单柱离子色谱法测定硒酸根和亚硒酸根的研究

本实验采用单柱离子色谱系统,在SeO_4~(2-)、SeO_3~(2-)与F~-、Cl~-、NO_3~-、SO_4~(2-)离子共存时,以1.0mmol/L邻苯二甲酸氢钾为淋洗液测定了SeO_4~(2-),以1.0mmol/LKNO_3为淋洗液测定了SeO_3~(2-)。SeO_4~(1-)和SeO_3~(2-)的最低检出浓度分别为0.3μg/mL和0.7μg/mL,线性范围分别为0.8～80μg/mL和1.4～150μg/mL,相对标准偏差分别为2.01%和1.85%。并应用本方法测定了加SeO_4~(2-)和SeO_3~(2-)的自来水样,SeO_4~(2-)和SeO_3~(2-)的回收率分别为96%和98%。     

A Spectrophotometric Study on Uranyl Nitrate Complexation to 150 °C

The formation constant of the mononitratouranyl complex was studied spectrophotometrically at temperatures of 25, 40, 55, 70, 100 and 150 °C (298, 313, 328, 343, 373 and 423 K). The uranyl ion concentration was fixed at approximately 0.008 mol⋅kg⁻¹ and the ligand concentration was varied from 0.05 to 3.14 mol⋅kg⁻¹. The uranyl nitrate complex, UO₂NO₃⁺, is weak at 298 K but its equilibrium constant (at zero ionic strength) increases with temperature from log ₁₀ β ₁=−0.19±0.02 (298 K) to 0.78±0.04 (423 K).     

Thermodynamics of substituted rhodanine II: Binary complexes of Th(IV), UO2(II), Ce(III), and La(III) with 3-benzamidorhodanine and its derivatives

Summary Th(IV), UO₂(II), Ce(III) and La(III) chelates with 3-benzamidorhodanine and its derivatives have been investigated potentiometrically in 0.1M KCl and 20% (v/v) ethanol-water medium. The stability of the formed complexes increases in the order Th(IV)>UO₂(II)>Ce(III)>La(III). For the same metal ion, the stability of the chelates is found to increase with decreasing temperature, ionic strength, dielectric constant of the medium and by increasing the electron repelling property of the substituent. The thermodynamic parameters (G, H and S) for complexation are evaluated and discussed. The formation of the complexes has been found to be spontaneous, exothermic and entropically favourable.

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Thermodynamik von substituiertem Rhodanin II: Binäre Komplexe von Th(IV), UO₂(II), Ce(III) und La(III) mit 3-Benzamidorhodanin und seinen Derivaten

Zusammenfassung Th(IV)-, UO₂(II)-, Ce(III)- und La(III)-Chelate mit 3-Benzamidorhodanin und seinen Derivaten wurden in 0.1M KCl und 20% (/) Ethanol-Wasser potentiometrisch untersucht. Die Stabilität der gebildeten Komplexe steigt in der Reihenfolge Th(IV)>UO₂(II)>Ce(III)>La(III). Für ein- und dasselbe Metallion steigt die Stabilität der Chelate mit sinkender Temperatur, Ionenstärke und Dielektrizitätskonstante des Mediums und mit steigender Elektronenabstoßungsfähigkeit des Substituenten. Die thermodynamischen Parameter (G, H und S) für die Komplexbildungsreaktion werden bestimmt und diskutiert. Die Bildung der Komplexe erweist sich als spontan, exotherm und entropisch begünstigt.

     

Experimental evidences for some unusual divalent cation complexes of valinomycin

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M ²⁺ (aq) + 1 · Sr²⁺ (nb) ⇄ 1 · M ²⁺ (nb) + Sr²⁺ (aq) taking place in the two-phase water-nitrobenzene system (M ²⁺ = Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, UO₂ ²⁺, Fe²⁺, Co²⁺, and Ni²⁺; 1 = valinomycin; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the 1 · M ²⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the order Fe²⁺ < Cd²⁺, Co²⁺ < Ni²⁺ < UO₂ ²⁺, Zn²⁺ < Cu²⁺ < Pb²⁺. Correspondence: Emanuel Makrlík, Faculty of Applied Sciences, University of West Bohemia, Pilsen, Czech Republic.     

Stability constants of some metal cation complexes of tetraphenyl <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylcalix[4]arene tetraketone in nitrobenzene saturated with water

Abstract  From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium taking place in the two-phase water–nitrobenzene system (M²⁺ = Ca²⁺, Ba²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, UO₂ ²⁺, Mn²⁺, Co²⁺, Ni²⁺; 1 = tetraphenyl p-tert-butylcalix[4]arene tetraketone; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the 1 · M²⁺ complexes in water-saturated nitrobenzene were calculated; they were found to increase in the cation order Ba²⁺, Mn²⁺ < Co²⁺ < Cu²⁺, Ni²⁺ < Zn²⁺, Cd²⁺, UO₂ ²⁺ < Ca²⁺ < Pb²⁺. Graphical abstract        

Metal complexes stability constant determination by hyphenation of capillary electrophoresis with inductively coupled plasma mass spectrometry: The case of 1:1 metal-to-ligand stoichiometry

Nuclear energy development has raised new issues like radionuclides biogeochemistry. The modelling of their biochemical properties involves the accurate determination of thermodynamical data, like stability constants. This can be achieved by using hyphenated capillary electrophoresis (CE)–ICPMS and the method was applied successfully on 1:1 lanthanum–oxalate and uranyl–oxalate complexes. Several significant steps are discussed: choice of analytical conditions, electrophoretic mobility calculation, mathematical treatment of experimental data by using linear regressions, ligand concentration and ionic strength corrections. The following values were obtained with a good precision for lanthanum–oxalate and uranyl–oxalate complexes: log(K°(LaOxa⁺)) = 6.10 ± 0.10 and log(K°(UO₂Oxa)) = 6.40 ± 0.30, respectively, at infinite dilution. These values are consistent with the literature data, showing CE–ICPMS potential for metal complexes stability constants determination.     

Solvent extraction of univalent cations into nitrobenzene using sodium dicarbollylcobaltate and tetraphenyl p-tert-butylcalix[4]arene tetraketone

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the equilibrium M ⁺(aq) + 1 · Na⁺ (nb) ⇄ 1 · M ⁺ (nb) + Na⁺ (aq) taking place in the two-phase water-nitrobenzene system (M ⁺ = Li⁺, H₃O⁺, NH₄ ⁺, Ag⁺, K⁺, Rb⁺, Tl⁺, Cs⁺; 1 = tetraphenyl p-tert-butylcalix[4]arene tetraketone; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the 1 · M ⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the order Cs⁺ < Rb⁺ < Tl⁺ < K⁺ < NH₄ ⁺ < Ag⁺ < H₃O⁺ < Li⁺. Correspondence: Emanuel Makrlík, Faculty of Applied Sciences, University of West Bohemia, Pilsen, Czech Republic.     

Synthesis,complex formation kinetics and thermodynamic study of some acyclic polyamine and N2O2 ligands with copper(II)

The polydentate ligands, 3-(2-aminocyclohexylamino)-2-(2-aminocyclohexyl aminomethyl) propionic acid (L¹ ), 4,7,10-triazatridecanedinitrile trihydrochloride (L² ), and 2,2′-(ethane-1,2-diyl) bis(methylazanediyl) diethanol (L³ ) were prepared and their structures investigated by FT-IR, NMR, and MS. The kinetics of complex formation between Cu(II) and L¹, L², and L³ were investigated in acidic aqueous solutions using the stopped-flow method. The stability constants of the complexes were determined by spectrophotometric titration (T?=?293?K, μ?=?0.1?mol?L^?1 NaClO₄), using a diode array UV-Vis spectrophotometer equipped with peristaltic pump and pH meter. The stability constants for the complexes were CuL^1?>?CuL^2?>?CuL³. Activation enthalpies (ΔH#) of these complexes were 55?kJ?mol^?1 for CuL¹, 61?kJ?mol^?1 for CuL², and 36?kJ?mol^?1 for CuL³, respectively.     

Thermodynamic Model for the Solubility of TcO2⋅xH2O in Aqueous Oxalate Systems

The room temperature solubility of amorphous, hydrous technetium(IV) oxide (TcO₂⋅xH₂O) was studied across a broad range of pH values extending from 1.5 to 12 and in oxalate concentrations from dilute (10⁻⁶ mol⋅kg⁻¹) to complete saturation with respect to sodium bioxalate at lower pH values, and to saturation with respect to sodium oxalate at higher pH values. The solubility was measured to very long equilibration times (i.e., as long a 1000 days or longer). The thermodynamic modeling results show that the dominant species in solution must have at least one more hydroxyl moiety present in the complex than proposed by previous investigators (e.g., TcO(OH)Ox⁻ rather than TcO(Ox)(aq)). Inclusion of the single previously unidentified species TcO(OH)Ox⁻ in our aqueous thermodynamic model explains a wider range of observed solubility data for TcO₂⋅xH₂O(am) in the presence of oxalate and over a broad range of pH values. Inclusion of this species is also supported by the recently proposed thermodynamic data for the TcO(OH)⁺ hydrolysis species that indicates that this species is stable at pH values as low as one.     

Optimization of the determination of inorganic and organic selenium species using high-performance liquid chromatography-electrothermal atomic absorption spectrometry

The liquid chromatographic simultaneous separation of selenite, selenate, selenocystine and selenomethionine was studied with a selenium-specific detector; electrothermal atomic absorption spectrometry. Three chromatographic modes were compared; two ion-pairing ones using either a cationic or an anionic reagent and ion-exchange. Separation parameters such as composition, pH and concentration of the mobile phase were investigated. The influence of chromatographic conditions on the sensitivity of the detector is studied. The ion-exchange method was determined to give the best results, with detection limits ranging from 8 to 17 μg l⁻¹ within a 30 min separation time. An application of this method to the analysis of seleno compounds present in a selenium-rich yeast after enzymic hydrolysis extraction is presented.     

Lanthanide complexation with CMPO and CMPO-calix[4]arenes in solution: spectrophotometric and electrospray mass spectrometric approaches

The binding of lanthanide(III) cations with organophosphorous ligands like CMPO and related calix[4]arene-based derivatives have been investigated using two experimental methods. The stability constants of the lanthanum, europium and ytterbium complexes were first determined in methanol by UV absorption spectrophotometry in the presence of nitrate or chloride anions. The results showed that the stoichiometry and the stability of the complexes formed depend on the position of the CMPO moieties either on the wide or the narrow rim of the calixarene scaffold, the nature of the medium, the conformational mobility of the ligands. Complexation of lanthanum was also followed by ESI-mass spectrometry in the same solvent. This method confirmed the stoichiometry of the complexes, giving also structural information, like coordination of anion or solvent molecules to the complexes, and allowed the calculation of distribution curves in good agreement with those derived from the spectrophotometric results. This is an important result showing that ESI-MS can be used to provide with quantitative information when absorption spectrophotometry is not applicable, i.e. for systems where complexation leads to weak spectral changes.     

Potentiometric studies on the complexes of some trivalent rare earths with 5-chloropyridine-2,3-diol

The complexes of some rare earths [Ce(III), Pr(III), Nd(III), Sm(III), Tb(III), Dy(III), and Ho(III)] with 5-chloropyridine-2,3-diol (CPD) were studied potentiometrically in 50% dioxane-water at a ionic strength of 0.1M (NaClO₄) at 35±0.1 °C. The proton-ligand stability constant ofCPD and the stability constants of its complexes with the metals have been determined using theCalvin-Bjerrum technique as modified byIrving andRossotti. The order of the stability constants is found to be Ce < Pr < Nd < Sm < Tb < Dy < Ho.

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Potentiometrische Untersuchungen der Komplexe einiger trivalenter Seltenerdmetalle mit 5-Chlorpyridin-2,3-diol

Zusammenfassung Es wurden die Komplexe von Ce(III), Pr(III), Nd(III), Sm(III), Tb(III), Dy(III) und Ho(III) mit 5-Chlorpyridin-2,3-diol (CPD) in 50% Dioxan-Wasser bei einer Ionenstärke von 0,1M (NaClO₄) und einer Temperatur von 35±0,1 °C potentiometrisch untersucht. Die Proton-Ligand-Stabilitätskonstante vonCPD und die Stabilitätskonstanten der Metallkomplexe wurden nach der Methode vonCalvin-Bjerrum mit derIrving-Rossotti-Modifikation bestimmt. Die Reihenfolge der Stabilitätskonstanten ergab sich folgendermaßen: Ce < Pr < Nd < Sm < Tb < Dy < Ho.

     

Influence of metal loading and humic acid functional groups on the complexation behavior of trivalent lanthanides analyzed by CE-ICP-MS

The complexation behavior of Aldrich humic acid (AHA) and a modified humic acid (AHA-PB) with blocked phenolic hydroxyl groups for trivalent lanthanides (Ln) is compared, and their influence on the mobility of Ln(III) in an aquifer is analyzed. As speciation technique, capillary electrophoresis (CE) was hyphenated with inductively coupled plasma mass spectrometry (ICP-MS). For metal loading experiments 25 mg L⁻¹ of AHA and different concentrations (c_Ln(Eu+Gd) = 100–6000 μg L⁻¹) of Eu(III) and Gd(III) in 10 mM NaClO₄ at pH 5 were applied. By CE-ICP-MS, three Ln-fractions, assumed to be uncomplexed, weakly and strongly AHA-complexed metal can be detected. For the used Ln/AHA-ratios conservative complex stability constants log β_LnAHA decrease from 6.33 (100 μg L⁻¹ Ln³⁺) to 4.31 (6000 μg L⁻¹ Ln³⁺) with growing Ln-content. In order to verify the postulated weaker and stronger humic acid binding sites for trivalent Eu and Gd, a modified AHA with blocked functional groups was used. For these experiments 500 μg L⁻¹ Eu and 25 mg L⁻¹ AHA and AHA-PB in 10 mM NaClO₄ at pH-values ranging from 3 to 10 have been applied. With AHA-PB, where 84% of the phenolic OH-groups and 40% of the COOH-groups were blocked, Eu complexation was significantly lower, especially at the strong binding sites. The log β-values decrease from 6.11 (pH 10) to 5.61 at pH 3 (AHA) and for AHA-PB from 6.01 (pH 7) to 3.94 at pH 3. As a potential consequence, particularly humic acids with a high amount of strong binding sites (e.g. phenolic OH- and COOH-groups) can be responsible for a higher metal mobility in the aquifer due to the formation of dissolved negatively charged metal-humate species.