of TEVA resins. 241Am mass fraction was quantified by the application of external calibration and SF ICP-MS. Following the recommendations of the ISO/IEC 17025 guidelines, the validation of the analytical procedure was accomplished by executing it on the certified reference material (CRM) IAEA-385 (marine sediment) and the seawater IAEA-443 reference materials (RM). The obtained results showed that 241Am mass fractions were accurately determined in both reference samples, with excellent reproducibility (2.1 % and 7.6 %) and low LODs (0.4 fg g-1 and 0.2 fg g-1). The relative expanded uncertainties (k = 2) obtained were 17.1 % and 29.0 %, respectively. The overall analytical times for the application of the proposed procedure on the marine sediment and seawater samples were evaluated to be only about 9 h and 6.5 h, respectively. It shows great advantages for its potential applications for emergency monitoring of 241Am contamination in the marine environment.

Removal of 241Am from Aqueous Solutions by Adsorption on Sponge Gourd Biochar

Luffa cylindrica biomass was converted to biochar and the removal of 241Am by pristine and oxidized biochar fibers was investigated in laboratory and environmental water samples. This species has the added advantage of a unique microsponge structure that is beneficial for the production of porous adsorbents. The main purpose of this study was to valorize this biomass to produce an efficient adsorbent and investigate its performance in radionuclide-contaminated waters. Following the preparation of Am3+ solutions at a concentration of 10−12 mol/L, the adsorption efficiency (Kd) was determined as a function of pH, adsorbent mass, ionic strength, temperature, and type of aqueous solution by batch experiments. At the optimum adsorbent dose of 0.1 g and pH value of 4, a log10Kd value of 4.2 was achieved by the oxidized biochar sample. The effect of temperature and ionic strength indicated that adsorption is an endothermic and entropy-driven process (ΔH° = −512 kJ mol−1 and ΔS° = −1.2 J K−1 mol−1) leading to the formation of inner-sphere complexes. The adsorption kinetics were relatively slow (24 h equilibrium time) due to the slow diffusion of the radionuclide to the biochar surface and fitted well to the pseudo-first-order kinetic model. Oxidized biochar performed better compared to the unmodified sample and overall appears to be an efficient adsorbent for the treatment of 241Am-contaminated waters, even at ultra-trace concentrations.

Determination of 241Am in Environmental Samples: A Review

The determination of ²⁴¹Am in the environment is of importance in monitoring its release and assessing its environmental impact and radiological risk. This paper aims to give an overview about the recent developments and the state-of-art analytical methods for ²⁴¹Am determination in environmental samples. Thorough discussions are given in this paper covering a wide range of aspects, including sample pre-treatment and pre-concentration methods, chemical separation techniques, source preparation, radiometric and mass spectrometric measurement techniques, speciation analyses, and tracer applications. The paper focuses on some hyphenated separation methods based on different chromatographic resins, which have been developed to achieve high analytical efficiency and sample throughput for the determination of ²⁴¹Am. The performances of different radiometric and mass spectrometric measurement techniques for ²⁴¹Am are evaluated and compared. Tracer applications of ²⁴¹Am in the environment, including speciation analyses of ²⁴¹Am, and applications in nuclear forensics are also discussed.

An efficient method for the removal of Pb prior to the ultra-trace Am measurement by ICP-MS

The existence of Pb which formed polyatomic ions such as PbCl+, PbAr+ would interfere the determination of ultra-trace Am by ICP-MS. An extraction chromatography method for the removal of Pb interference was provided in this work to improve the determination accuracy of ultra-trace Am by ICP-MS. In this study, Sr resin was applied to separate Am and Pb because of the great difference between Am and Pb on adsorption ability. The variable parameters including nitric acid concentration, loading volume, column height and loading amount were investigated to optimize the separation conditions for high recovery of Am (R(Am)) as well as high decontamination factor of Pb (DF(Pb)). The optimal separation method was recommended in the study with the recovery of Am over 99% and the decontamination factor of Pb over 2 × 105. Moreover, the method was successfully applied to the analysis of 241Am in the simulated samples.

Separation of Americium from Curium through Oxidation State Control with Record Efficiency

Separation of americium (Am) from curium (Cm) could greatly facilitate the development of advanced nuclear fuel cycles, help with accurate nuclear forensic analysis, and allow for more efficient recovery and utilization of the two strategic elements. In this work, an Am/Cm separation strategy based on the stabilization of pentavalent Am in a biphasic solvent extraction system using bismuthate as the oxidant and N,N,N',N'-tetraoctyl diglycolamide (TODGA) as the extractant was developed. The distinctive differences between Am(V) and Cm(III) in terms of both steric configuration and charge density afford record high Cm/Am separation factors (>10⁴) through only one single contact in solvent extraction. This separation strategy possesses superior features including fast kinetics, long-time stability, no secondary solid radioactive waste generation, and applicability over a wide range of HNO₃ acidities, making it promising for Am/Cm separation and analysis in a variety of applications.

243Am certified reference material for mass spectrometry

The Joint Research Centre, in cooperation with the Commissariat à l’Energie Atomique et aux Energies Alternatives, produced a novel 243Am spike reference material for mass spectrometry. Americium solution with an isotopic composition of 88% 243Am and 12% 241Am was used as the source for the preparation of the spike material. The certified value of 5.696 (11) nmol g−1 for the amount content of 243Am and 0.136138 (54) for the n(241Am)/n(243Am) amount ratio were assigned. The assigned values from mass spectrometry were confirmed by alpha-particle spectrometry, alpha-particle counting at a defined solid angle, and high-resolution gamma-ray spectrometry. Furthermore, an external validation of the certified values was obtained from the results of an interlaboratory comparison exercise, using this americium reference solution as the test sample.

Exploring the Coordination of Plutonium and Mixed Plutonyl-Uranyl Complexes of Imidodiphosphinates

The coordination chemistry of plutonium(IV) and plutonium(VI) with the complexing agents tetraphenyl and tetra-isopropyl imidodiphosphinate (TPIP^- and TIPIP^-) is reported. Treatment of sodium tetraphenylimidodiphosphinate (NaTPIP) and its related counterpart with peripheral isopropyl groups (NaTIPIP) with [NBu₄]₂[Pu^IV(NO₃)₆] yields the respective Pu^IV complexes [Pu(TPIP)₃(NO₃)] and [Pu(TIPIP)₂(NO₃)₂] + [Pu^IV(TIPIP)₃(NO₃)]. Similarly, the reactions of NaTPIP and NaTIPIP with a Pu(VI) nitrate solution lead to the formation of [PuO₂(HTIPIP)₂(H₂O)][NO₃]₂, which incorporates a protonated bidentate TIPIP^- ligand, and [PuO₂(TPIP)(HTPIP)(NO₃)], where the protonated HTPIP ligand is bound in a monodentate fashion. Finally, a mixed U(VI)/Pu(VI) compound, [(UO₂/PuO₂)(TPIP)(HTPIP)(NO₃)], is reported. All these actinyl complexes remain in the +VI oxidation state in solution over several weeks. The resultant complexes have been characterized using a combination of X-ray structural studies, NMR, optical, vibrational spectroscopies, and electrospray ionization mass spectrometry. The influence of the R-group (R = phenyl or ⁱPr) on the nature of the complex is discussed with the help of DFT studies.