有机铵盐对FC-SAA表面活性及溶度的影响

测定了一系列有机铵盐与一种全氟烷磺酸盐１：１混合体系水 溶液的表面张力，由此研究有机铵盐对碳氟表面活性剂表面活性及溶度的影响，导出应用于此种混合体系的Ｇｉｂｂｓ吸附公式，并讨论了混合体系中两表面活性组分的表面分子相互作用和表面层的结构。     

Intrinsic Surface Reaction Constant in 1-pK Model of Mg-Fe Hydrotalcite-like Compounds

The relationship among intrinsic surface reaction constant (K) in 1-pK model, point of zero net charge (PZNC) and structural charge density (σst) for amphoteric solid with structural charges was established in order to investigate the effect of σst on pK. The theoretical analysis based on 1-pK model indicates that the independent PZNC of electrolyte concentration (c) exists for amphoteric solid with structural charges. A common intersection point (CIP) should appear on the acid-base titration curves at different c, and the pH at the CIP is pHPZNC. The pK can be expressed as pK=-pHPZNC log[(1 2αPZNC)/(1-2αPZNC)], where αPZNC≡σst/eNANs, in which e is the elementary charge, NA the Avogadro‘s constant and Ns the total density of surface sites. For solids without structural charges, pK=-pHPZNC. The pK values of hydrotalcite-like compounds (HTlc) with general formula of [Mg1-xFex(OH)2](Cl,OH)x were evaluated. With increasing x, the pK increases, which can be explained based on the affinity of metal cations for H^- or OH^- and the electrostatic interaction between charging surface and H^- or OH^-.     

New Type of an Adsorption Layer of Organic Molecules with a Cage Structure Condensed at the Electrode/Solution Interface: The Adsorption of Cubane Derivatives on a Mercury Electrode

A synthesis and a study by method of measuring the differential capacitance on a stationary mercury drop of the adsorption of a number of cubane derivatives in a surface-inactive electrolyte are performed. It is established that the compounds studied exhibit a high surface activity. For bromine derivatives of cubane (4-bromomethoxycarbonylcubane, 4-bromohydroxymethylcubane) the formation of two-dimensional adsorption layers is discovered. Values of adsorption parameters for these compounds are evaluated with use made of the Frumkin isotherm.     

Potential distribution across membranes with surface-charge layers. Effects of ionic solubility

A model is presented for the potential distribution across a charged membrane. The membrane-fixed charges are assumed to be distributed through a surface layer of non-zero thickness on the membrane. We treat the surface layer as a different phase from the surrounding solution phase. The potential arises from the membrane-fixed charges and from different solubilities of positive and negative electrolyte ions in the two phases. Equations are presented for the potential distribution, which involve the partition coefficients of electrolyte ions and the relative permittivity of the surface layer.     

Diffusion layer titration of dipyrone in pharmaceuticals at a dual-band electrochemical cell

This paper describes the use of a thin-layered dual-band electrochemical cell operating at flow conditions to determine dipyrone (sodium salt of 1-phenil-2,3-dimethyl-4-methylaminomethanesulfonate-5-pyrazolone) by reaction with electrogenerated iodine. The electrolytic cell consisted of two closely spaced gold electrodes, the upper stream electrode serving as the generator electrode and the downstream electrode working as the collector electrode. A linear dynamic range from 2 to 15 μmol l⁻¹ dipyrone was obtained by using a sample volume of 100 μl, with a detection limit of 1.1 μmol l⁻¹. Standard deviation (S.D.) of 3.4% for 20 repetitive injections of a 40 μmol l⁻¹ dipyrone solution and sampling frequency of 90 h⁻¹ were achieved. The results obtained with the thin-layered dual-band electrochemical cell for dipyrone determination in three different pharmaceutical samples compared well with those found by iodimetry with coulometrically generated iodine.     

The disorderly exfoliated LDHs/PMMA nanocomposites synthesized by in situ bulk polymerization: The effects of LDH-U on thermal and mechanical properties

The disorderly exfoliated layered double hydroxides/poly(methyl methacrylate) (LDHs/PMMA) nanocomposites were obtained in a two-stage process by the in situ bulk polymerization of methyl methacrylate (MMA) in the presence of 10-undecenoate intercalated LDH (LDH-U). The dispersed behavior of the LDH-U in the PMMA matrix was identified by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV/visible transmission spectroscopy. All these nanocomposites showed significantly enhancement of glass transition temperature (T_g) and the decomposition temperatures compared to pristine PMMA, as identified in differential scanning calorimetry (DSC) and thermogravimetric (TGA) analysis. The tensile modulus of these nanocomposites was also enhanced by incorporating the LDH-U into the PMMA matrix and increased as the amount of LDH-U increased. According to the analytical method of Ozawa-Flynn, the degradation activation energies of these nanocomposites are higher than that of pristine PMMA.     

Double Pore Silica Gel Monolith Applied to Liquid Chromatography

Silica gels retaining double pore structure in the size ranges of micrometer and nanometer have been applied to the rod-shaped monolithic column for liquid chromatography. The macropore structure was designed by controlling the phase separation process induced by the hydrolysis and polycondensation of alkoxysilane, whereas the mesopore structure was tailored by the solvent exchange treatments on wet gels. The size exclusion chromatograms on polystyrene standards exhibited almost similar features for octadecyl-modified rod and conventional packed beads columns. The dependence of plate height on the velocity of mobile phase determined for amylbenzene was by far weaker in the rod column than in the packed beads column, suggesting that additional geometrical factors should be considered in describing the separation mechanism in the rod column.     

The use of silicon in the preparation of apolar glass capillary columns

As an extention of previous reports, variables affecting the performance of columns modified by silicon deposition have been optimized. The aim of this work was to produce thermostable apolar glass capillary columns regardless of the glass type used and to maintain column performance under stressful conditions. The main parameters studied were the influence of glass type, leaching effects, and silicon layer thickness on column activity. Deactivation and stationary phase conditions were held constant. Both coated and uncoated columns were tested. The thickness of the silicon layer was found to be relatively unimportant. There was no difference whether soft glass or borosiiicate glass was used and leaching before silicon deposition did not influence column activity. Bare silicon surfaces showed considerable activity especially in respect to interactions with free acids and bases. There are indications that the surface consists of silicon oxide and other oxygenated forms of silicon rather than of the element. Treatment of the silicon layers with dilute hydrofluoric acid and the strict exclusion of traces of oxygen and water did not improve the situation. In spite of such specific interactions, silicon surfaces were easily deactivated by heat treatment with polysiloxanes. Silicon surfaces deactivated by baking with octamethyltetrasiloxane at 400°C are inert and temperature stable and show characteristics similar to persilylated surfaces.     

Non-aqueous,reversed-phase,high-performance,thin-layer chromatography and column liquid chromatography of metal complexes of porphine

Summary The chromatographic mobility of 21H, 23H-porphine and its Ni(II), Cu(II), Zn(II) and Pd(II) complexes were investigated by high-performance thin-layer chromatography on an octadecyl-bonded, silica gel plate with various polar organic solvents including alcohols, acetonitrile, dimethylsulfoxide and propylenecarbonate. The mobility generally decreases according to the central metal ion of the complex as follows: Zn(II)>(free porphine)>Ni(II)>Pd(II)>Cu(II). Methanol is a good choice of solvent for the separation of these metal porphine complexes. Successful separation of porphine and the four metal complexes is accomplished within 13 min on a LiChrosorb RP-18 column with methanol eluent.     

Morphogenetic control of calcite crystal growth in sulfonic acid based hydrogels

In this paper the mineralization of CaCO(3) in various hydrogel matrices is presented. Sulfonic acid based hydrogels were prepared by introduction of sulfonate-containing monomers into a polyacrylamide network. The sulfonate content of polyacrylamide-co-vinylsulfonate and polyacrylamide-co-allylsulfonate decreases during elution of the copolymers in demineralized water, indicating insufficient linking of the sulfonate-bearing monomers within the hydrogel. In contrast to this, acrylamidomethylpropanesulfonate (AMPS) effectively copolymerizes with acrylamide (AAm) monomers. To study the influence of spatial arrangement of ionic functional groups within hydrogel networks on the mineralization of CaCO(3), AMPS copolymers with different degrees of AMPS cross-linking were synthesized. For the mineralization experiments the copolymers were placed into a double-diffusion arrangement. Calcite as the thermodynamically stable modification of CaCO(3) was obtained with a particular morphology. The pseudocubic habitus resembles aggregates obtained by mineralization in pure polyacrylamide. However, closer examination of the aggregates by scanning electron microscopy (SEM) shows that the crystal growth in the AMPS copolymers is different from that observed in polyacrylamide. Whereas the morphology of the calcite aggregates could be fine-tuned by using copolymers with different sulfonate content, the spatial distribution of the ionic functional groups alters the course of crystallization. Calcium ions are locally accumulated due to the heterogeneous distribution of functional sulfonate groups within the copolymer network. Thereby the nucleation of calcite is triggered, resulting in enhanced mineralization.