Determination of the stability constant of Np(V) fluoride complex using a fluoride ion selective electrode

Fluoride complexing of Np(V) has been studied using fluoride ion selective electrode (F-ISE). Free fluoride ion concentrations in the presence of Np(V) were measured at 0.1 and 1.0M ionic strength. The data were used to calculate the stability constant of the fluoride complex of Np(V) and the values obtained are reported here.     

Effect of organic solvents and their dielectric constants on ion selective electrode potential

Summary The effects of mixtures of water with methanol, ethanol, acetone, dimethylsulfoxide (DMSO), andp-dioxane on the lead ion selective electrode potential have been studied. With the exception of DMSO which decreases the potential, other organic solvents stated above show an increased potential effect. Both the lead ion electrode and the silver arsenite electrode show an approximately linear decreasing relationship between the potential and the dielectric constant of organic solvents studied.

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Über die Wirkung organischer Lösungsmittel und ihrer Dielektrizitätskonstante auf das Potential ionenspezifischer Elektroden

Zusammenfassung Die Wirkung von wäßrigem Methanol, Äthanol, Aceton, Dimethylsulfoxid (DMSO) oderp-Dioxane auf das Potential einer bleispezifischen Elektrode wurde untersucht. Mit Ausnahme von DMSO, das dieses Potential vermindert, haben die angeführten organischen Lösungsmittel die entgegengesetzte Wirkung. Die bleispezifische Elektrode und die Silberarsenitelektrode zeigen ein etwa linear abnehmendes Verhältnis zwischen dem Potential und der Dielektrizitätskonstante der angeführten organischen Lösungsmittel.

     

Dimerization of copper(II) decanoate in 1,4-dioxane-water mixed solvents

Complex formation of copper(II) with decanoic acid (HA) has been studied by potentiometric measurement in 1,4-dioxane-water mixtures at a constant ionic concentration of 0.1 mol dm^?3 (Na, H)ClO₄ and at 25°C. The experimental data can be interpreted with the formation of CuA⁺, CuA₂ and Cu₂A₄. The dimerization constant formulated as:

was found to be log K_dim = 3.75, 4.02 and 4.26 for 0.3, 0.4 and 0.5 mole fractions of dioxane, respectively. Absorbances at 373 and 670 nm are interpreted with the aid of the formation constants determined by potentiometry. Solvent effect on the dimerization of the monomeric copper(II) decanoate is discussed on the basis of selective solvation of CuA₂ and Cu₂A₄ with water molecules.     

Thermochemistry of copper(II) ion solvation in aqueous organic solvents

The integral heat effects of CuCl₂ dissolution in aqueous DMSO, aqueous ethanol and aqueous acetone solutions at 298. 15 K in the electrolyte concentration range 0.001–0.01M were measured by means of calorimetry. ΔH _sol ⁰ values were obtained by extrapolation to zero electrolyte concentration. Literature data were used to determine the thermodynamic characteristics of Cu²⁺ transfer from water to aqueous organic solvents.     

Determination of stability constants of cadmium(II) with some amino-acids by use of an ion-selective electrode

Three different methods were used to obtain the stability constants of the complexes of cadmium with several mino-acids. Two made use of an ion-selective electrode; the third was based on pH-measurement only. Values of beta(ml) and beta(ml)(2) obtained in 0.1M KNO(3) at 25 degrees corresponded reasonably for most amino-acids examined and accorded with the values given in the literature, as far as comparison was possible.     

A lead(II) ion selective electrode via a metal complex of poly(hydroxamic acid)

A new lead(II) electrode has been constructed with poly(hydroxamic acid) (PHXA) as the active material and silicone rubber as the supporting material. The electrode gave near Nerstian response over the concentration range 4 × 10⁻⁵−1 × 10⁻²M lead(II). The detection limit of the electrode is approximately 4 × 10⁻⁶M and the electrode works well in the pH range 4.5–6.0. The response time was 50–120 sec over the whole concentration range and the electrode has a working life of at least 4 weeks. Iron(III) severely poisoned the electrode membrane. Nickel(II) and mercury(II) gave very strong interference compared to copper(II), silver(I), cobalt(II), sodium(I), potassium(I), zinc(II) and cadmium(II) which gave some or little interference. Values determined with atomic absorption (AAS) and a commercial lead(II) electrode were in good agreement with those measured with the lead(II) electrode reported here.     

Determination of stability constants of Fe(II), Co(II) and Cu(II)-nitrilotriacetate-penicillamine mixed complexes by electrophoresis

The stability constants of Fe(II), Co(II) and Cu(II)-NTA-penicillamine were determined by paper electrophoresis. The values of these constants were found to be 5.06, 5.16 and 5.28 (log K values), respectively at mu=0.1 and 35 degrees C.     

Highly selective thiocyanate electrode based on bis-bebzoin-semitriethylenetetraamine binuclear copper(II) complex as neutral carrier

A novel selective thiocyanate PVC membrane electrode based on bis-bebzoin-semitriethylenetetraamine binuclear copper(II) [Cu(II)₂–BBSTA] as neutral carrier is reported, which displays an anti-Hofmeister selectivity sequence in following order: SCN⁻ > ClO₄⁻ > I⁻ >Sal⁻ >SO₃²⁻ >NO₃⁻ > H₂PO₄⁻ > Cl⁻ >NO₂⁻ > SO₄²⁻. The electrode exhibits Nernstian potential linear range to thiocyanate from 1.0 × 10⁻¹ to 9.0 × 10⁻⁷ mol/l with a detection limit 7.0 × 10⁻⁷ mol/l and a slope of −57.0 mV/decade in pH 5.0 of phosphorate buffer solution at 25 °C. The response mechanism is discussed in view of the AC impedance technique and the UV spectroscopy technique. From comparison of potentiometric response characteristics between the binuclear metallic complex copper(II) [Cu(II)₂–BBSTA] and mononuclear copper(II) metallic complex [Cu(II)–BBSDA], an enhanced response towards thiocyanate from the electrode based on binuclear metallic complex copper (II) [Cu(II)₂–BBSTA] was observed. The electrode based on binuclear copper(II) compound was used to determine the thiocyanate content in waste water with satisfactory results.     

Kinetic-potentiometric assay of formaldehyde in pharmaceutical and industrial samples, monitored by copper solid ion selective electrode, after its reaction with the copper(II)-bis-(ethylenediamine) complex

A kinetic-potentiometric method is described for the quantitative assay of formaldehyde (HCHO) in pharmaceutical and industrial preparations. It is based on the reaction of HCHO with (ethylenediamine)-Cu(II)-sulfate [Cu(CH₂NH₂)₂(H₂O)₂] · SO₄. The changes in potential, resulting from the release of the Cu(II) cations, are monitored with a Cu(II)-ion selective electrode. The calibration curve for the HCHO is linear in the concentration range 50–250 mg L⁻¹, with a limit of detection of 8.5 mg L⁻¹. The method shows very good reproducibility with an RSD of 2.6% for successive injections (n = 5) of 150 mg L⁻¹ HCHO primary solution, while it is interference free. The method was successfully tested in various industrial and pharmaceutical preparations.     

Thiocyanate-selective electrode based on N-salicylidene-benzylamineato copper(II) complex

Highly selective poly(vinyl chloride) (PVC) membrane electrode based on N-salicylidene-benzylamineato copper(II) complexes [Cu(SBA)₂] as new carriers towards thiocyanate-selective electrode was reported. The influence of membrane composition, pH and possible interfering anions were investigated on the response properties of the electrode. The resulting electrode exhibits anti-Hofmeister selectivity sequence: SCN⁻ > ClO₄⁻ > Sal⁻ > I⁻ > Br⁻ > NO₃⁻ > NO₂⁻ > SO₃²⁻ > H₂PO₄⁻ > Cl⁻ > SO₄²⁻, and a near-Nernstian potential linear range for thiocyanate from 1.0 × 10⁻¹ to 9.0 × 10⁻⁷ M with a detection limit of 7.0 10⁻⁷ M and a slope of , over a wide pH range of 3.0–9.0 in phosphate buffer solution at 20°C. The proposed electrode has a fast response time of about 5–10 s and can be used for at least 3 months without any considerable divergence in potential. The electrode was successfully applied to the determination of thiocyanate in waste water and human urine and saliva samples. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 3, pp. 293–299. The text was submitted by the authors in English.     

Determination of stability constant of copper(II) with thiosemicarbazide by use of a cupric ion-selective electrode

The stability constant of copper(II)—thiosemicarbazide complex has been determined potentiometrically by means of a cupric ion-selective electrode. Value of logK_CuL2 obtained in 0. 1 M KNO₃ at 25 °C corresponded well with the values given in the literature measured spectrophotometrically.     

Determination of stability constants for alkaline-earth and alkali metal ion complexes of glycine by spectrophotometry

The complex equilibria between alkaline-earth and alkali metal ions with glycine were studied by a spectrophotometric method. The following stability constant (concentration) values valid at 25 degrees and ionic strength 1.0M were found: K(HL) = 10(9.57), K(LiL) = 10(-1.2), K(BaL) = 10(-0.40), K(SrL) = 10(0.14), K(CaL) = 10(0.55), K(MgL) = 10(1.17).     

A liquid-state copper(II) ion-selective electrode containing a complex of Cu(II) with salicylaniline

A new liquid-state ion-selective electrode based on a complex of Cu(II) with salicylaniline is described. The electrode shows linear dependence of potential on the activity of Cu(2+) in the range from 5 x 10(-6) to 0.1M, with a slope of 28.3 mV/pCu at 18 degrees . The electrode shows a better selectivity relative to Ag(I) and Hg(II) than other copper(II) ion-selective electrodes. The possibilities for using the electrode for determination of copper in the presence of interfering cations are described.     

Determination of copper(II) in wastewater by electroplating samples using a PVC-membrane copper(II)-selective electrode

A PVC membrane containing 4-amino-6-methyl-1,2,4-triazin-3,5-dithione (AMTD) as a suitable ionophore, exhibits a Nernstian response for Cu²⁺ ions over a wide concentration range up to 1 × 10⁻¹ and 1 × 10⁻⁶ M, with a detection limit of 7.5 × 10⁻⁷ M in the pH range 3.0–7.5. It has a fast response time (<15 s) and can be used for at least 12 weeks without any major deviation in the potential. The electrode revealed a very good selectivity with respect to all common alkali, alkaline-earth, transition, and heavy-metal ions. It was successfully applied to the recovery of copper ions from wastewater. The electrode was also used as an indicator electrode in the potentiometric titration of Cu(II) ions with EDTA. The text was submitted by the authors in English.     

Estimation of stability constants of copper(II) and nickel(II) chelates with dipeptides by using topological indices

The estimation of the overall stability constants β₁ of copper(II) and nickel(II) chelates with dipeptides was performed by using the model with the valence connectivity index of the 3rd order (³χ^v). It was done by dividing β₁ to its constituting constants K₁ and K_a, and subsequently by dividing the basic set into subsets or treating the chelate rings as separate units. Altogether 15 copper(II) and eight nickel(II) chelates with dipeptides were investigated. Six models for the estimation of log K₁ and pK_a were checked, most of them by usage of indicator variables (for differentiation of copper(II) and nickel(II) complexes or subclasses of ligands). Estimates of log β₁ gave the range of rms values from 0.19 to 0.27. For the best model, errors of estimates were less than 0.34.     

A highly selective turn-on fluorescent chemosensor for copper(II) ion

A new pyrene derivative (1) containing a diaminomaleonitrile moiety exhibits high selectivity for Cu²⁺ detection. Significant fluorescence enhancement was observed with chemosensor 1 in the presence of Cu²⁺. However, the metal ions Ag⁺, Ca²⁺, Cd²⁺, Co²⁺, Fe²⁺, Fe³⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ produced only minor changes in fluorescence values for the system. The apparent association constant (K_a) of Cu²⁺ binding in chemosensor 1 was found to be 5.55×10³ M⁻¹. The maximum fluorescence enhancement caused by Cu²⁺ binding in chemosensor 1 was observed over the pH range 5-7.5.     

离子选择性电极法测定聚合硫酸铁絮凝剂中的铅

无机高分子絮凝剂聚合硫酸铁(PFS)是我国最有前景的水处理剂之一,其应用领域广泛,除工业废水处理、市政污水处理外还应用于自来水净化处理。目前,制备聚合硫酸铁多采用工业废料,不可避免地含有不同量的铅。国家标准GB14591-1993规定,作为饮用水水处理剂PFS中的铅质量分数不得超过0.0010%。目前用于工业废水中铅量的测定方法有丁基罗丹明B光度法[1]、结晶紫光度法[2]等。光度法测定中必须进行萃取、离子交换、共沉淀等分离富集操作,这就大大增加了分析步骤和操作难度,使铅的吸光光度测定的应用受到一定的限制。最近罗平、郑怀礼等[3,…     

Amperometric determination of sulfide ion by glassy carbon electrode modified with multiwall carbon nanotubes and copper (II) phenanthroline complex

Electrocatalytic oxidation of sulfide ion on a glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNTs) and a copper (II) complex was investigated. The Cu(II) complex was used due to the reversibility of the Cu(II)/Cu(III) redox couple. The MWCNTs are evaluated as a transducer, stabilizer and immobilization matrix for the construction of amperometric sensor based on Cu(II) complex adsorbed on MWCNTs immobilized on the surface of GCE. The modified GCE was applied to the selective amperometric detection of sulfide at a potential of 0.47 V (vs. Ag/AgCl) at pH 8.0. The calibration graph was linear in the concentration range of 5 µM–400 µM; while the limit of detection was 1.2 µM, the sensitivity was 34 nA µM^?1. The interference effects of SO₃ ^2?, SO₄ ^2?, S₂O₃ ^2?, S₄O₆ ^2?, Cysteine, and Cystein were negligible at the concentration ratios more than 40 times. The modified electrode is more stable with time and more easily restorable than unmodified electrode surface. Also, modified electrode permits detection of sulfide ion by its oxidation at lower anodic potentials.      

A new nano-composite electrode as a copper (II) selective potentiometric sensor

A macrocyclic ligand “7,10,13-triaza-1-thia-4,16-dioxa-20,24-dimethyl-2,3;17,18-dibenzo-cyclooctadecane-6,14-dione” as an efficient ionophore was used into a new Cu²⁺ nano-composite potentiometric carbon paste sensor containing multi-walled carbon nanotubes (MWCNTs), nanosilica particles, and room temperature ionic liquid (1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMP]Tf₂N). This potentiometric sensor responds to copper ions in a wide linear dynamic range of 4.50 × 10^?8 to 1.00 × 10^?2 mol L^?1 with Nernstian slope of 29.64 ± 0.10 mV per decade. The detection limit of 2.34 × 10^?8 mol L^?1 was obtained at the pH range 3.5–6.0. It has a fast response with response time of about 10 s, and can be used for at least 16 weeks without any considerable divergence in the potentials. The suggested sensor thus allows sensitive, selective, simple, low cost, and stable electrochemical sensing of Cu²⁺ ions in the presence of a large number of alkali, alkaline earth, transition and heavy metal ions. This sensor was successfully applied in the determination of copper ions in water and waste water samples.     

Potentiometric determination of stability constants of inorganic cyclophosphate complexes with copper(II), cadmium(II) and lead(II) ions

The stability constants of the complexes of cyclophosphate anions and copper(II), cadmium(II) and lead(II) ions were determined by potentiometry with the use of ion-selective electrodes. For each metal ion, the stability constant of the 1:1 complex increases linearly with the charge on the phosphate ion. For the same cyclophosphate ion, the stability constants also increase with increase in the crystal radii of the cation, i.e. in the order: Cu²⁺ < Cd²⁺ < Pb²⁺. These results suggest that the complex formed is a typical outer-sphere type based on electrostatic forces.