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Ion specific effects are ubiquitous in solutions and govern a large number of colloidal phenomena. To date, a substantial and sustained effort has been directed at understanding the underlying molecular interactions. As a new approach, we address this issue by sensitive 1H NMR methods that measure the electrophoretic mobility and the self-diffusion coefficient of poly(N-isopropylacrylamide) (PNIPAM) chains in bulk aqueous solution in the presence of salts with the anion component varied from kosmotropes to chaotropes along the Hofmeister series. The accuracy of the applied electrophoretic NMR experiments is exceptionally high, on the order of 10–10 m2/(V s), corresponding to roughly 10–4 elementary charges per monomer effectively associated with the neutral polymer. We find that chaotropic anions associate to PNIPAM with an apparent Langmuir-type saturation behavior. The polymer chains remain extended upon ion association, and momentum transfer from anion to polymer is only partial which indicates weak attractive short-range forces between anion and polymer and, thereby and in contrast to some other ion–polymer systems, the lack of well-defined binding sites. QC 20210607

Tritopic ion‐pair receptors can bind bivalent salts in solution; yet, these salts have a tendency to form ion‐pairs even in the absence of receptors. The extent to which such receptors can enhance ion pairing has however remained elusive. Here, we study ion pairing of M2+ (Ba2+, Sr2+) and X− (I−, ClO4 −) in acetonitrile with and without a dichlorooxacalix[2]arene[2]triazine‐related receptor containing a pentaethylene‐glycol moiety. We find marked ion association already in receptor‐free solutions. When present, most of the MX+ ion‐pairs are bound to the receptor and the overall degree of ion association is enhanced due to coordinative, hydrogen‐bonding, and anion‐π interactions. The receptor shows higher selectivity for iodides but also stabilizes perchlorates, despite the latter are often considered as weakly coordinating anions. Our results show that ion‐pair binding is strongly correlated to ion pairing in these solutions, thereby highlighting the importance of taking ion association in organic solvents into account., Pairing in the spotlight: Sr2+ and Ba2+ salts form ion pairs with iodide and perchlorate anions in acetonitrile. Adding a dichlorooxacalix[2]arene[2]triazine‐related ion‐pair receptor stabilizes these ion pairs and enhances the overall degree of ion pairing, as evidenced from their contribution to the dielectric loss spectra.

A simple and efficient cloud point spectrophotometric method has been used for the determination of salbutamol sulphate and methyldopa both in pure and pharmaceutical preparations. The procedure was based on the ion association formation with eosin Y. The extraction of ion association, drown to Triton X-114 micelles, was measured spectrophotometrically. The phase separation was studied and optimized. Beer's law was rectilinear over the concentration ranges of 0.1-20 and 0.3-10 µg/mL with molar absorptivity 4x104 and 5.7x104 L.mol-1 cm-1 and average recovery 98.21% and 101.27% for the above drugs, respectively. The method was applied successfully for the determination of salbutamol sulphate and methyldopa in pharmaceuticals.

The complex formation between the anionic chelate of molybdenum(VI) with the bidentate ligand of 3,5-dinitrocatechol (3,5-DNC) and its ion-association with the cation of 2,3,5-triphenyl-2 Н -tetrazolium chloride (TTC) in the liquid-liquid extraction system Mo(VI)‒3,5-DNC‒TTC‒H 2 O‒CHCl 3 were studied by spectrophotometry. The validity of Beer’s law was checked and some analytical characteristics of the system were calculated under the optimum conditions for the chelate formation and extraction. The effect of various co-existing ions and reagents on the process of chelate formation and ion-association was investigated. The molar ratio of the components in the ion-associated complex Mo(VI)–3,5-DNC–TTC was determined by independent methods. The association process in aqueous phase and the extraction equilibria were investigated and quantitatively characterized by the following equilibrium constants: association constant, distribution constant, extraction constant and recovery factor. Based on this, a reaction scheme, a general formula and a structural formula of the complex were suggested.

This work presents a successfulness of the methodology of solution cast technique for fabrication of polymer blend electrolytes based on chitosan (CS): potato starch (PS) doped with various amounts of ammonium tetrafluoroborate (NH4BF4). In this work we demonstrated that association of ions is the main drawback for the NH4BF4 salt. Low DC conductivity of the films displays the non availability of the present system for applications. To look at the electrical properties, structural, and morphological properties, electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD), and Field emission scanning electron microscopy (FESEM), respectively were used. From the EIS measurement the highest conductivity of the system was found to be 3.07 × 10−8 S/cm which is too low for device applications including batteries and supercapacitors. The increase of bulk resistance is an indication for the recombination of cation and anion of the salt at high concentration. Sharp peaks were observed in the XRD spectra at high salt concentration. The morphological outcomes display protruded salts with large size at high salt concentration. The large value of dielectric constant at low frequency region is associated to electrode polarization (EP) while their decline with increasing frequency is ascribed to the lag of polarization of ion with respect to the quick orientation of dipole species because of the applied AC field. The M″ peak asymmetry displays the distribution of relaxation time.

Liquid-liquid extraction-chromogenic systems for vanadium(V) based on xylometazoline hydrochloride (XMZ) and azo derivatives of resorcinol (ADRs) were studied. The following ADRs were used: 4-(2-thiazolylazo)resorcinol (TAR), 5-methyl-4-(2-thiazolylazo)resorcinol (MTAR), and 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR). Concentration of the reagents, pH of the aqueous medium and shaking time were subjects of optimization experiments. The chloroform-extracted ternary complexes were of composition 1:1:1. The molar absorptivity coefficients ( e l ), absorption maxima ( l ), constants of extraction (Log K ), and fractions extracted ( E %) were found to be e 553 = 2.50 ´ 10 4 dm 3 mol –1 cm –1 , Log K = 3.5, and E = 96% (ADR = TAR); e 550 = 1.88 ´ 10 4 dm 3 mol –1 cm –1 , Log K = 3.4, and E = 98% (ADR = MTAR); and e 554 = 2.62 ´ 10 4 dm 3 mol –1 cm –1 , Log K = 5.0, and E = 99.5% (ADR = HTAR). The Sandell’s sensitivities and Beer’s law limits were determined as well.

Conductivity plays vital role in drug diffusion. Thermodynamic parameters affected by substituents of drug. Thermodynamic parameters of 1, 3, 5 –triazinothiocarbamide (1a) have been investigated by using conductometrically carried out at different molar concentrations. This work highlights investigation of G, K and µ values. The thermodynamic parameters viz. ΔH, ΔS and ∆G for ion pair formation determine from the value of ion association constant. This technique is suitable and accurate to study of pharmokinetics and pharmodynamics parameters.

Background: The thermophysical properties of 1-octyl-3-methylimidazolium salicylate as an active pharmaceutical ingredient based on ionic liquid have been investigated in the presence of aqueous solutions of glycine. Therefore, the scope of this article was to determine these properties by measuring the densities, speeds of sound, viscosities, electrical conductances and refractive indices for ternary (glycine + 1-octyl-3-methylimidazolium salicylate + water) soloutions at T = 298.15 K. Methods: A commercial density and speed of sound measurement apparatus was used to measure the density and speed of sound data. Viscosities, electrical conductivities and refractive indices of the studied solutions were measured using digital viscometer, conductivity meter and refractometer, respectively. Results: Variety of properties such as partial molar volume of transfer ∆traV0ϕ, partial molar isentropic compressibility of transfer ∆traK0ϕ, viscosity B-coefficients of transfer ∆traB, ion association constants (KA) and molar refraction RD were determined to investigate the solute-solute and solute-solvent interactions in these systems. Conclusion: The positive values of transfer properties including partial molar volume of transfer (∆traV0ϕ), partial molar isentropic compressibility of transfer (∆traK0ϕ), and viscosity B-coefficients of transfer (∆traB) indicated that in these systems, the ion-polar and polar-polar interactions are dominant. The calculated hydration number showed that dehydration of glycine occurs in presence of this ionic liquid.

A better understanding of the solution chemistry of the lanthanide (Ln) salts in water would have wide ranging implications in materials processing, waste management, element tracing, medicine and many more fields. This is particularly true for minerals processing, given governmental concerns about lanthanide security of supply and the drive to identify environmentally sustainable processing routes. Despite much effort, even in simple systems, the mechanisms and thermodynamics of LnIII association with small anions remain unclear. In the present study, molecular dynamics (MD), using a newly developed force field, provide new insights into LnCl3(aq) solutions. The force field accurately reproduces the structure and dynamics of Nd3+, Gd3+ and Er3+ in water when compared to calculations using density functional theory (DFT). Adaptive‐bias MD simulations show that the mechanisms for ion pairing change from dissociative to associative exchange depending upon cation size. Thermodynamics of association reveal that whereas ion pairing is favourable, the equilibrium distribution of species at low concentration is dominated by weakly bound solvent‐shared and solvent‐separated ion pairs, rather than contact ion pairs, reconciling a number of contrasting observations of LnIII–Cl association in the literature. In addition, we show that the thermodynamic stabilities of a range of inner sphere and outer sphere LnClx(3-x)+ coordination complexes are comparable and that the kinetics of anion binding to cations may control solution speciation distributions beyond ion pairs. The techniques adopted in this work provide a framework with which to investigate more complex solution chemistries of cations in water.

Mechanistic pathways relevant to mineralization are not well‐understood fundamentally, let alone in the context of their biological and geological environments. Through quantitative analysis of ion association at near‐neutral pH, we identify the involvement of HCO3 − ions in CaCO3 nucleation. Incorporation of HCO3 − ions into the structure of amorphous intermediates is corroborated by solid‐state nuclear magnetic resonance spectroscopy, complemented by quantum mechanical calculations and molecular dynamics simulations. We identify the roles of HCO3 − ions as being through (i) competition for ion association during the formation of ion pairs and ion clusters prior to nucleation and (ii) incorporation as a significant structural component of amorphous mineral particles. The roles of HCO3 − ions as active soluble species and structural constituents in CaCO3 formation are of fundamental importance and provide a basis for a better understanding of physiological and geological mineralization., An important role of bicarbonate at near‐neutral pH during CaCO3 formation was found. Its structural incorporation in amorphous intermediates, revealed by a combination of potentiometric titrations, NMR, computer simulations, and other techniques, can be quantitatively explained by a model based on the binding of bicarbonate ions to pre‐nucleation clusters. The findings seem to be crucial for a better understanding of, e.g., CaCO3 biomineralization.

We present a novel ‘shifting-reference concentration-cell’ method, altering the traditional protocol for measuring liquid-junction potentials by using a sequence of reference concentrations in regularly spaced intervals, rather than a fixed reference. The method, applied to solutions of lithium hexafluorophosphate (LiPF6) in propylene carbonate (PC) and ethyl methyl carbonate (EMC) at 25 °C, helps to determine thermodynamic factors more accurately, and is useful across a wider concentration range. For LiPF6:PC, good agreement with prior fixed-reference measurements is shown, and new data at low concentrations is consistent with Debye–Huckel theory. Original composition-dependent property correlations are produced for LiPF6:EMC up to 2 M, including the density and thermodynamic factor, as well as isothermal-transport properties such as transference number, conductivity, diffusivity, and viscosity. Polarization-relaxation simulations validate these correlations. For LiPF6:EMC, the low thermodynamic factor and cation/anion Stefan–Maxwell diffusivity, as well as Walden analysis, suggest that ion association dominates, even at high dilution.

In concentrated electrolytes with asymmetric or irregular ions, such as ionic liquids and solvent-in-salt electrolytes, ion association is more complicated than simple ion-pairing. Large branched aggregates can form at significant concentrations at even moderate salt concentrations. When the extent of ion association reaches a certain threshold, a percolating ionic gel network can form spontaneously. Gelation is a phenomenon that is well known in polymer physics, but it is practically unstudied in concentrated electrolytes. However, despite this fact, the ion-pairing description is often applied to these systems for the sake of simplicity. In this work, drawing strongly from established theories in polymer physics, we develop a simple thermodynamic model of reversible ionic aggregation and gelation in concentrated electrolytes accounting for the competition between ion solvation and ion association. Our model describes, with the use of several phenomenological parameters, the populations of ionic clusters of different sizes as a function of salt concentration; it captures the onset of ionic gelation and also the post-gel partitioning of ions into the gel. We discuss the applicability of our model, as well as the implications of its predictions on thermodynamic, transport, and rheological properties.

Liquid–liquid phase separation (LLPS) is an intermediate step during the precipitation of calcium carbonate, and is assumed to play a key role in biomineralization processes. Here, we have developed a model where ion association thermodynamics in homogeneous phases determine the liquid–liquid miscibility gap of the aqueous calcium carbonate system, verified experimentally using potentiometric titrations, and kinetic studies based on stopped‐flow ATR‐FTIR spectroscopy. The proposed mechanism explains the variable solubilities of solid amorphous calcium carbonates, reconciling previously inconsistent literature values. Accounting for liquid–liquid amorphous polymorphism, the model also provides clues to the mechanism of polymorph selection. It is general and should be tested for systems other than calcium carbonate to provide a new perspective on the physical chemistry of LLPS mechanisms based on stable prenucleation clusters rather than un‐/metastable fluctuations in biomineralization, and beyond., A quantitative, general model for liquid–liquid phase separation is introduced based on “nonclassical” nucleation via prenucleation clusters. Potentiometric titrations and stopped‐flow ATR‐FTIR spectroscopy verify the predictive power of the model for the aqueous calcium carbonate system. This model reconciles the previously inconsistent literature values for the solubilities of amorphous calcium carbonates.

Complex formation between Ga(III) and 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR, H2L) was studied in a water-chloroform medium, in the presence or absence of xylometazoline hydrochloride (XMH). Optimum conditions for the extraction of Ga(III) were found. In the presence of XMH, the extracted ion-associate has the formula (XMH+)[GaIIIL2], where HTAR is in its deprotonated form L2–. Some key extraction-spectrophotometric characteristics were determined: absorption maximum (521 nm), apparent molar absorptivity (5.8 × 104 dm3 mol–1 cm–1), limit of detection (18 ng cm–3), limit of quantitation (60 ng cm–3), extraction constant (LogK = 4.44), distribution ratio (LogD = 2.2) and fraction extracted (99.3 %). In the absence of XMH, the extracted chelate contains one deprotonated and one monoprotonated HTAR: [GaIII(HL–)(L2–)]. It has an absorption maximum at 523 nm and a shoulder at 580–590 nm. The pKa of HTAR (H2L ⇄ H+ + HL– equilibrium) was calculated (5.4) and the effect of foreign ions was studied. This work is licensed under a Creative Commons Attribution 4.0 International License.

Conductance data for Et4NBr, Et4NBF4, Bu4NBr, Bu4NBF4 in acetonitrile for the molar concentration range of 2·10-4–1·10-2 mol·dm-3 over the temperature range from 5 to 55 °C are reported. Limiting molar conductivities and ion association constants were determined by using the Lee-Wheaton equation for the symmetrical electrolytes. On the basis of the preliminary conductometric data analysis it was established that the closest approach parameter is almost independent from the temperature for all studied acetonitrile solutions. Therefore, the closest approach parameter was adopted as a sum of cation and anion radii for further conductometric data treatment. The limiting conductivities of Br-, BF4-, Et4N+ and Bu4N+ ions and the structure-dynamic parameter of ion-molecular interaction obtained from the experimental data on limiting molar conductivities were evaluated in the framework of the approach proposed by authors [Kalugin O. N., Vjunnik I. N. Limiting ion conductance and dynamic structure of the solvent in electrolyte solution. Zh. Khim. Fiz. (Rus.) 1991, 10 708-714]. Elongation of the alkyl radical of the tetraalkylammonium cation from Et4N+ to Bu4N+ leads to a significant increase in the structure-dynamic parameter, which indicates the dynamic structuring of the solvent near the tetrabutylammonium ion and increased solvophobic solvation of the Bu4N+ compared to Et4N+. Ion association constants are discussed in terms of competition between Coulomb and non-Coulomb forces in terms of short-range square-mound potential. An increase in the ion association constants in the sequence Bu4NBF4

金沢大学理工研究域物質化学系, Molecular association between biocompatible dendritic polymers, dendrigraft poly-l-lysines (DGLs), and an anionic fluorescent probe, 8-anilino-1-naphthalenesulfonate (ANS-), was studied at the polarized water|1,2-dichloroethane (DCE) interface. The fluorescence intensity of ANS measured in aqueous solution was enhanced by the coexistence of DGLs over a wide pH range (2 < pH < 10), where ANS and DGL exist as a monoanionic form and a polycation, respectively. The voltammetric responses indicated that the positively charged DGLs were adsorbed at the water|DCE interface, whereas ANS- was transferred across the interface accompanied by the adsorption process. The interfacial behavior of the DGL-ANS associates was analyzed by potential-modulated fluorescence (PMF) spectroscopy. The PMF results demonstrated that the ion association between DGLs and ANS at the water|DCE interface is strongly affected by the applied potential and the dendritic generation of DGL. By applying appropriate potentials, the ANS anion was dissociated from its ion associate with DGLs at the interface and transferred into the organic phase, whereas DGLs remained in the aqueous phase. The Gibbs free energy of ion association (ΔGD···ANS) was estimated for the second-fourth generation DGLs (DGL-G2-G4) and the G4 polyamidoamine (PAMAM) dendrimer as a control. The highest stability of the DGL-G4-ANS associate manifested itself through ΔGD···ANS: DGL-G4-ANS (>G4 PAMAM dendrimer-ANS) > DGL-G3-ANS > DGL-G2-ANS. The results elucidated the efficient anion-binding ability of higher generation DGLs and its potential dependence at the liquid|liquid interface. © 2018 American Chemical Society., Embargo Periods 12 Months

In this work, we demonstrated proof-of-concept for the use of ion-selective electrodes (ISEs) as a promising tool for the assessment of total antioxidant capacity (TAC). Novel membrane sensors for 2,6-dichlorophenolindophenolate (DCPIP) ions were prepared and characterized. The sensors membranes were based on the use of either CuII-neocuproin/2,6-dichlorophenolindo-phenolate ([Cu(Neocup)2][DCPIP]2) (sensor I), or methylene blue/2,6-dichlorophenolindophenolate (MB/DCPIP) (sensor II) ion association complexes in a plasticized PVC matrix. The sensors revealed significantly enhanced response towards DCPIP ions over the concentration range 5.13 &times, 10&minus, 5&ndash, 1.0 &times, 2 and 5.15 &times, 2 M at pH 7 with detection limits of 6.3 and 9.2 &micro, g/mL with near-Nernstian slope of &minus, 56.2&plusmn, 1.7 and &minus, 51.6&plusmn, 2 mV/decade for sensors I and II, respectively. The effects of plasticizers and various foreign common ions were also tested. The sensors showed enhanced selectivity towards DCPIP over many other phenolic and inorganic ions. Long life span, high potential stability, high reproducibility, and fast response were also observed. Method validation was also verified by measuring the detection limit, linearity range, accuracy, precision, repeatability and between-day-variability. The sensors were introduced for direct determination of TAC in fresh and canned juice samples collected from local markets. The obtained results agreed fairly well with the data obtained by the standard method.

Quantifying ion association and collective dynamical processes in organic electrolytes is essential for fundamental property interpretation and optimization for electrochemical applications. The extent of ion correlation depends on both the ion concentration and dielectric strength of the solvent; ions may be largely uncorrelated in sufficiently high-dielectric solvents at low concentration, but properties of concentrated electrolytes are dictated by correlated and collective ion processes. In this work, we utilize molecular dynamics simulations to characterize ion association and collective ion dynamics in organic electrolytes composed of binary mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM^+][BF^4–] and 1,2-dichloroethane, acetone, acetonitrile, and water solvents. We illustrate different physical regimes of characteristically distinct ion correlations for the systematic range of electrolyte concentrations and solvent dielectric strengths. Dilute electrolytes composed of low-dielectric solvents exhibit significant counterion correlation in the form of ion pairing and clustering driven by both weak screening and relatively low solvation energies. This regime is characterized by enhanced ion coordination numbers and near equality of cation and anion diffusion coefficients, despite the significantly different ion sizes. In contrast, ion correlation in highly concentrated electrolytes is dominated by the anti-correlated motion of both like-charge and opposite-charge ions, approaching neat ionic liquid behavior. We show that the cross-over of these correlation regimes is clearly illuminated by quantifying the fractional self and distinct contributions to the net ionic conductivity. For organic electrolytes composed of low-dielectric solvents, we conclude that significant ion correlation exists at all concentrations but the nature of the correlation changes markedly from the dilute electrolyte to the pure ionic liquid limit.

A selective separation and recycling system for metal ions was developed by homogeneous liquid-liquid extraction (HoLLE) using a fluorosurfactant. Sixty-two different elemental ions (e.g., Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, In, Ir, La, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Os, P, Pb, Pd, Pr, Pt, Re, Rh, Ru, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Te, Ti, Tl, Tm, V, W, Y, Yb, Zn, and Zr) were examined. By changing pH from a neutral or alkaline solution (pH ≥ 6.5) to that of an acidic solution (pH &lt, 4.0), gallium, zirconium, palladium, silver, platinum, and rare earth elements were extracted at &gt, 90% efficiency into a sedimented Zonyl FSA® (CF3(CF2)n(CH2)2S(CH2)2COOH, n = 6–8) liquid phase. Moreover, all rare earth elements were obtained with superior extraction and stripping percentages. In the recycling of rare earth elements, the sedimented phase was maintained using a filter along with a mixed solution of THF and 1 M sodium hydroxide aqueous solution. The Zonyl FSA® was filtrated and the rare earth elements were recovered on the filter as a hydroxide. Furthermore, the filtrated Zonyl FSA was reusable by conditioning the subject pH.

The formation and liquid-liquid extraction of ion-association complexes between Co(II)-4-(2-Pyridylazo)resorcinol (PAR) anionic chelates and cations of three ditetrazolium chlorides were studied: Blue Tetrazolium chloride (BTC), Neotetrazolium chloride (NTC) and Nitro Blue Tetrazolium chloride (NBT). The optimum conditions for the formation and solvent extraction of the ion-association comlpex chelates were determined. It has been found that in the systems of Co(II)-PAR-DTS, the reactants are reacted in molar ratios 1:2:1 and the general formula of complexes was suggested. The extraction equilibria were investigated and quantitatively characterized by the equilibrium constants and the recovery factors. The analytical characteristics of the complexes were calculated.

International audience; We performed molecular dynamics simulations of carboxylate/methylated ammonium ion pairs solvated in bulk water and of carboxylate/methylated ammonium salt solutions at ambient conditions using an ab initio-based polarizable force field whose parameters are assigned to reproduce only high end quantum computations, at the Møller-Plesset second-order perturbation theory/complete basis set limit level, regarding single ions and ion pairs as isolated and micro-hydrated in gas phase. Our results agree with the available experimental results regarding carboxylate/ammonium salt solutions. For instance, our force field approach predicts the percentage of acetate associated with ammonium ions in CH3COO−/CH3NH3+ solutions at the 0.2–0.8M concentration scale to range from 14% to 35%, in line with the estimates computed from the experimental ion association constant in liquid water. Moreover our simulations predict the number of water molecules released from the ion first hydration shell to the bulk upon ion association to be about 2.0 ± 0.6 molecules for acetate/protonated amine ion pairs, 3.1 ± 1.5 molecules for the HCOO−/NH4+ pair and 3.3 ± 1.2 molecules for the CH3COO−/(CH3)4N+ pair. For protonated amine-based ion pairs, these values are in line with experiment for alkali/halide pairs solvated in bulk water. All these results demonstrate the promising feature of ab initio-based force fields, i.e., their capacity in accurately modeling chemical systems that cannot be readily investigated using available experimental techniques.

Complex formation of Ni(II) and 1,10-phenanthroline (C12H8N2/Phen) with the addition of dithizone (C13H12N4S/HDz) at the hexane-water interface has been studied by direct measurement spectrophotometry using the centrifugal liquid membrane (CLM) method. Ni(II) ion with Phen formed a cationic complex of Ni(C12H8N2)2 2+ or NiPhen2 2+ . That complex dissolved in the aqueous phase and had two UV absorption spectrum maxima wavelengths, λmax 270 and 292 nm. Observation of complex formation was performed variations of pH and ligand concentration. The pH caused protonation that affected the amount of the formed complex. With the variations of ligand concentrations, the greater was the concentration of ligands the greater was the formed complex. Based on the Batch method, the HDz ligand addition into the NiPhen2 2+ cationic complex produced ion association complex of Ni(C13H11N4S)2(C12H8N2) or NiDz2Phen at λmax 403 nm, and was extracted in the organic phase. Measurement results using CLM method showed that NiDz2Phen complex was formed at hexane-water interface with λmax 523 nm. Comparison of Phen with HDz ligand concentrations affected the initial formation rate of NiDz2Phen complex. The greater concentration of Phen ligand increased the initial rate of formation for synergistic complex. The obtained data using CLM method indicated that the synergistic complex formation rate constant of NiDz2Phen at the interface, k was 0.30/s.

We have measured the structure and properties of a series of dicationic quaternary ammonium compounds α,ω-bis(N-alkyl dimethyl ammonium)hexane halides (Cn-C6-Cn) for values of the alkyl chain length n of 8, 9, 10, 11, 12, and 16, and a series of α,ω-bis(N-alkyl dimethyl ammonium)diethylether halides (Cn-C2OC2-Cn) for values of n of 8, 12, and 16, as well as C8-C12-C8 and C12-C10-C12 at the air/water interface. Although the critical micelle concentration (CMC) in the two series decreases in the normal way, that is, logarithmically, with increasing chain length, the limiting surface tension at the CMC and the limiting area per molecule both increase with chain length, in the opposite direction from comparable single chain surfactants. The structures of the surface layers, which were determined by neutron reflectometry, indicate that the anomalous behavior of the surface tension and area are probably caused by poor packing of the gemini side chains between adjacent molecules. Comparison of the directly determined surface coverage using neutron reflectometry and the apparent coverage determined by application of the Gibbs equation to surface tension data gives an experimental measurement of the prefactor in the Gibbs equation, which should be 3 for these geminis. It was found to vary from about 3 for the two C16 geminis down to about 1.5 for the two C8 geminis. We have devised a simple quantitative model that explains this variation and earlier observations that the Gibbs prefactor for C12-Cn-C12 (n varying from 3 to 12) is around 2. The model is consistent with the conductivity, NMR, and fluorescence measurements of other authors. This model shows that both dimerization and ion association are required to explain the surface tension behavior of cationic gemini bromide surfactants and that, in many cases, the prefactor itself varies with concentration.

A simple extractive spectrophotometric method has been developed for the quantification of mirtazapine. This method is based on the formation of ion-association complex of mirtazapine drug with bromocresol purple dye. The absorbance of the complex was measured at 400 nm. The method was successfully applied to the determination of mirtazapine in their pharmaceutical formulations. The method shows a linear range from 0.2-10 μg mL-1 with a molar absorptivity of 1.53 '10 4 L mol-1 cm-1. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.096 μg mL-1 and 0.32μg mL-1 respectively. The developed methodology was successfully applied for the determination of mirtazapine in commercial formulation and the percentage recovery was found 99.91 ± 0.15. The developed methodology promises a feasible, low cost and an efficient method for the routine analysis.

Springer New York LLC, The amount of dietary oxalate from food may be an important risk factor in the development of idiopathic calcium oxalate nephrolithiasis. The main aim of this research was to develop an accurate and reliable method by cloud point extraction (CPE) combined with spectrophotometry to measure the oxalate contents of selected vegetables. The method is based on ion association of stable anionic complex, which is produced by the reaction of oxalate with Mo(VI), with Toluidine blue (TBH2+), and then by extraction into micelles of octylphenol ethoxylate (Triton X-45) in the presence of NH4F as a salting-out agent at pH 6.0. Using the optimized conditions, the calibration graph was highly linear in the range of 1.2–240 ?g L?1. The detection limit of the method (LOD (3?blank/m) was 0.36 ?g L?1, and the relative standard deviation (RSD %) as a measure of precision was in the range of 1.1–5.3 % (n = 5 for 5, 25, and 50 ?g L?1). The method was successfully applied to the speciative determination of soluble and total oxalate in vegetables after ultrasonic-assisted extraction and dilution at suitable ratios. The amount of insoluble oxalate was calculated from the analytical difference between total oxalate and soluble oxalate contents of samples with and without acidic extraction under ultrasonic power (300 W, 50 Hz) for 15 min at 60 °C. The accuracy of the method was intrinsically controlled and verified by comparing the results obtained with those of an independent kinetic method as well as recoveries of spiked samples. [Figure not available: see fulltext.] © 2015, Springer Science+Business Media New York., Altunay, N.; Department of Chemistry, University of CumhuriyetTurkey; email: naltunay@cumhuriyet.edu.tr

Springer New York LLC, In this article, ultrasonic-assisted cloud point extraction (UA-CPE) was used to the preconcentration of trace Ag(I) and Cd(II) in dried nut and vegetable samples. After ion association of Ag(I) and Cd(II) ions with 3,7-diamino-2,8-dimethyl-5-phenyl-phenaziniumchlorid (Safranin T) in the presence of excess potassium iodide (KI) at pH 6.0, the ternary complexes formed were quantitatively extracted into a micellar phase of poly(ethyleneglycol-mono-p-nonylphenylether) (PONPE 7.5) and then determined by flame atomic absorption spectrometry (FAAS). The matrix effects of possible some interfering ions on the method recovery and tolerance limits were also investigated. Under the optimized reagent conditions, the method was linearly dependent on the analyte concentrations in the range of 0.08–90 and 3–250 ?g L?1 with limits of detection of 0.02 and 0.9 ?g L?1 for Ag(I) and Cd(II), respectively. The reproducibility as the percent relative standard deviations (RSDs %) (0.5, 5.0, and 25 ?g L?1 for Ag(I) and 15, 30, and 100 ?g L?1 for Cd(II), n = 6) was lower than 3.6 % for both analytes. The accuracy of the method was controlled by analysis of two certified samples (SRM 1573a Tomato leaves and SRM 1643e Trace elements in waters) as well as recovery studies from spiked samples. It has been observed that the results obtained are in a good agreement with the certified values at confidence interval of 95 %. The method was successfully applied to determination of Ag(I) and Cd(II) in several dried nut and vegetable samples by FAAS after separation/preconcentration with UA-CPE. © 2016, Springer Science+Business Media New York., Altunay, N.; Faculty of Science, Department of Chemistry, University of CumhuriyetTurkey; email: naltunay@cumhuriyet.edu.tr

Neutron diffraction with isotopic substitution has been used to characterize the bulk liquid structure of the technologically relevant electrolyte solution, 1 M tetrapropylammonium bromide (TPA Br) in acetonitrile (acn), and of pure deuterated acetonitrile. Empirical potential structure refinement modeling procedures have been used to extract detailed structural information about solvent-solvent, solvent-ion, and ion-ion correlations. Analysis of the refined data shows the expected local dipolar conformation of acn in the pure solvent. This short-range dipolar ordering is also present within the solutions of TPA Br in acn, and it affects how the solvent orders itself around the ions. The solvation numbers of the TPA cations and the bromide anions are deduced, 8 and 5, respectively, as are the orientations of the solvent molecules that surround the ions. Evidence for ion association is also presented, with nearly two-thirds of the ions in the system being in associated pairs or clusters.

Two simple and rapid titrimetric methods are described for the determination of bupropion hydrochloride (BUPH) in pharmaceuticals. The proposed methods are based on the solvent extraction-titration of BUPH with two ion-association reagents, i.e. sodium lauryl sulphate (SLS) and tetraphenylborate (TPB). In method A, SLS was used as titrant and the titration was carried out in the presence of dilute sulphuric acid and chloroform using dimethyl yellow as indicator whereas in method B, the titrant was TPB and the titration was done in borate-phosphate buffer of pH 6.0 and 1,2-dichloroethane with tetrabromophenolphthalein ethyl ester (TBPE) as indicator. In the two-phase titrations, the proposed procedures give sharp end points as the color of the organic phase changes from yellow to pink in method A and from red-violet to yellow in method B. The methods are applicable over the ranges of 1.0-20.0 and 3.0-10.0 mg of BUPH for method A and method B, respectively. The accuracy and precision of the methods are good. The methods were applied successfully to the determination of BUPH in tablets and the results were in agreement with the label claim and those of the comparison method.

A simple ion pair-dispersive liquid-liquid microextraction method was proposed for preconcentration trace amounts of rhodium. An ion association complex of RhCl4- and tetradecyldimetylbenzylamonium was extracted into cholorobenzene. The volume and the type of extractive and dispersive solvents, the extraction time and the pH of the aqueous solutions were optimized. The calibration curve was linear in the range of 0.6-500 ng mL-1 of rhodium. The limit of detection was 0.10 ng mL-1 in initial solution and preconcentration factor was 40. The proposed method was successfully applied to the extraction and determination of rhodium in road dust and water samples.