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Abstract: Two-step stacking of organic cations by sweeping and micelle to solvent stacking (MSS) in capillary zone electrophoresis (CZE) is presented. The simple procedure involves hydrodynamic injection of a micellar sodium dodecyl sulfate solution before the sample that is prepared without the micelles. The micelles sweep and transport the cations to the boundary zone between the sample and CZE buffer. The presence of organic solvent in the CZE buffer induces the second stacking step of MSS. The LODs obtained for the four beta blocker and two tricyclic antidepressant test drugs were 20–50 times better compared to typical injection. [ABSTRACT FROM AUTHOR]

Abstract  The thermodynamic functions of complex formation of benzo-15-crown-5 ether (B15C5) and sodium cation (Na+) in the mixtures of propan-1-ol (PrOH) with water at 298.15 K have been calculated from experimental measurements. The equilibrium constants of B15C5/Na+ complex formation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by a calorimetric method. The complexes are enthalpy stabilized but entropy destabilized in the PrOH–H2O mixtures. The effects of preferential solvation of B15C5 by molecules of the organic solvent, solvation of the sodium cation, as well as the acid-base properties of propan-1-ol–water mixtures on the complex formation processes are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Cationic corn starch derivatives with a high degree of substitution are prepared in alkaline solution or in mixed media of organic solvent and water with different levels of the cationic reagent, 2,3-epoxypropyltrimethylammonium chloride. The starch cationization yield is investigated, and the results indicate that the degree of substitution (DS) of the samples depends on the reaction conditions and reaction media. The maximum DS values are up to 1.37 in 1,4-dioxane alkaline–aqueous solution. Meanwhile, the structures of the cationic starch derivatives are characterized by elemental analyses, FTIR spectroscopy, X-ray diffraction, and 13C NMR spectroscopy, as well as by SEM techniques. [Copyright &y& Elsevier]

A silver- and Brönsted acid-free protocol for generating the (tricy- clohexylphosphine)gold(l) cation from the corresponding azide complexes is disclosed. The gold(l) cations so liberated are trapped by complexation with octaethylporphyrin. The first structurally authenticated gold(l) porphyrin complex crystallizes with formula C72H112Au2F12N4P2Sb2, space group (2/c, a = 21.388(4), b = 19.679 (4), c = 19.231(3) Å; β = 111.030 (3)°. Solution spectroscopic studies indicate that the di-gold complex fragments on dissolution in organic solvents. Approximate density-functional theory calculations find an electrostatic origin for the binding of two gold(I) centers to the unprotonated nitrogen atoms, despite greater orbital density on the porphyrin meso carbons. [ABSTRACT FROM AUTHOR]

Abstract: Densities of LiCl, NaCl, KCl, and CsCl in normal and heavy water solutions have been measured using a vibrating-tube densitometer with (1–2)·10−6 precision at T =(288.15, 298.15, and 308.15)K over a wide concentration range from (0.1 to 5) molal, m. Solvent isotope effects (IE) on apparent molar volumes, as well as both on solute- and solvent-partial molar volumes were evaluated to establish their trend with cationic size in a systematic way. With the exception of the LiCl, both the “normal” standard IEs, , and the “inverse” excess IEs of the solutes, , increase linearly with the electrostriction effect of the cations (1/r ion), while with increasing temperature and/or concentration, the excess effects become almost the same. In contrast to the solute excess IEs, which show linear m 1/2-dependence over the whole concentration range, except for LiCl, the “inverse” excess IEs of the solvent, , hardly change over the lower concentration range (, m ⩽1). However, with further increase of the concentration, these IEs significantly decrease. Individual ionic standard and excess volume contributions are derived and the results are discussed in terms of structural concepts of ionic hydration. [Copyright &y& Elsevier]

Solvation of a calix[4]resorcinarene and its anions in water-organic media of varying composition was characterized by solubility measurements, acid-base titration and X-ray structural analysis. Methanol, 2-propanol, and DMSO capable of developing calix[4]resorcinarene solvated complexes of varying structure and stability were used as the organic component. It was revealed that the influence of the organic component of water-organic solvents on the stability of guest-host complexes formed by some organic and complex cations with calix[4]resorcinarene anions depended on the structure of the complexes. [ABSTRACT FROM AUTHOR]

Copolyethers and polyurethanes containing lower and upper rim calix[4]arene units in the fixed cone conformation were prepared in good yield by polycondensation reactions of distal calix[4]arene diols with bisphenol-A/dibromomethane and 2,4-tolylendiisocyanate (TDI), respectively. In a similar way were prepared calix[4]arene-crown-5 and -crown-6 polyurethanes in the fixed 1,3-alternate conformation by condensation of TDI with lower rim calixcrown-5 and calixcrown-6 diols. However, the poor solubility in common organic solvents of the copolyether derivatives (Mw=11,100–11,600 g/mol) hampered further studies on their ionophoric properties. Aiming to obtain model compounds for the investigation of both extraction abilities and ionophoric properties of the polyurethane materials, several bis-urethanes were also synthesized by reaction of the calix[4]arene diols with p-tolylisocyanate (TI). The extraction ability measurements of monomeric and polymeric calix[4]arene urethanes (Mw=12,300–83,500 g/mol) towards alkali metal cations (Li+, Na+, K+, Rb+, Cs+) and Ag+showed a remarkable efficiency and selectivity of calixcrown-6 polyurethane toward Rb+, Cs+and Ag+. [Copyright &y& Elsevier]

The effect of dielectric and chemical (donor-acceptor interactions, cohesion energy density) properties of aqueous-organic solvents (water-methanol, water-2-propanol, water-acetonitrile, water-acetone, water-dioxane) on the thermodynamic functions of complexation of sodium and potassium cations with 18-crown-6 ether at 298 K was subjected to overall correlation analysis. [ABSTRACT FROM AUTHOR]