Separation of no-carrier-added 52Mn from bulk chromium: a simulation study for accelerator mass spectrometry measurement of 53Mn

53Mn radionuclide (T(1/2) = 3.7 x 10(6) y) is produced through the interaction of cosmic rays. Measurements of concentrations of 53Mn in rocks might help to understand Earth surface processes that occurred in time periods not accessible with other cosmogenic nuclides. Only accelerator mass spectrometry (AMS) can determine such ultratrace levels of 53Mn. The main interference in the detection of 53Mn by AMS is its stable isobar 53Cr, which is roughly approximately 10(12) times more abundant in nature. A prerequisite of any AMS measurement of 53Mn in geological samples is therefore chromium separation by an efficient chemistry. Thus, we have developed a method for the separation of chromium and manganese by using a radiometric simulation. The separation procedure was monitored by 51Cr (T(1/2) = 27.70 d) and 52Mn (T(1/2) = 5.59 d) as the corresponding radiotracers for chromium and manganese, respectively. The separation studies were performed by a liquid-liquid extraction technique using trioctylamine (TOA) diluted in cyclohexane. A high separation factor (approximately 16 000) for Mn and Cr can be obtained at optimal conditions of 0.8 M TOA and 9 M HCl. The developed method has been found equally applicable for real geological samples such as manganese crusts, lava, and sediment samples. Therefore, the method offers an important tool to improve 53Mn measurements by AMS.     

Separation of hafnium and zirconium from ti- and fe-rich geological materials by extraction chromatography

This paper presents a new chemical separation method for Hf and Zr from rocks using extraction chromatographic resins prepared from inert polymeric supports and the liquid anionic exchangers tri-n-octylamine or trioctylmethylammonium chloride (Aliquat 336). The method was developed using basaltic and trachyandesitic rocks with high contents of Al, Fe, and Ti. A 100-mg rock sample was decomposed with HF-HNO(3)-HClO(4) and fumed with HClO(4). The residue of this process was dissolved in 10 M HCl and then loaded on the column (6 mm i.d. × 75 mm). The major elements (Al, Ca, Mg, Ti, etc.) were eluted with 10 mL of 10 M HCl, and then Hf, Zr, and Fe were eluted sequentially using 20 mL of 8 M HCl, 20 mL of 2 M HCl, and 5 mL of 1 M HNO(3). The removal efficiency of major elements (Al, Fe, Ca, Mg) was greater than 99% and that of Ti was greater than 95%. The recoveries of Hf and Zr were better than 90% and the Zr/Hf ratio decreased from the natural ratio of 45 in the rock sample to 0.3 in the Hf fraction. This method provides an alternative to the less straightforward procedures based on several stages of ion-exchange separation and might be used for sample preparation prior to (176)Hf/(177)Hf determinations by magnetic sector multicollection ICPMS.     

Sample preparation for quantitation of tritium by accelerator mass spectrometry

The capability to prepare samples accurately and reproducibly for analysis of tritium (3H) content by accelerator mass spectrometry (AMS) greatly facilitates isotopic tracer studies in which attomole levels of 3H can be measured in milligram-sized samples. A method has been developed to convert the hydrogen of organic samples to a solid, titanium hydride, which can be analyzed by AMS. Using a two-step process, the sample is first oxidized to carbon dioxide and water. In the second step, the water is transferred within a heated manifold into a quartz tube, reduced to hydrogen gas using zinc, and reacted with titanium powder. The 3H/1H ratio of the titanium hydride is measured by AMS and normalized to standards whose ratios were determined by decay counting to calculate the amount of 3H in the original sample. Water, organic compounds, and biological samples with 3H activities measured by liquid scintillation counting were utilized to develop and validate the method. The 3H/1H ratios were quantified in samples that spanned 5 orders of magnitude, from 10(-10) to 10(-15), with a detection limit of 3.0 x 10(-15), which is equivalent to 0.02 dpm tritium/mg of material. Samples smaller than 2 mg were analyzed following addition of 2 mg of a tritium-free-hydrogen carrier. Preparation of organic standards containing both 14C and 3H in 2-mg organic samples demonstrated that this sample preparation methodology can also be applied to quantify both of these isotopes from a single sample.     

A fast response hafnium selective polymeric membrane electrode based on N,N'-bis(alpha-methyl-salicylidene)-dipropylenetriamine as a neutral carrier

In this study a new hafnium selective sensor was fabricated from polyvinylchloride (PVC) matrix membrane containing neutral carrier N,N'-bis(alpha-methyl-salicylidene)-dipropylenetriamine (Mesaldpt) as a new ionophore, sodium tetraphenyl borate (NaTPB) as anionic discriminator and dioctyl phthalate (DOP) as plasticizing solvent mediator in tetrahydrofuran solvent. The electrode exhibits Nernstian response for Hf(4+) (Hafnium(IV)) over a wide concentration range (2.0 x 10(-7) to 1.0 x 10(-1)M) with the determination coefficient of 0.9966 and slope of 15.1+/-0.1 mVdecades(-1). The limit of detection is 1.9 x 10(-7)M. The electrode has a fast response time of 18s and a working pH range of 4-8. The proposed membrane shows excellent discriminating ability towards Hf(4+) ion with regard to several alkali, alkaline earth transition and heavy metal ions. It can be used over a period of 1.5 months with good reproducibility. It is successfully applied for direct determination of Hf(4+) in solutions by standard addition method for real sample analysis.     

Magnetic properties, phase evolution, and microstructure of melt spun Hf-substituted Sm(Co0.97Hf0.03)(x)Cy (x = 5-9; y = 0-0.1) nanocomposites

Magnetic properties, phase evolution, and microstructure of melt spun Hf-substituted Sm(Co0.97Hf0.03)(x)Cy (x = 5-9; y = 0-0.1) ribbons quenched at the wheel speed of 40 m/s are investigated. X-ray diffraction analysis shows that the main phases existed in Sm(Co0.97Hf0.03)(x) ribbons are 1:5 phase for x = 5-5.5; 1:5 and 1:7 phases for x = 6; 1:7 phase for x = 6.5-7.5; 1:7 and 2:17 phases for x = 8; and only 2:17 phase for x = 8.5-9, respectively. For Sm(Co0.97Hf0.03)(x) (x = 5-9) ribbons, the optimum magnetic properties of B(r) = 5.6 kG, (i)H(c)= 15.6 kOe and (BH)(max) = 7.1 MGOe are obtained for Sm(Co0.97Hf0.03)6.5 ribbons. Furthermore, a slight amount of C addition in Sm(Co0.97Hf0.03)(x) ribbons slightly modify phase constitution and effectively refine the grain size from 200-700 nm for C free ribbons to 10-70 nm, strengthening the exchange coupling effect between magnetic grains of the ribbons. As a result, magnetic properties are further improved. The magnetic properties of B(r) = 6.9 kG, (i)H(c) = 9.2 kOe and (BH)(max) = 10.0 MGOe can be achieved for Sm(Co0.97Hf0.03)7.5C0.1 nanocomposites.     

Photocatalytic dehalogenation coupled on-line to a reversed micellar-mediated chemiluminescence detection system: application to the determination of iodinated aromatic compounds

The effects of illumination time, temperature, catalyst concentration, and pH on the on-line photocatalytic dehalogenation of iodinated aromatic compounds in a near-UV-illuminated titanium dioxide (anatase type) aqueous suspension were monitored via the iodine-luminol chemiluminescence (CL) reaction in a reversed micellar medium, and a new, automated, rapid, and efficient method was developed. A water-cooled, 400-W high-pressure Hg lamp was used as an internal light source. The flow procedure involved the following: (1) photocatalytic dehalogenation/degradation of the iodinated compound by the near-UV-illuminated titanium dioxide and the production of iodide species, (2) oxidation of iodide into iodine, (3) extraction of iodine into cyclohexane, (4) membrane separation of the iodine-containing organic phase from the aqueous phase, and (5) the detection of iodine using the luminol CL reaction in the reversed micellar solution of cetyltrimethylammonium chloride in 6:5 (v/v) chloroform-cyclohexane/water buffered with sodium carbonate. Results for the dehalogenation of the iodinated compounds, o-iodobenzoic acid and L-thyroxine (3,5,3',5'-tetraiodothyronine) sodium, were compared with a standard inorganic iodide solution. After establishing the optimum chemical and instrumental conditions, detection limits of 0.8 x 10(-9) and 0.2 x 10(-9) M and linear calibration graphs were obtained with dynamic ranges from 0.79 x 10(-7) to 7.9 x 10(-7) M and from 0.20 x 10(-7) to 2.0 x 10(-7) M for o-iodobenzoic acid and L-thyroxine, respectively. A precision of approximately 4% relative standard deviation (n = 6) was provided at an o-iodobenzoic acid concentration of 0.79 x 10(-7) M. The method developed was applied to the on-line determinations of iodinated aromatic compounds such as L-thyroxine sodium and iopamidol ((S)-N,N'-bis[2-hydroxy-1-(hydroxymethyl)ethyl]-5-[(2-hydroxy-1-oxopropyl)amino]-2,4,6-triiodoisophthaldiamide) in pharmaceuticals.     

An extraction chromatography method for Hf separation prior to isotopic analysis using multiple collection ICP-mass spectrometry

A novel method for the single-step separation of Zr + Hf from all matrix elements of geological samples has been developed for Hf isotopic measurements using multiple collector-ICP-mass spectrometry. The method combines an effective sample decomposition by LiBO2 fusion with a selective separation of Hf + Zr by a solid-phase extraction material based on dipentyl pentyl phosphonate, commercially available as U-TEVA.Spec. Using this simple and rapid procedure, Hf and Zr can be isolated in a single separation step with good recoveries (>90%) and satisfactory blank levels (approximately 55 pg of Hf), so that a subsequent isotopic measurement with ICPMS is possible. An excellent separation from rock-forming constituents is achieved, including those elements (Al, P, Ti, Cr, Fe, Mo, etc.) known to interfere in conventional separation methods based on ion-exchange techniques. The potential of this new method for Hf isotopic analysis is demonstrated by replicate MC-ICPMS measurements of 176Hf/177Hf ratios in seven international reference materials of silicate rocks, spanning a range of Hf contents and bulk compositions.     

Structures and electronic properties of M2C2 @ C78 (M = Ti, Zr, Hf): a density functional theory study

A systematic DFT investigation has been conducted to explore the structures and electronic properties of the metal-carbide endofullerenes M2C2 @ C78 (M = Ti, Zr, Hf) at the PBE/DNP level of theory. The theoretical calculations predicted the following: (i) this series of endofullerenes have the valence states [M4+]2C2(2-) @ C78(6-) (ii) the structure of the [M2C2](6+) cluster encapsulated in the C78(6-) (D3h) cage varies with the increasing of the ionic radius of M4+, i.e., from a linear M-C [triple bond] C-M geometry for M = Ti, through a zigzag geometry for M = Hf to a side-on binding mode for M = Zr; (iii) M2C2 @ C78 (M = Zr, Hf) should display interesting intramolecular dynamic behavior at room temperature, i.e., the encapsulated C2(2-) moiety can rotate freely around the C3-axis of the C78(6-) (D3h) cage; (iv) the [Ti2C2]6+ in the lightest Ti2C2 @ C78 is far more fixed by adopting the linear Ti-C - C-Ti geometry; (v) the order for their ionization potentials is Ti2C2 @ C78 < Hf2C2 @ C78 < Zr2C2 @ C78, whereas their EAs follow the order: Ti2C2 @ C78 < Hf2C2 @ C78 approximately Zr2C2 @ C78. The predicted redox properties of these endofullerenes suggest that Zr2C2 @ C78 is synthetically as approachable as Hf2C2 @ C78.     

Homogeneous immunoassay for detection of TNT and its analogues on a microfabricated capillary electrophoresis chip

A homogeneous immunoassay for TNT and its analogues is developed using a microfabricated capillary electrophoresis chip. The assay is based on the rapid electrophoretic separation of an equilibrated mixture of an anti-TNT antibody, fluorescein-labeled TNT, and unlabeled TNT or its analogue. The band intensities of the free fluorescein-labeled TNT and of the antibody-antigen complex reveal the relative equilibrated concentrations. Titration of the anti-TNT antibody with a fluorescein-labeled TNT derivative yields a binding constant of (3.9 +/- 1.3) x 10(9) M(-1). The dissociation rate constant of the complex is determined by kinetic capillary electrophoresis using a folded channel and a rotary scanner to interrogate the separation at multiple time points. The dissociation rate constant is found to be 0.035 +/- 0.005 s(-1), and the resulting binding rate constant is (1.4 +/- 0.7) x 10(7) M(-1) s(-1). Binding constants of TNT and five of its analogues are determined by competitive assays: TNT (4.3 +/- 2.6) x 10(8) M(-1); 1,3,5-trinitrobenzene (5.1 +/- 3.3) x 10(7) M(-1); picric acid (7.5 +/- 4.4) x 10(6) M(-1); 2,4-dinitrotoluene (7.9 +/- 4.0) x 10(6) M(-1); 1,3-dinitrobenzene (1.0 +/- 0.7) x 10(6) M(-1); and 2,4-dinitrophenol (5.1 +/- 3.0) x 10(4) M(-1). TNT and its analogues can be assayed with high sensitivity (LOD 1 ng/mL) and with a wide dynamic range (1-300 ng/mL) using this chip-based method.     

A wireless electrochemiluminescence detector applied to direct and indirect detection for electrophoresis on a microfabricated glass device

A novel electrochemiluminescence (ECL) detector is presented in this article. The detector is applied for micellar electrokinetic chromatographic separation of dichlorotris(2,2'-bipyridyl)ruthenium(II) hydrate [Ru-(bpy)] and dichlorotris(1,10-phenanthroline)ruthenium-(II) hydrate [Ru(phen)] on a microfabricated glass device. It consists of a microfabricated "U"-shape floating platinum electrode placed across the separation channel. The legs of the U function respectively as working and counter electrode. The required potential difference for the ECL reaction is generated at the Pt electrode by the electric field available in the separation channel during electrophoretic separation. Initial experiments demonstrate a micellar electrokinetic separation and direct ECL detection of 10(-16) mol of Ru(phen) (10(-6) M) and 4.5 x 10(-16) mol of Ru(bpy) (5 x 10(-6) M). Also, preliminary results show the indirect detection of three amino acids. The high voltage at the location of detection does not interfere with the electrochemistry.     

Characterization of low losses in optical thin films and materials

Residual absorption in optical coatings and materials is directly measured by means of the laser-induced deflection (LID) technique. For transmissive coatings a measurement strategy is introduced that allows for the separation of different absorptions of the investigated sample (bulk, coating, surface) by use of only one sample. Laser irradiation yields absorption values between 2 x 10(-3) and 2.9 x 10(-2) for antireflecting and highly reflecting (HR) coatings at 193 nm and 30.6 x 10(-6) for a HR mirror at 527 nm. Use of laser-induced fluorescence at 193 nm excitation reveals trivalent cerium and prasodymium and hydrocarbons in different single layers and coatings. In addition to correlation with absorption data, the influence of a high fluorescence quantum yield on the absorption measurement is discussed.     

Extraction of phenol by sulfuric acid salts of trioctylamine

Abstract

The extraction of phenol from an aqueous solution using sulfuric acid salts of trioctylamine (TOA salts) was carried out. Trioctylamine (TOA) dissolved in diisopropyl ether (DIPE) (or 1‐octanol, cyclohex‐ane, benzene and kerosene) was evaluated for extraction of phenol at various volume ratios of organic phase to aqueous phase at varied temperatures. The equilibrium distribution coefficient (K_D ) for the extraction of phenol with TOA salts in those diluents was measured. Phenol is extracted by a physical distribution with pure diluent alone and through the interaction between TOA and phenol. The latter was quantitatively interpreted according to a reaction scheme in which adducts of several kinds were composed of trioctylamine and phenol. The TOA salts have a significantly greater extraction capability for phenol than TOA itself. The reaction of phenol and hydroxide ion to form phenoxide ion is used to explain the small extraction of solute at high pH. A simple mathematical model was derived to account for the effect of the volume ratio of organic phase to aqueous phase on the value of K_D, and for the effect of the initial concentration of phenol on the value of K_D.     

Elemental analysis of organic species with electron ionization high-resolution mass spectrometry

We present a new elemental analysis (EA) technique for organic species (CHNO) that allows fast on-line analysis (10 s) and reduces the required sample size to approximately 1 ng, approximately 6 orders of magnitude less than standard techniques. The composition of the analyzed samples is approximated by the average elemental composition of the ions from high-resolution electron ionization (EI) mass spectra. EA of organic species can be performed on organic/inorganic mixtures. Elemental ratios for the total organic mass, such as oxygen/carbon (O/C), hydrogen/carbon (H/C), and nitrogen/carbon (N/C), in addition to the organic mass to organic carbon ratio (OM/OC), can be determined. As deviations between the molecular and the ionic composition can appear due to chemical influences on the ion fragmentation processes, the method was evaluated and calibrated using spectra from 20 compounds from the NIST database and from 35 laboratory standards sampled with the high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The analysis of AMS (NIST) spectra indicates that quantification of O/C is possible with an error (average absolute value of the relative error) of 30% (17%) for individual species. Precision is much better than accuracy at +/-5% in the absence of air for AMS data. AMS OM/OC has an average error of 5%. Additional calibration is recommended for types of species very different from those analyzed here. EA was applied to organic mixtures and ambient aerosols (sampled at 20 s from aircraft). The technique is also applicable to other EI-HRMS measurements such as direct injection MS.     

Potentiometric detection of carboxylic acids, phosphate esters, and nucleotides in liquid chromatography using anion-selective coated-wire electrodes

An all-solid-state ion-selective membrane electrode incorporating a lipophilic anion exchanger was used in a flow-through potentiometric detector for the LC determination of organic anions of biological interest. Different metabolic intermediates (mono-, di-. and tricarboxylic acids, sugar phosphates, and nucleotides) were detected sensitively after separation on a pellicular anion-exchange chromatographic column. The electrode was coated by directly casting the electroactive mixture on a glassy carbon support of 3 mm diameter and used in a wall-jet-type flow cell. The analysis conditions were optimized to obtain both efficient separation and sensitive detection. Calibration curves showed a logarithmic dependence on the injected concentration for concentrations higher than 5.0 x 10(-5) M and a linear dependence for injected concentrations below this value. Under isocratic conditions, detection limits of 5.0 x 10(-7) M (25 pmol) were attained when a sodium hydroxide solution was used as an eluent. No suppressor system was needed in this case. The relative standard deviation for consecutive injections was 0.3% (n = 15), and the electrode lifetime was at least 2 months. The utility of potentiometric detection is further demonstrated in a gradient elution separation for single-run analysis of a synthetic mixture of biochemical compounds containing carboxylic acids, phosphate esters, and nucleotides.     

A fiber-optic fluorescence sensor for lithium ion in acetonitrile

A novel fiber-optic fluorescence sensor based on a controlled-release reagent for the determination of lithium ion in organic solvents is proposed. The fluorogenic indicator 2-(2-hydroxyphenyl)benzoxazole is contained in a mini-polyethylene tube as the reagent reservoir and is brought into contact with the analyte solution by diffusion across a poly(vinyl chloride) (PVC) membrane to form a strongly fluorescent complex at the membrane/solution interface. The fluorescence signals produced are measured via two joined optical fibers positioned closely to the backside of the PVC membrane for light illumination and collection. The sensor is useful for measuring Li+ at concentrations in acetonitrile ranging from 1.0 x 10(-6) to 1.0 x 10(-2) M with a detection limit of 3.0 x 10(-7) M. The steady-state response can be reached within seconds, and the signal changes are fully reversible. The sensor shows minimal interference effects from other alkali metal and alkaline earth metal cations and has good stability and durability when stored in acetonitrile solutions.     

Investigation of factors that affect the sensitivity of accelerator mass spectrometry for cosmogenic 10Be and 26Al isotope analysis

We report experiments designed to improve accelerator mass spectrometry (AMS) of (10)Be and (26)Al for a wide range of geological applications. In many cases, the precision of the AMS isotope ratio measurement is restricted by counting statistics for the cosmogenic isotope, which are in turn limited by the intensity of AMS stable ion beam currents. We present data obtained at the Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermore National Laboratories (LLNL) indicating that AMS ion beam currents are impacted by certain elemental impurities. For (10)Be analysis, the AMS ion beam current is most adversely affected by the presence of titanium (which can be challenging to separate chemically during sample preparation because of its tendency toward stable refractory forms) and aluminum (which can coelute with beryllium during cation exchange chromatography). In order to minimize impurities that suppress AMS ion beam currents, we evaluate, using inductively coupled plasma atomic emission spectroscopy (ICP-AES), a widely used chemical separation protocol involving a multiacid digestion scheme, preseparation elemental analysis, anion exchange chromatography, ad hoc selective precipitation, cation exchange chromatography, and postseparation elemental analysis.     

Extraction and recovery of methylene blue from industrial wastewater using benzoic acid as an extractant

Liquid-liquid extraction (LLE) of methylene blue (MB) from industrial wastewater using benzoic acid (extractant) in xylene has been studied at 27 degrees C. The extraction of the dye increased with increasing extractant concentration. The extraction abilities have been studied on benzoic acid concentration in the range of 0.36-5.8x10(-2) M. The distribution ratio of the dye is reasonably high (D=49.5) even in the presence of inorganic salts. Irrespective of the concentration of dye, extraction under optimal conditions was 90-99% after 15 min of phase separation. The extracted dye in the organic phase can be back extracted into sulphuric acid solution. The resultant recovered organic phase can be reused in succeeding extraction of dye with the yield ranging from 99 to 87% after 15 times reused, depending on the concentration of the initial feed solution. Experimental parameters examined were benzoic acid concentration, effect of diluent, effect of pH, effect of initial dye concentration, effect of equilibration time, various stripping agents, aqueous to organic phase ratio in extraction, organic to aqueous phase ratio in stripping and reusability of solvent.     

Study of Extraction of Palladium from Nitric Acid Solutions with Nitrogen-Containing Compounds,as Applied to Recovery of Fission Palladium from Spent Nuclear Fuel of Nuclear Power Plants: 2. Effect of Radiation on Palladium Recovery and Condition of Extraction Systems

Extraction of palladium nitrate complexes from 1-3 M HNO₃ with tri-n-octylamine (TOA) and tricaprylmethylammonium nitrate (Aliquat 336 nitrate) in diethylbenzene under irradiation at a dose of up to 100 W h l^{- 1} is studied. In irradiated extraction systems, the acidity of the aqueous and organic phases decreases and HNO₂ is formed. With increasing radiation dose the degree of Pd recovery decreases by virtue of partial degradation of the organic phase. The radiation effects on the condition of extraction systems are discussed.     

An antibody-immobilized capillary column as a bioseparator/bioreactor for detection of Escherichia coil O157:H7 with absorbance measurement.

A capillary-column-based bioseparator/bioreactor was developed for detection of Escherichia coli O157:H7 by chemically immobilizing anti-E. coli O157:H7 antibodies onto the inner wall of the column, forming the "sandwich" immunocomplexes (immobilized antibody-E. coli O157: H7-enzyme-labeled antibody) after the sample and the enzyme-labeled antibody passed through the column and detecting the absorbance of the product in the bioreactor with an optical detector. The effects of the blocking agent, flow rate of samples and substrates, buffer, MgCl2, and pH on the detection of E. coli O157:H7 were investigated. The parameters, 2% BSA in 1.0 x 10-2 M, pH 7.4, PBS as the blocking agent, 0.5 mL/h as the sample flow rate, 1.0 x 10(-2) M MgCl2, and 2.0 x 10(-4) M p-nitrophenyl phosphate in 1.0 M, pH 9.0 Tris buffer as the substrate for the enzymatic reaction, and 1.0 mL/h as the substrate flow rate, were used in the bioseparator/bioreactor system for detection of E. coli O157:H7. The selectivity of the system was checked, and other pathogens, including Salmonella typhimurium, Campylobacterjejuni, and Listeria monocytogenes, had no interference with the detection of E. coli O157:H7. Its working range was from 5.0 x 10(2) to 5.0 x 10(6) cfu/mL, and the total assay time was < 1.5 h without any enrichment. The relative standard deviation was approximately 2.0-7.3%.     

Separation of Am and Cm by Extraction from Weakly Acidic Nitrate Solutions with Tributyl Phosphate in Isoparaffin Diluent

Trivalent transplutonium (TPE) and rare earth (REE) elements are extracted to more than 80% with 30% TBP in Isopar M from solutions containing 0.06–0.5 M HNO₃ and a salting-out agent, NH₄NO₃, in a concentration of ≥6 M. The elements are stripped from the organic phase with 0.1 M HNO₃. The Am(III)/Eu separation factors vary from 1.8 to 2, which can be used for their extraction separation. The Cm/Am(III) separation factors in 0.06–3 M HNO₃ are in the range from 1.1 to 1.2; therefore, to separate these elements, higher oxidation states of Am, Am(VI) and Am(V), should be used. The effect of various factors on the stability of Am(VI) was examined, and the conditions of the existence of Am(VI) and Am(V) in ≤0.1 M HNO3 solutions containing ~8 M NH₄NO₃ were determined. Curium is extracted with 30% TBP in Isopar M virtually completely, whereas americium only partially (≤30%) passes into the organic phase in the form of Am(III). In the process, high degree of separation of Cm from Am(V) remaining in the aqueous phase is reached (≥99.9%).