Impact of sulfate on the solubility of Tc(IV) in acidic to hyperalkaline aqueous reducing systems

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sarah B. Duckworth ◽  
Xavier Gaona ◽  
Alexander Baumann ◽  
Kathy Dardenne ◽  
Jörg Rothe ◽  
...  
Keyword(s):  
Solid Phase ◽  
Correction Factors ◽  
Mixed Salt ◽  
Ph Values ◽  
Reducing Conditions ◽  
Upper Limits ◽  
Salt Systems ◽  
Amorphous Character ◽  
Good Agreement

Abstract The solubility of 99Tc(IV) was investigated from undersaturation conditions in NaCl–Na2SO4 (0.3 M ≤ I ≤ 5.0 M), MgCl2–MgSO4 (I = 13.5 M) and CaCl2–CaSO4 (I = 13.5 M) systems with 0.001 M ≤ [SO4 2−]tot ≤ 1.0 M and 1 ≤ pH m  ≤ 12 (with pH m  = −log[H+], in molal units). Reducing conditions were set by either Sn(II) or Fe(0). Special efforts were dedicated to accurately characterize the correction factors A m required for the determination of pH m from the experimentally measured pH values in the mixed salt systems investigated, with pH m  = pHexp + A m . The combination of (pe + pH m ) measurements with Pourbaix diagrams of Tc suggests that technetium is present in its +IV redox state. This hypothesis is confirmed by XANES, which unambiguously shows the predominance of Tc(IV) both in the aqueous and solid phases of selected solubility samples. XRD and SEM–EDS support the amorphous character of the solid phase controlling the solubility of Tc(IV). EXAFS data confirm the predominance of TcO2(am, hyd) at pH m  > 1.5, whereas the formation of a Tc(IV)–O–Cl solid phase is hinted at lower pHm values in concentrated NaCl–Na2SO4 systems with ≈5 M NaCl. Solubility data collected in sulfate-containing systems are generally in good agreement with previous solubility studies conducted in sulfate-free NaCl, MgCl2 and CaCl2 solutions of analogous ionic strength. Although the complexation of Tc(IV) with sulfate cannot be completely ruled out, these results strongly support that, if occurring, complexation must be weak and has no significant impact on the solubility of Tc(IV) in dilute up to highly saline media. Solubility upper-limits determined in this work can be used for source term estimations including the effect of sulfate in a variety of geochemical conditions relevant in the context of nuclear waste disposal.

Energy Losses at Tees With Large Area Ratios

2005 ◽  
Vol 127 (1) ◽  
pp. 110-116 ◽  
Author(s):  
Kenji Oka ◽  
Hidesato Ito¯
Keyword(s):  
Branch Pipe ◽  
Circular Cross Section ◽  
Correction Factors ◽  
Large Area ◽  
Combined Flow ◽  
Flow Through ◽  
Loss Coefficients ◽  
Energy And Momentum ◽  
Good Agreement

The loss coefficients for smooth, sharp-edged tees of circular cross-section with the area ratio of 11.44 were determined experimentally for five branch angles which ranged from 45 deg to 135 deg giving special consideration to all configurations of flow through the tees. The Reynolds number, in the leg carrying the combined flow, was kept to a constant value, i.e., 105 for the branch pipe and 3×104 for the main pipe, respectively. The equations for loss coefficients developed from the continuity, energy, and momentum principles give good agreement with the experimental results for tees with large area ratios provided that correction factors are introduced. The correction factors were determined by the analysis of the experimental data with the relative uncertainties from 0.9 to 3.3% according to the configurations of flow. The results constitute a useful guide to the determination of the loss coefficients for tees with large area ratios.

Magnetizable solid-phase fluoroimmunoassay of thyroxine by a sequential addition technique.

1980 ◽  
Vol 26 (12) ◽  
pp. 1701-1703 ◽  
Author(s):  
R D Nargessi ◽  
J Ackland ◽  
M Hassan ◽  
G C Forrest ◽  
D S Smith ◽  
...  
Keyword(s):  
Solid Phase ◽  
Free Fraction ◽  
Iron Oxide Particles ◽  
Correlation Studies ◽  
Endogenous Fluorophores ◽  
Sequential Addition ◽  
Oxide Particles ◽  
Covalently Linked ◽  
Good Agreement

Abstract We describe a simple fluoroimmunoassay for the determination of thyroxine concentrations in serum. The method, "sequential addition, separation fluoroimmunoassay," involves both thyroxine labeled with fluorescein and magnetizable cellulose/iron oxide particles to which antibodies to thyroxine have been covalently linked. Serum sample or standard is incubated with an excess of the solid-phase antibody; the particles, which now carry most of the antigen in the sample, are sedimented onto a magnet and the supernate, which contains endogenous fluorophores and other interfering factors, is removed and discarded. Excess labeled thyroxine is then added, and, after incubation, the fluorescence in the supernate (free fraction), which is related directly to the amount of thyroxine in the sample is measured. For the whole procedure, including fluorometry, each sample is treated entirely within disposable polystyrene test tubes. Correlation studies with two different radioimmunoassays showed good agreement.

scholarly journals Confronting expansion distances of planetary nebulae with Gaia DR2 measurements

2019 ◽  
Vol 625 ◽  
pp. A137 ◽  
Author(s):  
D. Schönberner ◽  
M. Steffen
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Precise Determination ◽  
Asymptotic Giant Branch ◽  
Correction Factors ◽  
Trigonometric Parallaxes ◽  
Formation And Evolution ◽  
Hydrodynamical Simulations ◽  
Good Agreement

Context. Individual distances to planetary nebulae are of the utmost relevance for our understanding of post-asymptotic giant-branch evolution because they allow a precise determination of stellar and nebular properties. Also, objects with individual distances serve as calibrators for the so-called statistical distances based on secondary nebular properties. Aims. With independently known distances, it is possible to check empirically our understanding of the formation and evolution of planetary nebulae as suggested by existing hydrodynamical simulations. Methods. We compared the expansion parallaxes that have recently been determined for a number of planetary nebulae with the trigonometric parallaxes provided by the Gaia Data Release 2. Results. Except for two out of 11 nebulae, we found good agreement between the expansion and the Gaia trigonometric parallaxes without any systematic trend with distance. Therefore, the Gaia measurements also prove that the correction factors necessary to convert proper motions of shocks into Doppler velocities cannot be ignored. Rather, the size of these correction factors and their evolution with time as predicted by 1D hydrodynamical models of planetary nebulae is basically validated. These correction factors are generally greater than unity and are different for the outer shell and the inner bright rim of a planetary nebula. The Gaia measurements also confirm earlier findings that spectroscopic methods often lead to an overestimation of the distance. They also show that even modelling of the entire system of star and nebula by means of sophisticated photoionisation modelling may not always provide reliable results. Conclusions. The Gaia measurements confirm the basic correctness of the present radiation-hydrodynamics models, which predict that both the shell and the rim of a planetary nebula are two independently expanding entities, created and driven by different physical processes, namely thermal pressure (shell) or wind interaction (rim), both of which vary differently with time.

Solubility of Niobium(V) under Cementitious Conditions: Importance of Ca-niobate

2004 ◽  
Vol 824 ◽  
Author(s):  
Caterina Talerico ◽  
Michael Ochs ◽  
Eric Giffaut
Keyword(s):  
Solid Phase ◽  
Empirical Relation ◽  
Oxide Phase ◽  
X Ray Diffraction ◽  
Ph Values ◽  
Wide Range ◽  
Ph Conditions ◽  
Predicted Values ◽  
Ph Range ◽  
Good Agreement

AbstractThe solubility of niobium was investigated for Ca and pH conditions relevant for cementequilibrated solutions. For the pH range considered (9.5-13.2), the dissolved Nb concentration decreases with increasing pH. Overall, experiments lead to Nb concentrations between 2·10-5 M and 2·10-9 M. For all pH values, the dissolved Nb concentration also decreases systematically with increasing Ca concentration. X-ray diffraction measurements of selected experiments confirmed the presence of a solid Ca-Nb-oxide phase, with CaNb4O11·8H2O (hochelagaite) being the most likely composition. On the basis of these findings an empirical regression model for the prediction of Nb solubility data as a function of pH and Ca concentration was derived. This empirical relation is consistent with the presence of a solubility limiting Ca-Nb solid phase and permits to predict aqueous Nb solubility values in cementitious environments over a relatively wide range of conditions. Predicted values are in good agreement with independent experimental results.

scholarly journals Adsorption of uranyl ion on acid-modified zeolitic mineral clinoptilolite

2009 ◽  
Vol 63 (5) ◽  
pp. 407-414 ◽  
Author(s):  
Srdjan Matijasevic ◽  
Aleksandra Dakovic ◽  
Deana Iles ◽  
Sonja Milicevic
Keyword(s):  
Solid Phase ◽  
Exchange Capacity ◽  
Uranyl Ion ◽  
Ion Adsorption ◽  
Fluorometric Method ◽  
Kinetics Of Adsorption ◽  
Ph Values ◽  
Modified Clinoptilolite ◽  
Kinetics Of

In this paper, the results of adsorption of uranyl ion on acid-modified zeolitic mineral clinoptilolite are presented. Adsorption was investigated at different amounts of solid phase in suspension, as well as at different pH values. The modified clinoptilolite samples were obtained by treatment of clinoptilolite with acids: hydrochloric, oxalyc and citric. Starting and modified clinoptilolites were characterized by chemical analysis, thermal (DT/TG) analysis and by determination of cation exchange capacity, while starting and nonadsorbed amounts of uranyl ion were determined by fluorometric method. Uranyl ion adsorption experiments on natural unmodified zeolitic mineral showed that uranyl ion adsorption was low (29.2%) and that treatment of clinoptilolite with acids significantly increases the adsorption of uranyl ion (>90%). In the case of acid treated clinoptilolites, the highest adsorption of uranyl ion was achieved on clinoptilolite modified with hydrochloric acid. Kinetics of adsorption showed that adsorption of uranyl ion begins very fast and that the most of uranyl ion was adsorbed in first 30 min. Practically, there were no changes in uranyl ion adsorption within next 72 h.

Application of Methyl Silane Coated Iron Oxide Magnetic Nanoparticles for Solid-Phase Extraction and Determination of Fat-Soluble Vitamins by High Performance Liquid Chromatography

2015 ◽  
Vol 98 (2) ◽  
pp. 336-344 ◽  
Author(s):  
Fariborz Momenbeik ◽  
Elham Yazdani
Keyword(s):  
Magnetic Nanoparticles ◽  
High Performance ◽  
Solid Phase ◽  
Pharmaceutical Formulations ◽  
Sample Solution ◽  
Low Concentrations ◽  
Iron Oxide Magnetic Nanoparticles ◽  
Fat Soluble Vitamins ◽  
Good Agreement

Abstract Methyl silane coated Fe3O4 magnetic nanoparticles were used for simultaneous extraction of the fat-soluble vitamins (FSVs). The amounts of extracted vitamins were determined by HPLC. The synthesized Fe3O4 nanoparticles were coated with silica and then modified withtrimethoxymethylsilane (TMMS). The prepared particles were characterized by different methods. The best amounts of silica and TMMS in sorbent synthesis were1.2 and 0.5 mL, respectively. The optimum pH values for the sample solution and washing buffer were 5 and 3, respectively. Application of 100 mg sorbent, 700 μL tetrahydrofuran, 5-fold dilution of the sample solution, and 1 min for sorption and desorption times were among the best conditions. At the optimum conditions, the calibration plots for each vitamin were obtained with good linearity (R2 >0.9992) and suitable linear ranges. This method has a low LOD (<76.1 μg/mL), acceptable repeatability (RSD <5.63%) and reproducibility (RSD<4.71%), and good accuracy (recovery >90.3%). Preconcentration of low concentrations of vitamin D3 was performed, and results showed 3.7 times greater sensitivity after preconcentration. Finally, the amounts of the FSVs in pharmaceutical formulations were determined using the proposed method, and results showed good agreement with those reportedby manufacturers.

scholarly journals Automated Method for Cleanup and Determination of Benomyl and Thiabendazole in Table-Ready Foods

1998 ◽  
Vol 81 (6) ◽  
pp. 1217-1223 ◽  
Author(s):  
Robert A Levine ◽  
Ronald G Luchtefeld ◽  
Marvin L Hopper ◽  
Garrett D Salmon
Keyword(s):  
Methylene Chloride ◽  
Solid Phase ◽  
Strong Cation Exchange ◽  
Automated Method ◽  
On Line ◽  
Diet Study ◽  
Spe Method ◽  
Liquid Chromatographic ◽  
Good Agreement

Abstract An automated solid-phase extraction (SPE) cleanup with on-line liquid chromatographic (LC) analysis was developed to determine residues of benomyl (as carbendazim) and thiabendazole in table- ready food items from the U.S. Food and Drug Administration Total Diet Study (TDS). A strong-cation- exchange cleanup of an acetone extract replaces the methylene chloride solvent partitioning steps in the procedure described in the Pesticide Analytical Manual(PAM). LC analysis is accomplished with a Cs analytical column and tandem fluorescence and UV detection. Recoveries of both analytes from 32 representative TDS foods fortified at 0.05 and 0.5 μg/g were determined. Method precision was evaluated with triplicate recovery assays on 11 foods fortified at both levels. Accuracy was tested further by assaying 47 foods for incurred residues in parallel with the validated PAM procedure for comparison, and good agreement was found. The automated SPE method reduces solvent consumption, analysis time, and labor.

scholarly journals A Rapid HPLC Method for Monitoring Plasma Levels of Caffeine and Theophylline Using Solid Phase Extraction Columns

1986 ◽  
Vol 23 (4) ◽  
pp. 440-446 ◽  
Author(s):  
Clare E Pickard ◽  
A D Stewart ◽  
R Hartley ◽  
M D Lucock
Keyword(s):  
Acetic Acid ◽  
Sample Preparation ◽  
Solid Phase Extraction ◽  
Mobile Phase ◽  
Solid Phase ◽  
Hplc Method ◽  
Phase Extraction ◽  
The Cost ◽  
Good Agreement

A simple HPLC method for the determination of caffeine and theophylline in plasma is described. Separation of theobromine, paraxanthine, theophylline, β-hydroxyethyltheophylline and caffeine is obtained using a mobile phase of 1% acetic acid/methanol (83:17, v/v) and a Waters Associates NOVA-PAK C18 column protected by a Guard-PAK precolumn module containing a Guard-PAK CN cartridge. Rapid sample preparation is achieved by solid-phase extraction columns (Bond-Elut C18, 1 mL capacity) which provide excellent recovery values for both drugs. The cost per sample using this approach can be minimised by column regeneration and re-use. Results obtained for theophylline are in good agreement with values determined by other techniques.

scholarly journals Determination of Antidepressants and Antipsychotics in Dried Blood Spots (DBSs) Collected from Post-Mortem Samples and Evaluation of the Stability over a Three-Month Period

Molecules ◽  
2019 ◽  
Vol 24 (20) ◽  
pp. 3636 ◽  
Author(s):  
Matteo Moretti ◽  
Francesca Freni ◽  
Beatrice Valentini ◽  
Claudia Vignali ◽  
Angelo Groppi ◽  
...  
Keyword(s):  
Room Temperature ◽  
Matrix Effects ◽  
Solid Phase ◽  
Dried Blood Spots ◽  
Post Mortem ◽  
Sample Storage ◽  
Blood Spots ◽  
The Stability ◽  
Good Agreement

An LC-MS/MS method for the identification and quantification of antidepressants and antipsychotics was developed on dried blood spots (DBSs). Moreover, analyte stability on DBSs within a 3-month period was monitored. Aliquots of 85 µL of blood from autopsy cases were pipetted onto DBS cards, which were dried and stored at room temperature. DBSs were analyzed in triplicate immediately, within the following 3 weeks, and after 3 months. For each analysis, a whole blood stain was extracted in phosphate buffer and purified using Solid Phase Extraction (SPE) cartridges in order to avoid matrix effects and injected in the LC-MS/MS system. Thirty-nine molecules were screened. Limits of detection (LODs) ranged between 0.1 and 3.2 ng/mL (g) and 0.1 and 5.2 ng/mL (g) for antidepressants and antipsychotics, respectively. Limits of quantification (LOQs) varied from 5 to 10.0 ng/mL for both. Sixteen cases among the 60 analyzed resulted positive for 17 different analytes; for 14 of these the method was fully validated. A general good agreement between the concentrations on DBSs and those measured in conventional blood samples (collected concurrently and stored at −20 °C) was observed. The degradation/enhancement percentage for most of the substances was lower than 20% within the 3-month period. Our results, obtained from real post-mortem cases, suggest that DBSs can be used for routine sample storage.

The Determination of the Solubility of Amorphous UO2 (Sn and the Mononuclear Hydrolysis Constants of Uranium(IV) at 25° C.

1986 ◽  
Vol 84 ◽  
Author(s):  
Jordi Bruno ◽  
Ignasi Casas ◽  
Bo Lagerman ◽  
Maria Munoz
Keyword(s):  
Stability Constants ◽  
Solubility Data ◽  
Hydrolysis Constants ◽  
Reducing Conditions ◽  
Wide Ph Range ◽  
The Stability ◽  
Ph Range ◽  
Good Agreement

AbstractWe have measured the solubility 8f amorphous UO2in a wide pH range (2 to 10.5), in 0.5 M NaClO, at T=25 C. The species responsible for the solubility are U(OH) + and U'0H)h, with the stability constants lo:1,3=-1.1± 0.1 and log, 4 =- 5.4_.O. 2, respectively. No evidence for U(OH) is f6und up to pH=10.5. The same model explains satisfactorily the solubility data obtained by Parks and Pohl(5) at T=1000 C., in the pH range 1 to 10. The measured solubility of amorphous UO2 (s) in the pH_ýange 6 to 10.5, under reducing conditions, is rather high,. U(IV) =5 10 mols/l. This is in good agreement with previous data of Gayer and Leider(6) and Galkin and Stepanov(9).

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