Nonionic Species Research Articles

Analysis of Cationic Structure in Some Room-Temperature Molten Fluorides and Dependence of Their Ionic Conductivity and Viscosity on Hydrofluoric Acid Concentration

To understand the ionic and nonionic species in (CH(3))(4)NF·mHF, (CH(3))(3)N·mHF, (C(2)H(5))(4)NF·mHF, and (C(2)H(5))(3)N·mHF melts, the structures of these melts were investigated by infrared spectroscopy, NMR, and high-energy X-ray diffraction. Infrared spectra revealed that three kinds of fluorohydrogenate anions, (FH)(n)F(-) (n = 1, 2, and 3), and molecular hydrofluoric acid (HF) are present in every melt. Ionic conductivity and viscosity of these melts were measured and correlated with their cationic structure. The ionic conductivity of the R(4)N(+)-systems was higher than that of corresponding R(3)NH(+)-systems because a strong N-H···F(HF)(n) interaction prevents the motion of R(3)NH(+) cations in the R(3)N·mHF melts. (CH(3))(4)N(+) and (CH(3))(3)NH(+) cations gave higher ionic conductivity than (C(2)H(5))(4)N(+) and (C(2)H(5))(3)NH(+) cations, respectively, because the ionic radii of former cations were smaller than those of latter. It was concluded that these effects on ionic conductivity can be explained by the cationic structure and the concentration of molecular HF in the melts.

Pharmaceutical suspensions: micro electrophoretic properties.

The microelectrophoretic properties of the drugs griseofulvin, betamethasone, nalidixic acid and thiabendazole in aqueous dispersion have been examined and the zeta potentials calculated from the measured mobilities. Variation in magnitude of particle charge with pH of dispersion is reported and related to the chemical structure and the surface characteristics. The effect of adding anionic (sodium dodecyl sulphate) cationic (dodecyl trimethyl bromide) and non-ionic (polyoxyethylene glycol monoethers of hexadecanol) surface-active agents, and mixtures of these ionic and non-ionic species, on the electrophoretic properties of the drug dispersions has been measured. The results reported agree with those found previously for a model polystyrene latex suspension system under the same conditions.

Modeling of electrokinetic processes by finite element integration of the Nernst–Planck–Poisson system of equations

Electrokinetic remediation covers a variety of useful techniques for the mobilization of ionic and non-ionic species from porous materials by means of the application of an external electric field. Due to the large number of physicochemical interactions in the process, designing an electrokinetic remediation process is not simple. Mathematical models are necessary for a better understanding of its fundamentals. In this study, a model for the electrokinetic transport phenomena based on the strongly coupled Nernst–Planck–Poisson system of equations is described. In the model presented here, the diffusion, the electromigration and the electroosmotic transport contributors are taken into account. The Poisson's equation of electrostatics is used for the calculation of the electrical potential distribution based on the global charge balance. The effect of the electrode half-reactions is included. In addition to this, water equilibrium is continuously assured and the pH value is monitored. Results from some selected test simulations of the electrokinetic desalination of a sample of porous material are presented, outlining the versatility of the model as well as showing the effect of the counterion in the removal rate of a target ion.

Encaging the Verkade’s Superbases: Thermodynamic and Kinetic Consequences

Proazaphosphatranes, also known as Verkade's superbases, are nonionic species, which exhibit catalytic properties for a wide range of reactions. The properly designed host molecule 3 and its protonated counterpart [3·H](+)Cl(-) were synthesized to study how confinement can modify the stability and the reactivity of a Verkade's superbase. The results show that the encapsulation does not alter the strong basicity of the proazaphosphatrane, but dramatically decreases the rate of proton transfer.

Analysis of Cationic Structure in Some Room Temperature Molten Fluorides and Dependence of Their Ionic Conductivity and Viscosity on HF-Concentration

To understand the ionic and non-ionic species in (CH3)4NF⋅mHF, (CH3)3N⋅mHF, (C2H5)4NF⋅mHF, and (C2H5)3N⋅mHF melts, the structures of these melts were investigated by infrared spectroscopy, NMR and high-energy X-ray diffraction. IR spectra revealed that the complex fluoride anions such as (HF)nF- (n = 1, 2, 3) and molecular HF are present in all melts. Ionic conductivity and viscosity of these melts were measured and correlated with their cationic structure. The ionic conductivity of the R4N+-systems was higher than those of corresponding R3NH+-systems. (CH3)4N+ and (CH3)3NH+ cation gave higher ionic conductivity than (C2H5)4N+ and (C2H5)3NH+ cation, respectively. It was concluded that these effects on ionic conductivity can be explained by the cationic structure and the concentration of molecular HF in the melts.

HPLC-SPE-NMR in studies of medicinal plants and herbal products

Hyphenated NMR spectroscopy is a state-of-the-art method for rapid and rigorous determination of natural product structures in plant extracts without isolation of the individual components in the classical sense. Among hyphenated NMR techniques, HPLC-SPE-NMR is the most convenient and superior in terms of quality of data, the most serious limitation being problems with solid-phase extraction of highly polar but nonionic species. The technique is particularly important in projects aimed at discovery of new chemical entities in medicinal plants, e.g., in connection with natural product discovery of novel pharmacologically active compounds. Moreover, studies related to standardization and uniformity of herbal products, performed either using metabolomic techniques or traditional methods, can benefit from support by hyphenated NMR experiments. HPLC-SPE-NMR work can be performed either using a flow NMR probe or a microtubes, and will benefit from increased sensitivity of cryogenically cooled probes. Examples of use of HPLC-SPE-NMR in analysis of medicinal plants and herbal products will be shown.

Adsorption and recovery of nonionic polymers by neutralization of cellulose fiber surface charge via cationic polyamide‐epichlorohydrin resins

AbstractNonionic copolymers, such as poly(1‐vinylpyrrolidone)‐polystyrene, have been used in the production of filtration membranes, catalysts, and sensors. However, their nonionic character and high solubility in water prevents their efficient recovery from waste streams. Cellulose fibers show potential as recovery agents because they are inexpensive, environmentally friendly, and have a large surface area per unit mass. However, due to the anionic nature of the cellulose fiber surface, their adsorptive behavior is often limited to cationic species. We have shown that low‐dosage application of a cationic polyamide‐epichlorohydrin resin can alter the fiber surface charge so as to provide more neutral surface area for the nonionic polymer to adsorb; furthermore, the adsorbed polyamide‐epichlorohydrin resin does not block the approach of poly(1‐vinylpyrrolidone)‐polystyrene. Single‐component adsorption of poly(1‐vinylpyrrolidone)‐polystyrene was on the order of 10−3 g/g; with polyamide‐epichlorohydrin resin adsorbed on the fiber, the adsorption increased one‐order of magnitude to 10−2 g/g. We believe this significant increase is caused by neutralization of fiber surface charge via polyamide‐epichlorohydrin resin, creating a surface more favorable for adsorption and recovery of nonionic species. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Metal oxides immobilized fabrics by radiation induced graft polymerization

Radiation induced graft polymerization is effective for adding a new functionality to various forms of existing polymers. Ion-exchange nonwoven fabrics by gamma radiation induced graft polymerization have been used as filters in air and liquid. However, these materials have no capability for removing non-ionic species, such as volatile organic compound and ozone. Manganese oxides immobilized fabrics were developed for removing ozone. In addition, these materials were capable of removing formaldehyde and arsenic. Fine particles of manganese oxides were observed on the fibers. New materials produced by radiation induced graft polymerization and metal immobilization were applicable for purification of contaminants in environment. Manufacturing process is applicable for immobilization of the other metal oxides.

Synthesis and Characterization of Some Amino Acid Derived Schiff Bases Bearing Nonionic Species as Corrosion Inhibitors for Carbon Steel in 2N HCl

A novel series of nonionic amino acid Schiff-Bases were synthesized and characterized using different spectroscopic tools to elucidate their chemical structures. The surface and thermodynamic properties of these compounds were studied using classical measurements including surface and interfacial tension and emulsification tendency. The surface parameters of these compounds including surface tension, critical micelle concentration (CMC), effectiveness (πcmc), efficiency (Pc20), maximum surface excess (Γmax), and minimum surface area (Amin) showed their good surface activity. Their thermodynamic parameters of adsorption and micellization including free energy change of micellization and adsorption showed their tendency toward adsorption at the interfaces and also micelle formation at lower concentrations. The synthesized compounds were also evaluated as corrosion inhibitors for carbon steel at different doses (400, 200, 100, 50, and 25 ppm) in 2 N HCl using gravimetric technique (weight loss). The results showed that these inhibitors are characterized by very high corrosion inhibition efficiency ranged between 99.93% and 97.98% and low corrosion rates varied between 0.09 mpy and 0.17 mpy for higher doses (400 ppm). The efficiency of inhibition was decreased by increasing the exposure time. The most efficient corrosion inhibitor of the synthesized compounds was the inhibitor which contains polyethylene oxide chain length of 23 EO units and alkyl chain length of 12 methylene groups. The effect of the hydrophobic and hydrophilic chain length in the inhibitor molecules was discussed and rationalized with their inhibition efficiency. The tendency of these inhibitors toward complexation with the transition metals was also discussed in order to explain their higher efficiency.

Local structure and composition of the ionic aggregates in Cu(II)-neutralized poly(styrene-co-methacrylic acid) ionomers depend on acid content and neutralization level

The morphologies of poly(styrene-ran-methacrylic acid) (SMAA) copolymers neutralized with Cu(II), including the local structure and composition of the ionic aggregates, were investigated as a function of acid content and level of neutralization. X-ray scattering and scanning transmission electron microscopy (STEM) results suggested that the sizes of the ionic aggregates in Cu(II)-neutralized SMAA are independent of the acid content and neutralization level. The number density of ionic aggregates increased slightly with acid content and neutralization level, but the increase was significantly less than expected for aggregates of fixed composition. Electron spin resonance (ESR) spectra of Cu(II) detected three distinct cation sites whose relative amounts changed with acid content. These results combined to indicate that the ionic aggregates contain non-ionic species and that the aggregate compositions become more ionic with increasing acid content and neutralization level.

Protonation Behavior and Stability of Micelles of N-Lauroylaminoalkyl-Dimethylamine Oxides-Effects of Added Salt Concentration and Spacer Length

The protonation behavior and the stability of micelles of N-lauroylaminopropyl-N',N'- dimethylamine oxide (C12AmCn; n=3) were studied by the hydrogen ion titration and the equilibrium surface tension measurement. The surface potential of C12AmC3 micelles estimated from the results of hydrogen ion titration was lower than that of dodecyldimethylamine oxide micelles at added NaCl concentration, C(S), of 0.1M. The critical micelle concentration (cmc) estimated from surface tension measurements revealed that a reversal of the stability of the cationic and the nonionic micelles of C12AmC3 takes place in the range of C(S) higher than about 0.2M, that is, the cationic micelles become more stable than the nonionic ones in the range C(S) >or= 0.2M. In addition, the surface tension measurements were carried out for C12AmCn with different spacer length, n, ranging from 2 to 6 methylene units at C(S) = 0.1M. The cmc values of nonionic species were kept at almost constant for n <or= 4, while they decreased with n for n >or= 4. The cmc values of cationic species also tended to decrease with n for n >or= 4. These results were compared with those obtained for alkyldimethylamine oxides, and the effect of amide group and spacer groups introduced into amine oxide surfactants was discussed.

Monitoring of enzymatic reactions using conventional and on‐chip capillary electrophoresis with contactless conductivity detection

The use of CE with contactless conductivity detection was evaluated for monitoring enzymatic reactions. The nonionic species ethanol, glucose, ethyl acetate, and ethyl butyrate were made accessible for analysis by CE via charged products or by-products obtained in enzymatic conversions using hexokinase, glucose oxidase, alcohol dehydrogenase, and esterase. Two of the reactions, namely the conversion of glucose with glucose oxidase and that of ethylacetate with esterase, were also successfully demonstrated on a microchip device. Quantification for ethyl acetate, taken as an example, was found possible with a detection limit of approximately 7 microM.

The role of cationic Au 3+ and nonionic Au 0 species in the low-temperature water–gas shift reaction on Au/CeO 2 catalysts

The roles of cationic and nonionic Au species in the water–gas shift (WGS) reaction on Au/CeO 2 catalysts were studied by comparing the reaction behavior of a cyanide leached catalyst, after removal of the Au nanoparticles by cyanide leaching, with that of non-leached catalysts, following the technique introduced by Q. Fu et al. [Science 301 (2003) 935]. Using rate measurements as well as in situ spectroscopic and structure-sensitive techniques, we found that based on the Au mass balance, cyanide leaching removed all Au except for ionic Au 3+ species, and that leaching resulted in a pronounced decay of the catalyst mass normalized activity to 1–25% of that of a non-leached catalyst. The extent of the activity loss strongly depended on the post-treatment of the leached catalyst. Both the catalyst treatment after leaching and, in particular, the WGS reaction resulted in considerable reformation of Au 0 species by thermal decomposition of Au oxides (Au 3+) and subsequent nucleation and growth of very small Au 0 aggregates and metallic Au 0 nanoparticles, as indicated by Au(4f) signals at 85.9 eV (Au 3+), 84.0–84.6 eV (up-shifted signal of small Au 0 aggregates), and 84.0 eV (metallic Au 0). In this work, correlations between ionic and nonionic Au species and between total WGS activity and activity for the formation/decomposition of bidentate formate species are evaluated, and the role of the respective Au species in the WGS reaction on Au/CeO 2 catalysts is discussed.

Stearic Acid Spin Labels in Lipid Bilayers: Insight through Atomistic Simulations

Spin-labeled stearic acid species are commonly used for electron paramagnetic resonance (EPR) studies of cell membranes to investigate phase transitions, fluidity, and other physical properties. In this paper, we use large-scale molecular dynamics simulations to investigate the position and behavior of nitroxide spin labels attached to stearic acid molecules in dipalmitoylphosphatidylcholine (DPPC) bilayers. The results of these studies are potentially very important for the interpretation of EPR spectra, which rely on assumptions about the position of the label in the membrane. Additionally, we investigate the effect of chirality and ionization of the carboxyl group of the label. For a non-ionized species, we observe that spin-label molecules are even able to make flip-flop transitions between the leaflets of the bilayer. Such transitions have been previously observed only in very rare cases in molecular simulations.

The effects of pH on fluoxetine in Japanese medaka ( Oryzias latipes): Acute toxicity in fish larvae and bioaccumulation in juvenile fish

Recent detection of fluoxetine in the aquatic environment and fish suggests a possibly high accumulation of fluoxetine; however, no report is available on the bioaccumulation of fluoxetine in aquatic organisms. Since bioaccumulation of fluoxetine was probably dependent on pH near the p K a value of 10.1, experiments were conducted approximately at pH 7, 8, and 9. Distribution coefficients between 1-octanol and water ( D ow), and those between synthetic membrane vesicles (liposomes) and water ( D lip–wat) were determined at pH 7, 8, and 9. The D ow and D lip–wat values increased significantly with increasing pH. Acute toxicity tests were performed using Japanese medaka ( Oryzias latipes) prior to the bioaccumulation test, and 96-h LC 50 values were 5.5, 1.3, and 0.20 mg l −1 at pH 7, 8, and 9, respectively. In the bioaccumulation test, concentrations of fluoxetine and its major metabolite, norfluoxetine, in the fish body and liver were measured. The bioconcentration factors (BCF) of fluoxetine for Japanese medaka were 8.8, 3.0 × 10, and 2.6 × 10 2 in the body and 3.3 × 10 2, 5.8 × 10 2, and 3.1 × 10 3 in the liver at pH 7, 8, and 9, respectively. The BCF values were lower at pH 7 and higher at pH 9 mainly because of the increase in nonionized species with significantly higher hydrophobicity than the ionized species at pH values closer to p K a. A similar trend was obtained for the concentration of norfluoxetine in the fish but the pseudo-BCF values (the ratio of the norfluoxetine concentration in the fish and the fluoxetine concentration in test water) were higher than the BCF value of fluoxetine at all pH conditions.

Quantitative Morphology Study of Cu-Neutralized Poly(styrene-ran-methacrylic acid) Ionomers: STEM Imaging, X-ray Scattering, and Real-Space Structural Modeling

Our previous study showed quantitative correspondence between the size of ionic aggregates in a Cu-neutralized poly(styrene-ran-methacrylic acid) ionomer (Cu-SMAA) measured from scanning transmission electron microscopy (STEM) images and the sizes determined from X-ray scattering data interpreted using the Yarusso−Cooper model. Here we compare the average sample volume per ionic aggregate (Vp) from STEM images and X-ray scattering data from Cu-SMAA. The relationship between the 3D morphology of hard spheres as defined by the Yarusso−Cooper parameters (R1, RCA, Vp) and the projected 2D images obtained by STEM was elucidated by modeling. These simulations show that a significant number of the ionic aggregates in Cu-SMAA are obscured due to overlap effects and provide a quantitative relationship between the number of spheres in 3D and the number of features in 2D projections as a function of specimen thickness. Upon measuring the local thickness of a Cu-SMAA specimen using electron energy loss spectrometry (EELS), we find that the Vp determined from STEM images strongly agrees with that determined from X-ray scattering data. Thus, quantitative correspondence of both the size and number density of ionic aggregates has been obtained from direct imaging and X-ray scattering of Cu-SMAA. These data provide compelling evidence that the Yarusso−Cooper scattering model presents an excellent description of the nanoscale morphology of this solvent cast ionomer. Interpretation of this morphological data indicates that the ionic aggregates likely include both ionic and nonionic species. This comprehensive characterization provides a foundation on which a systematic evaluation of the factors that influence the nanoscale morphology, and consequently the macroscopic properties, can be accomplished.

Solvent Effect on the Electronic Spectra of Azine Dyes under Alkaline Condition

Thiazine dye, methylene blue (MB), oxazine dye, nile blue (NB), and phenazine-based dye, neutral red (NR), bear a similar basic dye skeleton with a distinctively different central heteroatom. All of them are extracted into nonpolar organic solvent from alkaline solution. The role of the heteroatom on the respective dye skeletons and redox potentials of the dyes has been examined to signature the stability of the species in organic solvent and the results have been substantiated through geometry optimization and wave function analysis at the density functional theory level. The effect of solvent polarity on the electronic absorption spectra of the three nonionic benzenoid species has been investigated with an intention to investigate the solvatochromic behavior of these compounds.

Application of Chromatographic and Electrophoretic Methods for the Analysis of Imidazolium and Pyridinium Cations as Used in Ionic Liquids

Interest in ionic liquids for their potential in different chemical processes isconstantly increasing, as they are claimed to be environmentally benign – excellent, non-volatile solvents for a wide range of applications. The wide applicability of thesecompounds also demands reliable, relatively simple and reproducible analytical techniques.These methods must be applicable not only to different technical or natural matrices but alsoto the very low concentrations that are likely to be present in biological and environmentalsystems. In this review, therefore, methods for separating and analysing imidazolium- andpyridinium-type ionic liquids in aqueous matrices using high performance liquidchromatography (HPLC) and capillary electrophoresis (CE) are examined. The techniquesfor identifying ionic liquids are meant primarily to track the concentrations of ionic liquidsas residues not only in products and wastes but also in biological or environmental samples.The application of hyphenated techniques in this field is intended to selectively separate thequaternary entity from other cationic and non-ionic species present in the matrix, and toenable its fine-scale quantification. Nowadays, methods developed for cation analysis arebased mostly on reversed-phase high-performance liquid chromatography, ionchromatography, ion-pair chromatography and capillary electrophoresis, where variousbuffered mobile phases are used.

A dibasic acid with reversed order of the stepwise ionization constants: 2,7‐dichlorofluorescein in the ternary solvent mixture benzene–ethanol–water

AbstractThe ionization constants of 2,7‐dichlorofluorescein were determined and the molecular structures of the equilibrium forms were established in the ternary solvent system benzene–ethanol–water (mass ratio 47:47:6) by using visible spectroscopy. In this solvent mixture with relative dielectric constant εr = 12.8 and normalized Reichardt's parameter E = 0.587, an inversion of the stepwise ionization constants of the dye, Ka1 and Ka2, occurs. The Ka1/Ka2 ratio changes from 16 in water and 4.8 in 50 mass % aqueous ethanol to 0.1 in the ternary solvent system with ionic strength of 0.002 mol dm−3, where pKa1 = 9.23 ± 0.08 and pKa2 = 8.22 ± 0.08 (25 °C). Such an extraordinary interrelation between the Ka constants is in line with the molecular structure of ionic and nonionic species of 2,7‐dichlorofluorescein deduced from their vis absorption spectra, as well as with the expressed salt effects and the probable ion association. The dianion R2− (5 in Scheme 1) possesses a band with λmax = 512 nm and a molar absorptivity of E = 84.3 × 103 cm−1 mol−1 dm3. The tautomeric equilibrium of the neutral form, H2R, is strongly shifted toward the colorless lactone (2 in Scheme 1). The (very intensive) absorption band of the HR− species singled out from the vis spectra at different acidity, is red‐shifted by Δλ ≈ 20 nm against the band of the dianion R2−. Hence, the monoanion HR− is found to be completely converted into the ‘phenolate’ tautomer 4 with groups COOH and O−, while in aqueous solutions the ‘carboxylate’ tautomer 3 with groups COO− and OH predominates. In 50 mass % aqueous ethanol, the two tautomers 3 and 4 exist in commensurable concentrations. Emission and fluorescence excitation spectra and fluorescence quantum yield of the dianion R2− in the ternary solvent mixture were determined. Copyright © 2006 John Wiley &amp; Sons, Ltd.

One-dimensional assemblies of platinum nanoparticles on a graphite surface using nonionic/ionized mixed hemicylindrical micelle templates

One-dimensional (1-D) self-assemblies of Pt nanoparticles on a graphite surface have been synthesized via a template-directed sintering process of individual nanoparticles, using nonionic/cationic mixed hemicylindrical micelle templates of dodecyldimethylamine oxide surfactant at graphite/solution interfaces. The dimension and morphology of Pt nanoparticles can be widely controlled by the concentration of Pt ions equivalent to the mixing ratio of nonionic and cationic species in the surfactant micelle. This approach could be extended to fabricate a wide range of self-assembling metallic nanostructures on surfaces using various nonionic/cationic mixed micelle-like self-assemblies carrying metal ions at interfaces, while providing a fundamental insight into a 1-D self-assembly from individual nanoparticles.