Use of gas-liquid chromatography for analyzing products of carbonylation of certain pyridine bases

A method has been elaborated for the quantitative gas-chromatographic analysis of a mixture of piperidine, N-formylpiperidine, and pyridine on polyethylene glycol-4400 applied onto a chromosorb and NaCl, and apezon L, applied onto NaCl. The relative retentive volumes and heats of solution of the components of the mixture were calculated.     

Direct and Rapid Detection of Diphtherotoxin via Potentiometric Immunosensor Based on Nanoparticles Mixture and Polyvinyl Butyral as Matrixes

In this paper a novel potentiometric immunosensor for direct and rapid detection of diphtherotoxin (D‐Ag) has been developed by means of self‐assembly of monoclonal diphtheria antibody (D‐Ab) onto a platinum electrode based on nanoparticles mixture (containing gold nanoparticles and silica nanoparticles) and polyvinyl butyral (PVB) as matrixes. At first, D‐Ab was absorbed onto the surface of nanoparticles mixture, and then they were entrapped into polyvinyl butyral sol‐gel network on a platinum electrode. The detection is based on the change in the potentiometric response before and after the antigen‐antibody reaction in a phosphate buffer solution (pH 7.0). The immobilized D‐Ab exhibited direct potentiometric response toward D‐Ag. In comparison to the conventional applied methods, this strategy could allow antibodies immobilized with higher loading amount and better retained immunoactivity, as demonstrated by potentiometric response, cyclic voltammetry and electrochemical impedance spectroscopy of the immunosensor. The immunosensor with nanoparticles mixture exhibited much higher sensitivity, better reproducibility, and long‐term stability than that with gold nanoparticles or silica nanoparticles alone. The linear range was from 5.0×10^?3 to 1.2 μg?mL^?1 with a detection limit of 1.1×10^?3 μg?mL^?1. Up to 16 successive assay cycles with retentive sensitivity were achieved for the probes regenerated with in 0.2 mol?L^?1 glycine‐hydrochloric acid (Gly‐HCl) buffer solution and 0.25 mol?L^?1 NaCl. Moreover, the immunosensor with nanoparticles mixture was applied to evaluate a number of practical specimens with potentiometric results in acceptable agreement with those given by the ELISA method, implying a promising alternative approach for detecting diphtherotoxin in the clinical diagnosis.     

Rapid and sensitive detection of pesticides by surface-enhanced Raman spectroscopy technique based on glycidyl methacrylate-ethylene dimethacrylate (GMA-EDMA) porous material

A novelmethod of fast and sensitive SERS detection using GMA-EDMA porous material combined with a miniature device was reported in this study. A 100 μL solution containing sample, silver colloid and NaCl was evenly mixed to ensure the sample molecules would adsorb onto silver nanoparticles. Then the mixture was added onto the porous material surface slowly, so that the aggregation of silver colloid would stay on the surface while the liquid components would flow away. This technology can improve the sensitivity of SERS detection. By this method, two pesticides tricyclazole and paraquat were successfully detected at concentrations of 5×10-3 mg/L and 1×10-3 mg/L, respectively.     

Thermodynamic studies on thin liquid films. III: Miscibility in adsorbed films at film interfaces

Thermodynamic treatment of surfactant mixture was developed for the adsorption at interfaces of thin liquid films and applied to the study of the foam film stabilized by decyl methyl sulfoxide (DeMS) in the presence of NaCl. The total surface density of NaCl and DeMS and the mole fraction of DeMS in the adsorbed film at the film surface were numerically evaluated by applying thermodynamic equations to the film tension as a function of the total molality of NaCl and DeMS and the mole fraction of DeMS in the mixture. Miscibility of NaCl and DeMS at the film surface was clarified by a phase diagram of adsorption and compared with that at the meniscus adjacent to the foam film. Judging from a phase diagram of phase transition, the transition in the DeMS foam film between common black and Newton black films, observed in part II, is a negative azeotropic transformation caused by the attractive interaction between the head group of DeMS molecule and Na⁺ or Cl^– in the adsorbed film.     

Thermodynamic studies on thin liquid films. II. Foam film stabilized by decyl methyl sulfoxide

Thermodynamic equations in Part I of this series were extended so as to be applicable to electrolyte mixtures and the resultant equations were applied to the experimental results of a NaCl-decyl methyl sulfoxide (DeMS) mixture. Film thickness and contact angle of the black foam film stabilized by DeMS were measured as a function of the total molality of NaCl and DeMS at constant mole fraction of DeMS in the mixture under constant disjoining pressure. Newton black film was observed only above a certain DeMS concentration and the phase transition between common black and Newton black films took place twice as NaCl concentration increased at constant DeMS concentration. The surface densities of NaCl and DeMS at the film surface and the differences in the surface densities between the adsorbed films at the film surface and bulk one coexisting at equilibrium were numerically evaluated by applying the thermodynamic equations to the film tension obtained from the contact angle. The film states and phase transitions were clarified in terms of the film thickness and surface densities.     

Polymer-surfactant Interactions

Aqueous solutions containing poly(vinyl-pyrrolidone) and sodium caprylate, or poly(vinyl-pyrrolidone) and tetraethylammonium perfluorooctanesulfonate,respectively, have been investigated by volumetric, ionic conductivity and surface tension methods. The presence of an interaction region has been determined from conductivity and surface tension. The width of such a region depends on the amount of polymer in the mixture,temperature, surfactant content and added electrolyte (NaCl). The observed behaviour was explained in terms of the combined effects played by the alkyl-chain hydophobicity, polar head group(s) and counter-ions. An approximate solution to a mass action model for the binding of surfactants onto polymers has been introduced. It allows determining the width of the interaction region as a function of polymer mass percent in the mixture. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of the Head Group of Surfactant on the Miscibility of Sodium Chloride and Surfactant in an Adsorbed Film and Micelle

The thermodynamic treatment of a surfactant mixture was applied to the mixture of sodium chloride, NaCl, with octyl methyl sulfoxide (OMS) and that with decyldimethylphosphine oxide (DePO). The surface tension of aqueous solutions of the mixtures was measured as a function of the total concentration and the composition of the mixtures at 298.15 K. The total surface densities of the mixtures and the composition of the adsorbed films and micelles were evaluated by applying thermodynamic equations to the expeimental results. It was found that the adsorbed film and micelle are almost composed of the surfactant and there is slight attractive interaction between the ions of NaCl and the head groups of OMS and DePO molecules in the adsorbed films and micelles. A difference in the miscibility of NaCl and surfactant was observed between the OMS and DePO systems and attributed to the difference in the hydration of the head group between OMS and DePO molecules. The comparison of these results with those of the mixtures of NaCl with tetraethylene glycol monooctyl ether (C(8)E(4)) and dodecylammonium chloride (DAC) indicated that the small difference in the miscibility in an adsorbed film and micelle among these nonionic surfactant systems arises from the difference in hydration and structure of the head groups and the large one between the nonionic surfactant and DAC systems results from electrostatic interactions between dodecylammonium and sodium ions. Copyright 2001 Academic Press.     

The perchlorate anion is more effective than the trifluoroacetate anion as an ion-pairing reagent for reversed-phase chromatography of peptides

The addition of salts, specifically sodium perchlorate (NaClO4), to mobile phases at acidic pH as ion-pairing reagents for reversed-phase high-performance liquid chromatography (RP-HPLC) has been generally overlooked. To demonstrate the potential of NaClO4 as an effective anionic ion-pairing reagent, we applied RP-HPLC in the presence of 0-100 mM sodium chloride (NaCl), sodium trifluoroacetate (NaTFA) or NaClO4 to two mixtures of synthetic 18-residue peptides: a mixture of peptides with the same net positive charge (+4) and a mixture of four peptides of +1, +2, +3 and +4 net charge. Interestingly, the effect of increasing NaClO4 concentration on increasing peptide retention times and selectivity changes was more dramatic than that of either NaCl or NaTFA, with the order of increasing anion effectiveness being Cl- < TFA- < C104-. Such effects were more marked when salt addition was applied to eluents containing 10 mM phosphoric acid (H3PO4) compared to 10 mM trifluoroacetic acid (TFA) due to the lesser starting anion hydrophobicity of the former mobile phase (containing the phosphate ion) compared to the latter (containing the TFA- ion).     

Miscibility of sodium chloride and decyl methyl sulfoxide in the adsorbed film and micelle

The surface tension of aqueous solutions of a sodium chloride (NaCl)-decyl methyl sulfoxide (DeMS) mixture was measured as a function of the total molality of the mixture and the mole fraction of DeMS in the mixture at 298.15 K under atmospheric pressure. The total surface density of the mixture and the mole fraction of DeMS in the adsorbed film and micelle were numerically evaluated by applying the thermodynamic treatment of surfactant mixture to the NaCl-DeMS mixture. Miscibility of NaCl and DeMS in the adsorbed film and micelle was clarified by use of the phase diagram of adsorption and micelle formation. Positive adsorption of NaCl was observed in the presence of DeMS and attributed to attractive interaction between the polar head group of DeMS molecule and Na+ or Cl- ions in the adsorbed film and micelle. The results were compared with those of NaCl-octyl methyl sulfoxide and NaCl-decyldimethylphosphine oxide mixtures to elucidate the structure effect of nonionic surfactant on the miscibility.     

Miscibility of sodium chloride and ionic surfactant in adsorbed film and aggregate

The adsorption, micelle formation, and salting-out of dodecylammonium chloride in the presence of NaCl were studied from the viewpoint of mixed adsorption and aggregate formation. The surface tension of aqueous solutions of a NaCl–dodecylammonium chloride mixture was measured as a function of the total molality and composition of the mixture. Judging from phase diagrams of mixed adsorption and aggregate formation, NaCl and dodecylammonium chloride are miscible in the adsorbed film and coagel particle at high NaCl concentrations due to specific (nonelectrostatic) interaction between dodecylamonium ion and the counterion, while they are immiscible in the micelle. The difference in miscibility among the oriented states was ascribed to the difference in geometry among the states and to the interaction between bilayers in a coagel particle. Miscibility and specific interaction are compared between the mixtures of NaCl with dodecylammonium chloride and sodium dodecylsulfate.     

Adsorption of Co, Ni, Cu, and Zn on hydrous manganese dioxide from complex electrolyte solutions resembling sea water in major ion content

Adsorption of Co, Ni, Cu, and Zn onto a poorly crystalline hydrous manganese dioxide (delta-MnO2) has been studied in complex electrolyte solutions such as (a) 0.5 M NaCl+0.054 M MgCl2, (b) 0.5 M NaCl+0.028 M Na2SO4, and (c) artificial sea water prepared according to the standard literature method. These three solutions allow us to identify the specific effect of major cations, major anions, and the mixture of major cations and anions (including carbonate and bicarbonate) that is present in real sea water. The adsorption isotherm in major ion sea water at pH 7.25 indicates that while Co and Zn exhibit increases in adsorption with increase in concentration, Ni shows relatively poor adsorption, reaching a plateau at 0.075 mM concentration. The three trace metals (Co, Ni, and Zn) show Langmuirian behavior for adsorption at low concentration. It is generally observed that the fractional adsorption vs pH curve shifts to higher pH either in the presence of 0.054 M MgCl2 or in sea water. In the presence of 0.028 M Na2SO4 the fractional adsorption vs pH curve remains almost unchanged with respect to a 0.5 M NaCl solution. The competitive adsorption of one trace metal in the presence of other three in major ion sea water indicates that this phenomenon is more predominant with Ni and Zn than with Co and Cu.     

Controllable gelation of methylcellulose by a salt mixture

The effects of a salt mixture consisting of a salt-out salt (NaCl) and a salt-in salt (NaI) on the sol-gel transition of methylcellulose (MC) in aqueous solution have been studied by means of micro differential scanning calorimetry and rheometry. The salt mixture was found to have a combined effect from the salt-out and salt-in salts in the mixture, and the salt effect was dependent on the water hydration abilities of the component ions and ion concentration. At a fixed total salt concentration, the sol-gel transition temperature nicely followed a rule of mixing: Tp = m1Tp1 + m2Tp2 where Tp, Tp1, and Tp2 are the gelation peak temperatures for the MC solutions with a salt mixture, NaCl, and NaI, respectively, and mi is the molar fraction of the salt component i in the salt mixture. The linear rule of mixing proved that the effects of NaCl and NaI on the sol-gel transition of MC are completely independent. In addition, the presence of a single salt or a salt mixture in a MC solution does not change the essential mechanism of MC gelation. Therefore, the sol-gel transition of MC can be simply controlled by a salt mixture consisting of a salt-out salt and a salt-in salt. The rheological results supported the micro thermal results excellently. But the gel strength of MC containing salts was influenced by both salt type and salt concentration.     

The Formation and Salt Induced Melting of a Highly Viscoelastic Mixture of Two Oppositely Charged Polyelectrolytes

A quick and convenient route to prepare a highly viscoelastic mixture of two oppositely charged polyelectrolytes is presented. The investigation was essentially performed at a fixed total polyelectrolyte concentration. The phase behaviour was studied at varying ratios between the two oppositely charged polyions. The mixtures phase separated associatively at mixing ratios in the vicinity of overall charge neutrality, while by screening the attractive forces with NaCl the precipitate could be dissolved. At certain mixing ratios off charge neutrality the mixtures were highly viscoelastic single-phase solutions in the absence of screening electrolyte. When NaCl was added to such a solution the viscoelasticity decreased strongly since the attractive forces between the oppositely charged polyions were screened. Therefore, by contacting an initially salt free mixture of polyions with a brine solution of known concentration, the diffusion of salt into the polyion matrices could be monitored by following the rheology of the mixture as a function of the contact time. It is shown that the transport of NaCl inside the polyion matrices was diffusion controlled.     

High concentrations of sodium chloride facilitate the use of immobilized chymotrypsin for separating virgin forms of specific trypsin inhibitors.

It has been shown that specific trypsin inhibitors exhibit also antichymotrypsin activity in the presence of high NaCl concentrations. Taking advantage of this phenomenon a simple procedure of separation of the virgin forms of trypsin inhibitors from squash seeds and porcine pancreas (Kazal) was elaborated. In a typical experiment the inhibitor sample was loaded onto immobilized chymotrypsin equilibrated with 5 M NaCl at pH 8. After washing out unadsorbed material the virgin forms of inhibitors could be eluted either with water, buffer pH 8.0 or 0.02 M citrate buffer pH 2.6 containing no NaCl.     

Infrared optical constants of crystalline sodium chloride dihydrate: application to study the crystallization of aqueous sodium chloride solution droplets at low temperatures

Complex refractive indices of sodium chloride dihydrate, NaCl·2H(2)O, have been retrieved in the 6000-800 cm(-1) wavenumber regime from the infrared extinction spectra of crystallized aqueous NaCl solution droplets. The data set is valid in the temperature range from 235 to 216 K and was inferred from crystallization experiments with airborne particles performed in the large coolable aerosol and cloud chamber AIDA at the Karlsruhe Institute of Technology. The retrieval concept was based on the Kramers-Kronig relationship for a complex function of the optical constants n and k whose imaginary part is proportional to the optical depth of a small particle absorption spectrum in the Rayleigh approximation. The appropriate proportionality factor was inferred from a fitting algorithm applied to the extinction spectra of about 1 μm sized particles, which, apart from absorption, also featured a pronounced scattering contribution. NaCl·2H(2)O is the thermodynamically stable crystalline solid in the sodium chloride-water system below the peritectic at 273.3 K; above 273.3 K, the anhydrous NaCl is more stable. In contrast to anhydrous NaCl crystals, the dihydrate particles reveal prominent absorption signatures at mid-infrared wavelengths due to the hydration water molecules. Formation of NaCl·2H(2)O was only detected at temperatures clearly below the peritectic and was first evidenced in a crystallization experiment conducted at 235 K. We have employed the retrieved refractive indices of NaCl·2H(2)O to quantify the temperature dependent partitioning between anhydrous and dihydrate NaCl particles upon crystallization of aqueous NaCl solution droplets. It was found that the temperature range from 235 to 216 K represents the transition regime where the composition of the crystallized particle ensemble changes from almost only NaCl to almost only NaCl·2H(2)O particles. Compared to the findings on the NaCl/NaCl·2H(2)O partitioning from a recent study conducted with micron-sized NaCl particles deposited onto a surface, the transition regime from NaCl to NaCl·2H(2)O is shifted by about 13 K to lower temperatures in our study. This is obviously related to the different experimental conditions of the two studies. The partitioning between the two solid phases of NaCl is essential for predicting the deliquescence and ice nucleation behavior of a crystalline aerosol population which is subjected to an increasing relative humidity.     

A new approach to studying aqueous reactions using diffuse reflectance infrared Fourier transform spectrometry: application to the uptake and oxidation of SO2 on OH-processed model sea salt aerosol

Diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) is a powerful technique for analyzing solid powders and for following their reactions in real time. We demonstrate that it can also be applied to studying the uptake and reactions of gases in liquid films. Within the DRIFTS cell, a 10%(w/w) mixture of MgCl(2) x 6H(2)O in NaCl was equilibrated with air at 50% RH, which is above the deliquescence point of the magnesium salt but below that of NaCl. This mixture of NaCl coated with an aqueous magnesium chloride solution was then reacted with gas phase OH to generate hydroxide ions via a previously identified interface reaction. This treatment, hereafter referred to as OH-processing, was sufficient to convert some of the magnesium chloride to Mg(OH)(2) and Mg(2)(OH)(3)Cl x 4H(2)O, making the aqueous film basic and providing a reservoir of alkalinity. Subsequent addition of SO(2) to the basic processed mixture resulted in its uptake and conversion to sulfite which was measured by FTIR. The sulfite was simultaneously oxidized to sulfate by HOCl/OCl(-) that was formed in the initial OH-processing of the salt. Further uptake and oxidation of SO(2) in the aqueous film took place when the salt was subsequently exposed to O(3). These studies demonstrate that DRIFTS can be used to study the chemistry in liquid films in real time, and are consistent with the hypothesis that the reaction of gaseous OH with chloride ions generates alkalinity that enhances the uptake and oxidation of SO(2) under these laboratory conditions.     

Polyelectrolyte modified solid surfaces: the consequences for ionic and mixed ionic/nonionic surfactant adsorption

This paper describes how the cationic polyelectrolyte, polyDMDAAC (poly(dimethyl diallylammonium chloride)), is used to manipulate the adsorption of the anionic surfactant SDS and the mixed ionic/nonionic surfactant mixture of SDS (sodium dodecyl sulfate)/C(12)E(6) (monododecyl hexaethylene glycol) onto the surface of hydrophilic silica. The deposition of a thin robust polymer layer from a dilute polymer/surfactant solution promotes SDS adsorption and substantially modifies the adsorption of SDS/C(12)E(6) mixtures in favor of a surface relatively rich in SDS compared to the solution composition. Different deposition conditions for the polyDMDAAC layer are discussed. In particular, at higher solution polymer concentrations and in the presence of 1 M NaCl, a thicker polymer layer is deposited and the reversibility of the surfactant adsorption is significantly altered.     

Electrowetting of aligned carbon nanotube films

Electrowetting is one approach to reducing the interfacial tension between a solid and a liquid. In this method, an electrical potential is applied across the solid/liquid interface which modifies the wetting properties of the liquid on the solid without changing the composition of the solid and liquid phases. Electrowetting of aligned carbon nanotube (CNT) films is investigated by the sessile drop method by dispensing deionized (DI) water or 0.03 M NaCl droplets (contacted by Au wire) onto aligned CNT films assembled on a copper substrate. The results demonstrate that electrowetting can greatly reduce the hydrophobicity of the aligned CNTs; the contact angle saturation for DI water and 0.03 M NaCl droplets occurs at 98 and 50 degrees , respectively. The combined effects of the geometrical roughness and the electrical potential on the contact angle are briefly discussed and modeled. Such a strategy may be invoked to controllably reduce the interfacial tension between carbon nanotubes (CNTs) and polymer precursors when infiltrating the monomers into the prealigned nanotube films.     

Mixed adsorption of poly(vinylpyrrolidone) and sodium dodecylbenzenesulfonate on kaolinite

The mixed adsorption of the nonionic polymer poly(vinylpyrrolidone) (PVP) and the anionic surfactant sodium dodecylbenzenesulfonate (SDBS) on kaolinite has been studied. Both components adsorb from their mixture onto the clay mineral. The overall adsorption process is sensitive to the pH, the electrolyte concentration, and the amounts of polymer and surfactant. Interpretation of the experimental data addresses also the patchwise heterogeneous nature of the clay surface. In the absence of PVP, SDBS adsorbs on kaolinite by electrostatic and hydrophobic interactions. However, when PVP is present, surfactant adsorption at 10(-2) M NaCl is mainly driven by charge compensation of the edges. The adsorption of PVP from the mixture shows similar behavior under different conditions. Three regions can be distinguished based on the changing charge of polymer-surfactant complexes in solutions with increasing SDBS concentration. At low surfactant content, PVP adsorbs by hydrogen bonding and hydrophobic interactions, whereas electrostatic interactions dominate at higher surfactant concentrations. Over the entire surfactant concentration range, polymer-surfactant aggregates are present at the edges. The composition of these surface complexes differs from that in solution and is controlled by the surface charge.     

330阴离子交换树脂对草甘膦的吸附性能

采用静态吸附法研究了330阴离子交换树脂对水中草甘膦的吸附性能,并研究了吸附动力学;测定了溶液的pH值、温度、NaCl含量等因素对330树脂吸附草甘膦的影响.结果表明:330树脂对水中草甘膦的吸附速率快;在pH=2.69时对草甘膦的吸附性能最好;330树脂对草甘膦的吸附是放热、自发的过程,吸附等温线符合Freundli...