Rayleigh instability of stationary phase films in capillary column chromatography

The film of stationary phase on the wall of a capillary column and that of the phase solution during both static and dynamic coating is subject to Rayleigh instability, which is quite independent of so-called wettability. A theory is developed which shows that the logarithmic growth rate of Rayleigh instabilities is proportional to the surface tension and to the third power of the film thickness, and inversely to the viscosity and to the fourth power of the capillary diameter. Determination of the variation of the viscosities of stationary phase solutions with concentration in coating solvents, and the variation of the viscosities of neat stationary phases with temperature, both revealed that heating and/or diluting changed the viscosities of phases with π-electron-containing, groups much more than for polydimethylsiloxanes. Rayleigh instability is therefore more important during coating of phenyl-containing phases such as OV-17, and later during column operation. The efficiencies of capillary columns of different diameters coated with a number of phases under different conditions of temperature and coating rate, and then operated at different temperatures were in good agreement with the predictions of the theory.     

Nonionic surfactant enhanced semipermanent coatings for capillary electrophoresis of inorganic anions without use of organic additives

Separation of inorganic anions by capillary electrophoresis (CE) is usually conducted in co-electroosmotic mode due to the large electrophoretic mobilities of inorganic anions. Semipermanent surfactant coatings have been shown to be effective for CE of inorganic anions due to their strong capability of electroosmotic flow (EOF) manipulation. However, semipermanent coatings often suffer from their unsatisfactory stability. In addition, organic solvent additives are usually required to adjust the selectivity, which also aggravate the degradation of coating. In this work, a novel semipermanent coating consisting of cationic Gemini surfactant 18-10-18 and nonionic surfactant Tween 20 was developed to separate inorganic anions in CE. This coating is easy to prepare and more stable than pure Gemini coating. The introduction of nonionic surfactant in the coating not only suppresses the reversed EOF but can also adjust the selectivity of separation. Good separations of six model anions were achieved, the separation efficiency was as high as 65040-169700 plates/m and the RSDs of the migration times were less than 0.5 and 2.5% for run-to-run and day-to-day assays, respectively. Calibration curves were linear in the range of 0.05-5.0 mM; the detection limits ranged from 20 to 50 μM. More importantly, no organic solvents are required in the background buffer to achieve the satisfactory separations. This guarantees the coating stability and makes the method greener than most of other methods for CE of inorganic anions.     

Solution properties of cellulose triacetate. II. Solubility and viscosity studies

The solubility of cellulose triacetate in a range of solvents was measured, and the results for tetrachloroethane, chloroform, and acetic acid were compared with those from initial phase separation in solvent–nonsolvent mixtures and viscosity–concentration studies. The correlation found between solubilities, precipitation values, and values of the Huggins viscosity constant is discussed with reference to the type of polymer–solvent interaction proposed previously to explain fractionation behavior. A qualitative comparison of solubility–swelling behaviour was also made for a very low molecular weight cellulose triacetate sample in a wide range of solvents. Results are compared with those for higher molecular weight samples and discussed with regard to the cohesiveenergy densities of solvent and polymer. Some attempt has been made to predict suitable solvents for cellulose triacetate, based on consideration of their molecular structures.     

LiFeO_2包覆MCFC氧化镍阴极的制备及性能研究

以硝酸锂和硝酸铁为原料 ,柠檬酸作燃料 ,采用燃烧合成法制备了铁酸锂包覆的多孔氧化镍阴极 .X_射线衍射技术 (XRD)、X_射线能量散射谱 (EDAX)和电子显微镜 (TEM和SEM )分析表明 ,在氧化镍颗粒表面的包覆层是由直径小于 10 0nm的铁酸锂微粒所构成 ,并与氧化镍颗粒紧密烧结在一起 ,有效地减少了氧化镍与熔融碳酸盐的接触面积 ,从而降低了氧化镍的溶解度 .同时 ,本文还研究了该阴极在熔融碳酸盐燃料电池中的电性能 ,并与未包覆的NiO阴极进行比较     

Stability of capillaries coated with highly charged polyelectrolyte monolayers and multilayers under various analytical conditions--application to protein analysis

The stability of capillaries coated with highly charged polyelectrolytes under various analytical conditions was studied, as well as their performance for the analysis of proteins by Capillary Electrophoreis (CE) over a wide range of pH (2.5-9.3). In this study, fused silica capillaries were modified either with a poly(diallyldimethylammonium) chloride (PDADMAC) monolayer or PDADMAC/poly(sodium 4-styrenesulfonate) (PSS) multilayer coatings, using optimal coating conditions previously determined. Results show that the coated capillaries are remarkably stable and efficient to limit protein adsorption under a variety of extreme electrophoretic conditions even in the absence of the coating agent in the background electrolyte which is exceptional for non-covalent coatings. Monolayer coated capillaries were demonstrated for the first time to be stable to acidic rinses and to organic solvents which proves that the stability of the capillaries is highly dependent on the coating procedure used. In addition, PDADMAC/PSS multilayer coatings were found to be stable to alkaline treatments. PDADMAC/PSS coated capillaries gave excellent performances for the analysis of proteins covering a large range of pI (4-11) and of molecular weight (14-65 kDa) over a wide pH range (i.e. 2.5-9.3). Even at high pH 9.3, protein analysis was possible with very good repeatabilities (RSD(tm)<1% and RSD(CPA)<2.6% (n ≥ 8)) and high peak efficiencies in the order of 700,000.     

Determination and Correlation of the Solubility of Acetylpyrazine in Pure Solvents and Binary Solvent Mixtures

The solubilities of acetylpyrazine in seven pure solvents and one binary solvent mixture were determined by a dynamic analytic method at temperatures ranging from 268.15 to 308.15 K under atmospheric pressure. For pure solvents, the solubility of acetylpyrazine increases with increasing temperature and solvent polarity. For the binary solvent mixture of ethyl acetate and isopropanol, the solubility increases with increasing temperature and mole fraction of ethyl acetate. The solubility data were correlated with some thermodynamic models, including the modified Apelblat model, λh model, CNIBS/R-K model, and NRTL model. In addition, the relationship between solubility and solvent polarity was investigated by using the Arrhenius equation. All the models or equations gave satisfactory correlation results. The results showed that the solubility of acetylpyrazine generally rises with the increase of solvent polarity at the same temperature. Moreover, the dissolution thermodynamic properties of acetylpyrazine in different solvents were calculated and are discussed based on the NRTL model.     

Some solvent effects on the solvent extraction of 8-quinolinol

The distribution constants of 8-quinolinol between water and a series of substituted aliphatic hydrocarbons, at 25 degrees , are reported. The results are discussed in terms of dielectric constant and solubility parameter of the solvents. For 8-quinolinol, and possibly for its chelates, bromochloromethane, dibromomethane and chloroform seem to be about the best solvents, in that order. Among the solvents studied, chloroform shows significantly higher values than expected; the deviation may be explained as a specific interaction of the hydrogen- bonding type.     

微波辐射加热防爆喷缓冲器的研制与应用

介绍了一种适用于微波化学反应器的防爆喷缓冲装置的结构、工作原理和使用方法。并通过水射流缓冲试验，以及在频率为2450MHz，微波功率为525W下，与常规方法作对比试验。探讨了该装置的防爆喷效果和防溶剂耗散效果，为微波辐射加热减少有害气体的挥发和溶液的爆喷，提供了一种安全的试验装置。     

Thermodynamics of 4’-bromomethyl-2-cyanobiphenyl in different solvents

The melting properties and the heat capacity of the solid state and the melt state 4’-bromomethyl-2-cyanobiphenyl (OTBNBr) were determined. The enthalpy, entropy and Gibbs free energy of fusion were also calculated. The solubility of OTBNBr in eight organic solvents was experimentally measured at temperatures from (283.15 to 323.15) K by using a static method. The reasons for the differences of the solubility of OTBNBr in various solvents are discussed by using the intermolecular interaction. Furthermore, the experimental solubility values were well correlated by the modified Apelblat equation, the λh equation, the Wilson model and the van’t Hoff equation. Finally, the temperature dependence of the activity coefficient and the van’t Hoff enthalpy in the tested solutions was investigated and is discussed.     

Static coating of capillary columns by means of liquefied gases

The technique of spontaneous coating of capillary columns employing liquefied butane and ethylene chloride as solvents of the stationary phase is described. These solvents and their mixtures are suitable for apolar and medium-polar stationary phases. The dependence of coating time on coating temperature and on the composition of the mixture of solvents was observed. It was found that the coating efficiency decreases with increasing coating speed.     

Solubility characteristics of poly(3‐hexylthiophene)

Solubility data for poly(3‐hexylthiophene) (P3HT) in 29 pure solvents are presented and discussed in detail. Functional solubility parameter (FSP) and convex solubility parameter (CSP) computations are performed and the CSP and FSP results are compared to previously reported Hansen solubility parameters (HSPs) and to the parameters calculated using additive functional group contribution methods. The empirical data reveals experimental solubility parameters with substantial polar (δ_P) and hydrogen‐bonding (δ_H) components, which are not intrinsic to the structure of the P3HT polymer. Despite these apparent irregularities, it is shown that the predictor method based on the solubility function, f, does provide a reliable way to quantitatively evaluate the solubility of P3HT in other solvents in terms of a given set of empirical solubility data. The solubility behavior is further investigated using linear solvation energy relationship (LSER) modeling and COSMO‐RS computations of the activity coefficients of P3HT. The LSER model reveals that (1) the cavity term, δ_T, is the dominant factor governing the solubility behavior of P3HT and (2) the solvent characteristics that dictate the structural order (crystallinity) of P3HT aggregates do not similarly influence the overall solubility behavior of the polymer. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1075–1087     

Structure and dynamics of dextran in binary mixtures of a good and a bad solvent

The structure and dynamics of the common polysaccharide dextran have been investigated in mixed solvents at two different temperatures using small-angle X-ray scattering (SAXS) and viscosity measurements. More specifically, binary mixtures of a good solvent (water, formamide, dimethylsulfoxide, ethanolamine) and the bad solvent ethanol as the minority component have been considered. The experimentally observed effects on the polymer conformation (intrinsic viscosity, coil radius, and radius of gyration) of the bad solvent addition are discussed in terms of hydrogen bonding density and are correlated with the Hansen solubility parameters and the surface tension of the solvent mixtures. Hydrogen bonding appears to be an important contributor to the solubility of dextran but is not sufficient to capture the dextran coil contraction in the mixtures of good+bad solvents.     

Spray-Coated Metal Hexadecanoate-Based Coatings with Robust Superhydrophobicity and Repairability

With the aim of creating a new avenue for the real applications of the superhydrophobic surface, we succeeded in fabricating metal hexadecanoate (e.g., zinc hexadecanoate) based superhydrophobic coatings on virtually any substrates by the simple spray-coating. Hierarchical rough surface morphology was achieved on the coating with the contact angle of about 160° and the sliding angle of about 6°. The advantages of the present approach include the cheap raw materials, environmentally benign solvents, an industrial implementation method, and easy repairability and applicability so as to make a great application potential in practice. Water repellency of the fabricated coating was demonstrated by visible experiment results and contact angle measurements. The robustness and repairability of the superhydrophobic coating were also investigated by the designed experiments.     

Simplified analysis of gas/polymer selective solubility behavior

Interactions of penetrants with gas separation membrane materials can have both desirable and undesirable consequences. Improved permselectivity resulting from specific polymer/penetrant interactions must be balanced against potentially undesirable plasticization effects resulting from such interactions. Consideration is given to the utility of gas solubility measurements in low-molecular-weight solvents as an aid to understanding solubility data for polymer/gas systems. The solubility coefficients of gases in low-molecular-weight liquids and in polymeric media of similar chemical structure tend to be quite different in magnitude. “Equation-of-state” and combinatorial entropy differences for the free energy of mixing of gases with low-molecular-weight solvents and high-molecular-weight polymers presumably cause this discrepancy. The above complications are minimized and useful trends identified by considering the so-called solubility selectivity comprised of ratios of absolute gas solubilities in both low-and high-molecular-weight media of similar chemical natures. For example, both acetone and methyl acetate are highly sorptive of CO₂ and display a high degree of solubility selectivity for CO₂ relative to CH₄. These two solvents have mass densities of carbonyl groups that are similar to that in cellulose acetate and poly(methyl methacrylate). Both of these polymers are also highly sorptive of CO₂ and have solubility selectivities for CO₂ relative to CH₄ that are similar to that of acetone and methyl acetate. Anomalous behavior is encountered in the case of Kapton poly(ether diimide), which contains a high density of carbonyl groups (four per repeat unit). On the basis of the behavior of the other carbonyl-rich polymers, it was expected that Kapton would show high solubility selectivity for CO₂ relative to CH₄, but this was not observed. A hypothetical explanation for the Kapton behavior is presented. In addition, possible advantages of the Kapton-type behavior are discussed in the context of the reported good plasticization resistance of polyimides.     

Solvent versatility of immobilized 3,5-dimethylphenylcarbamate of amylose in enantiomeric separations by HPLC

CHIRALPAK IA is a new chiral stationary phase containing amylose 3.5-dimethylphenylcarbamate immobilized onto silica gel. It is compatible with the whole range of organic solvents. Its solvent versatility has been thoroughly investigated. The option to use a wide range of solvents, especially the "non-standards" ones, in the mobile phase enables the enhancement of chiral separation methods in terms of enantioselectivity, resolution, analysis time, sample injection and sample solubility. Parameters such as the mobile phase type, the nature of modifier and eluting strength of various solvents are examined and discussed. A guideline for method development and optimization on CHIRALPAK IA is also proposed.     

An evaluation of thermodynamic models for the prediction of drug and drug-like molecule solubility in organic solvents

Prediction of solubility of active pharmaceutical ingredients (API) in different solvents is one of the main issue for crystallization process design. Experimental determination is not always possible because of the small amount of product available in the early stages of a drug development. Thus, one interesting perspective is the use of thermodynamic models, which are usually employed for predicting the activity coefficients in case of Vapour-Liquid equilibria or Liquid-Liquid equilibria (VLE or LLE). The choice of the best thermodynamic model for Solid-Liquid equilibria (SLE) is not an easy task as most of them are not meant particularly for this. In this paper, several models are tested for the solubility prediction of five drugs or drug-like molecules: Ibuprofen, Acetaminophen, Benzoic acid, Salicylic acid and 4-aminobenzoic acid, and another molecule, anthracene, a rather simple molecule. The performance of predictive (UNIFAC, UNIFAC mod., COSMO-SAC) and semi-predictive (NRTL-SAC) models are compared and discussed according to the functional groups of the molecules and the selected solvents. Moreover, the model errors caused by solid state property uncertainties are taken into account. These errors are indeed not negligible when accurate quantitative predictions want to be performed. It was found that UNIFAC models give the best results and could be an useful method for rapid solubility estimations of an API in various solvents. This model achieves the order of magnitude of the experimental solubility and can predict in which solvents the drug will be very soluble, soluble or not soluble. In addition, predictions obtained with NRTL-SAC model are also in good agreement with the experiments, but in that case the relevance of the results is strongly dependent on the model parameters regressed from solubility data in single and mixed solvents. However, this is a very interesting model for quick estimations like UNIFAC models. Finally, COSMO-SAC needs more developments to increase its accuracy especially when hydrogen bonding is involved. In that case, the predicted solubility is always overestimated from two to three orders of magnitude. Considering the use of the most accurate equilibrium equation involving the ΔC_p term, no benefits were found for drug predictions as the models are still too inaccurate. However, in function of the molecules and their solid thermodynamic properties, the ΔC_p term can be neglected and will not have a great impact on the results.     

The determination of the solubility of organic solvents in mineral acids

A knowledge of the solubility of organic solvents in aqueous solutions of mineral acids is shown to be important in solvent extraction studies. The method described depends upon the direct measurement of the amount of solvent thrown out of the aqueous phase on neutralization. The results of experiments on the solubility of iso-propyl ether in aqueous hydrochloric acid are given. The accuracy, limitations, and uses of the method are discussed.     

Overcoming the insolubility of carbon nanotubes through high degrees of sidewall functionalization

The use of carbon nanotubes in materials applications has been slowed due to nanotube insolubility and their incompatibility with polymers. We recently developed two protocols to overcome the insoluble nature of carbon nanotubes by affixing large amounts of addends to the nanotube sidewalls. Both processes involve reactions with aryl diazonium species. First, solvent-free functionalization techniques remove the need for any solvent during the functionalization step. This delivers functionalized carbon nanotubes with increased solubility in organic solvents and processibility in polymeric blends. Additionally, the solvent-free functionalization process can be done on large scales, thereby paving the way for use in bulk applications such as in structural materials development. The second methodology involves the functionalization of carbon nanotubes that are first dispersed as individual tubes in surfactants within aqueous media. The functionalization then ensues to afford heavily functionalized nanotubes that do not re-rope. They remain as individuals in organic solvents giving enormous increases in solubility. This protocol yields the highest degree of functionalization we have obtained thus far-up to one in nine carbon atoms on the nanotube has an organic addend. The proper characterization and solubility determinations on nanotubes are critical; therefore, this topic is discussed in detail.     

SiO2/α-FeOOH和SiO2/γ-Fe2O3微粒的界面研究

α－FeOOH微粒由于其表面高活性，在转变成γ－Fe2O3的热处理过程中容易烧结，一旦这种烧结现象发生，得到的γ－Fe2O3磁粉磁性能大大下降[1]．为了克服这一困难，目前采用在α-FeOOH微粒表面包敷有机物[2]和无机物[3]来隔离颗粒，阻止其聚集．其中SiO2表面包敷处理是最令人感兴趣的研究课题之一[4，5]．SiO2是一种难烙性的非磁性材料，它包敷在α-FeOOH微粒表面外，不仅可提高α－FeOOH转变成γ－Fe2O3的热处理温度，有利于得到外形完好、晶格完整的γ－Fe2O3磁粉，而且由包效层与内核之间的界面相互作用引起的表面各向异性常…     

Synthesis and spectroscopic properties of highly water-soluble perylene derivatives

Most known perylene diimides are lipophilic, with few exceptions of hydrophilic derivatives. Even in the latter case, the compounds have limited water solubility and show a strong tendency to self-aggregation. In this paper we present the synthesis of four new perylene derivatives with three and four basic side chains, obtained by functionalizing the bay-area of perylene. These molecules show great solubility in aqueous media as hydrochlorides and their tendency to self-aggregate is remarkably reduced with respect to the previously synthesized two-chained perylene diimides. Their different spectroscopic properties in various solvents and conditions are reported and discussed.