Inorganic Counterions Research Articles

Influence of inorganic counterion on thermodynamic quantities of micellar solubilization of chiral pharmaceutical compounds in aqueous solutions ofN-dodecoxycarbonylvaline using micellar electrokinetic chromatography

Using the van't Hoff relationship, the enthalpy and entropy of transfer of 12 pairs of enantiomeric pharmaceutical compounds, including β-agonists, β-blockers, and other β-amino alcohols, were measured from the aqueous phase to three different counterion (Li+, Na+, and K+) chiral micellar phases. Selectivities, distribution coefficients, and Gibbs free energies were also determined. Whereas the transfer of solute from the aqueous phase to the chiral micellar phase was nearly always favorable from an enthalpic viewpoint (−23<ΔH°<1 kJ/mol), it was not always so from an entropic perspective (−25<ΔS°<57 J/mol K). Dramatic differences in ΔH° and ΔS° were often observed between enantiomers. The lithium counterion system gave the most favorable entropic contribution (positive ΔS) to the free energy of solute transfer, while the potassium counterion system gave the most favorable enthalpic contribution (negative ΔH°). The enthalpy and entropy changes for the solutes follow a linear free-energy relationship for all counterion systems, indicating a similar enantiomeric mechanism of separation. Experimentally determined thermodynamic parameters were related to changes in the polarity of the N-dodecoxycarbonylvaline micelles as a function of counterion to better understand the interactions of enantiomers with these micelles. In contrast to the large changes in ΔH° and ΔS° observed for individual solutes as the counterion was changed, ΔG° and enantioselectivity remained similar. © 1998 John Wiley & Sons, Inc. J Micro Sep 10: 633–645, 1998

Influence of inorganic counterion on thermodynamic quantities of micellar solubilization of chiral pharmaceutical compounds in aqueous solutions of N‐dodecoxycarbonylvaline using micellar electrokinetic chromatography

Influence of inorganic counterion on thermodynamic quantities of micellar solubilization of chiral pharmaceutical compounds in aqueous solutions of N‐dodecoxycarbonylvaline using micellar electrokinetic chromatography

Stability study of conducting polypyrrole films and polyvinylchloride-polypyrrole composites doped with different counterions

Electrically conducting poiypyrrole and poiyvinylchloride-polypyrrole (PVC-PPY) composite films doped with different counterions were aged in ambient air at room temperature. Polypyrrole and PVC-PPY composite films doped with the organic counterion TsO − (paratoluenesulfonate) show better stability than those doped with inorganic counterions as ClO 4 −, BF 4 −, NO 3 −. We found that the normalized conductivity for air ageing at room temperature for 110 days is between 25 and 30% initial conductivity for pure polypyrrole films doped with C1O 4 − and 10% for BF 4 −-doped polypyrrole. For PVC-PPY composites doped with ClO 4 − the normalized conductivity for air ageing at room temperature is between 15 and 35% initial conductivity. For pure polypyrrole and PVC-PPY composites films doped with TsO −, the normalized conductivity for air ageing for 55 days is between 97 and 128% initial conductivity. It was observed that the conductivity of pure polypyrrole and PVC-PPY composite films doped with inorganic ions decreased drastically in the first days, while that of the films doped with organic ion (TsO −) increased. This different behaviour is attributed to the nature of the doping ions.

Effect of Counterions on Ordered Phase Formation in Suspensions of Charged Rodlike Cellulose Crystallites

Stable colloidal suspensions of cellulose crystallites with negatively charged sulfate groups on their surface were prepared by acid hydrolysis of filter paper. The suspensions, which were free of added electrolyte, formed chiral nematic ordered phases above a critical concentration. A sharp boundary was observed between coexisting chiral nematic and isotropic phases, enabling measurements to be made of the relative amounts of each phase as a function of total cellulose concentration. The isotropic-to-chiral nematic phase equilibrium was sensitive to the nature of the counterions present in the suspension. Samples were prepared with sodium, potassium, cesium, ammonium, tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, trimethylammonium, and triethylammonium counterions. Suspensions with H+ counterions formed an ordered phase at the lowest concentrations of crystallites. For inorganic counterions, the critical concentration for ordered phase formation increases in the order ...

Anion Controlled Donor Alignment: Electrosynthesis and Crystal Structure of a Novel Cation Radical Salt Constructed from Porphyrin and Hexatungstate

Abstract Elecrtochemical oxidation of tetrabutanoporphyrin free base with hexatungustate electrolyte produces a novel cation radical salt. X-ray crystallographic study showed that the crystal structure is constructed by C–H···O hydrogen bonds between the porphyrin and the inorganic counter anion.

Competition between Monovalent and Divalent Counterions in Surfactant Systems

Competition between mono- and divalent ions in the association of counterions to the headgroups of amphiphiles was studied in one surfactant system with organic counterions (piperidine+/piperazine2+octanesulfonate) and one with inorganic counterions (Na+/Ca2+octyl sulfate). By conductivity and13C NMR chemical shift measurements the critical micelle concentration (CMC) was found to decrease drastically when small amounts of divalent counterions were present in the system. Self-diffusion coefficients of surfactant ions and organic counterions were measured in the micellar phase by the Fourier transform pulsed-gradient spin-echo (FT-PGSE) NMR method. The degree of counterion binding in the micellar system with piperidine+/piperazine2+counterions was obtained from FT-PGSE NMR measurements. It was observed that the divalent counterions were more strongly bound than the monovalent counterions. The experimental results were compared with theoretical Poisson–Boltzmann calculations. The cell model was used to study the electrostatic effects. Good agreement between electrostatic theory and experiment was observed; however, an attractive force exists between the monovalent piperidine counterions and the micelle, probably because of hydrophobic interactions.

Identification of glutamic acid 113 as the Schiff base proton acceptor in the metarhodopsin II photointermediate of rhodopsin.

In order to investigate the molecular mechanism of rhodopsin photoactivation, site-directed mutants of bovine rhodopsin were studied by Fourier-transform infrared (FTIR) difference spectroscopy. Rhodopsin mutants E113D and E113A were prepared in which the retinylidene Schiff base counterion, Glu113, was replaced by Asp and Ala, respectively. FTIR difference spectra were recorded and compared with spectra of recombinant native rhodopsin. Both mutant pigments formed photoproducts at 0 degrees C with vibrational absorption bands typical of the metarhodopsin II (MII) state of rhodopsin. The FTIR difference spectrum of E113D was nearly identical to that of rhodopsin. A positive band at 1712 cm-1 caused by the protonation of an internal carboxylic acid in rhodopsin was shifted slightly to 1709 cm-1 in mutant E113D. E113A was studied at acidic pH in the presence of chloride as an inorganic counterion to the protonated Schiff base. The 1712-cm-1 (1709-cm-1) band was absent in the FTIR difference spectrum of mutant E113A. Therefore, we have assigned the 1712-cm-1 absorbance band to the C = O stretching vibration of protonated Glu113 in MII of rhodopsin. These results show that the Schiff base counterion of rhodopsin, the carboxylate side chain of Glu113, becomes protonated during MII formation.

Generalized synthesis of periodic surfactant/inorganic composite materials

THE recent synthesis of silica-based mesoporous materials1,2 by the cooperative assembly of periodic inorganic and surfactant-based structures has attracted great interest because it extends the range of molecular-sieve materials into the very-large-pore regime. If the synthetic approach can be generalized to transition-metal oxide mesostructures, the resulting nanocomposite materials might find applications in electrochromic or solid-electrolyte devices3,4, as high-surface-area redox catalysts5 and as substrates for biochemical separations. We have proposed recently6 that the matching of charge density at the surfactant/inorganic interfaces governs the assembly process; such co-organization of organic and inorganic phases is thought to be a key aspect of biomineralization7. Here we report a generalized approach to the synthesis of periodic mesophases of metal oxides and cationic or anionic surfactants under a range of pH conditions. We suggest that the assembly process is controlled by electrostatic complementarity between the inorganic ions in solution, the charged surfactant head groups and—when these charges both have the same sign—inorganic counterions. We identify a number of different general strategies for obtaining a variety of ordered composite materials.

Structural investigations of two 2‐amino‐5‐nitropyridinium Salts: C5H6N3ONO and (C5H6N3O)2CuCl

AbstractThrough chemical preparations and crystal structures of the 2‐amino‐5‐nitropyridinium nitrate and the bis(2‐amino‐5‐nitropyridinium)tetrachlorocuprate, an attempt at polar crystal engineering using the 2‐amino‐5‐nitropyridinium cation and inorganic counter anions is illustrated. The role of the ratio of anion charge to dimension in the building of centric packings is illustrated and discussed. In the tetrachlorocuprate salt, distorted CuCl tetrahedral anions of D2d symmetry are present. C5H6N3ONO is monoclinic, P21/n, with a = 13.672(3), b = 7.762(1), c = 7.577(1) Å, β = 101.45(5)°, Z = 4, dx = 1.703. The crystal structure has been solved using 1 386 independent reflections with a final R value of 0.044. (C5H6N3O)2CuCl is monoclinic, P21/c, with a = 7.701(3), b = 31.99(5), c = 7.107(3) Å, β = 92.65(5)°, Z = 4, dx = 1.844. The crystal structure has been solved using 3 367 independent reflections with a reliability factor of 0.039.

Magnetic interactions between electron spins on organic molecules and halogenometalate ions in TTF- and BEDT-TTF-MX4 complexes (M = Mn, Co, Cu)

The cation radical salts of TTF and BEDT-TTF with tetrahalogenometalate MX4 (M = Mn, Co, Cu; X = Cl, Br) anions having magnetic moment are prepared to study magnetic interaction between the conduction-electron spins on organic molecules and localized magnetic moments on inorganic counter anions. Magnetization and static susceptibility are measured between 2 and 300 K and electron paramagnetic resonance (EPR) spectra are observed between 4 and 300 K. A large shift of the resonance field of BEDT-TTF+ radical is found out in BEDT-TTF-MnCl4 and BEDT-TTF-CoCl4. EPR spectra characteristic of low-dimensional diffusive spin system are observed in TTF-MnCl4.

X‐Ray Microprobe Analyses of Vacuoles of Spruce Needle Mesophyll, Endodermis and Transfusion Parenchyma Cells at Different Seasons of the Year*

AbstractThe needles of an outdoor‐grown healthy Picea abies (L.) Karst. tree were routinely investigated from bud break up to 16 months thereafter. Transmission electron microscopical (TEM) and cryoscanning electron microscopical (CSEM) techniques were used for structural observations. Energy dispersive microanalyses (EDX) on bulk‐frozen hydrated specimens served for direct determination of element levels in the vacuoles of the mesophyll, endodermis and transfusion parenchyma cells.Both, CSEM and TEM micrographs show comparable seasonal variations e.g. in chloroplast structure and in vacuolar inclusions. EDX‐analyses clearly point out that high Mg concentrations are characteristic of mature endodermis cells. Conversely, K concentrations incline to become lower in the maturing endodermis than in the surrounding tissues. The elements P and S represent the major part of the potentially inorganic counterions for Mg and K. It is concluded that the endodermis cells serve as a storage buffer for maintaining homeostasis of Mg and S levels in the adjacent cells throughout the year.

Study of the electrochromism of polypyrrole/dodecylsulfate in aqueous solutions

Galvanostatic synthesis of polypyrrole on indium tin oxide (ITO)-coated glass electrodes at low current density in an aqueous solution containing sodium dodecylsulfate produces thin electrochromic films. The white light film transmittance passes from 50% to 98% during cycling from −0.9 to 0.6 V vs sce with color changes from brown to violet and finally to yellow. Absorption spectra at different potentials and change of transmittance at different wavelengths as a function of potential are furnished. The polypyrrole/dodecylsulfate films show a higher cyclability than polypyrrole obtained with other inorganic counter-ions.

Surface modification of montmorillonite in aqueous dispersions with hexadecylpyridinium chloride

The addition of organic cationic compounds to an aqueous suspension of a clay modifies the surface properties of the particles, and makes them wettable by organic solvents rather than by the water. The organic cations are adsorbed on the edges of the clay particles, exchanging the previous inorganic counter-ion. This is due to a strong preference of the clay for the organic cation until all the available sites will be exchanged and the clay becomes lipophilic. The stability of the resulting dispersions in oil depends strongly on the ratio between organic cation and clay. The optimum ratio is displayed near the equivalent point of ionic exchange of the clay (c.e.c.), after which a peptization occurs and the clay again becomes lipophobic and unsuitable for the dispersion of the clay in organic solvents. In this paper we describe the study of the surface changes and the rheological properties of a system composed of a water dispersion of ammonium montmorillonite, in relation to the addition of hexadecyl pyridinium chloride. The UVP (ultrasonic vibration potential) technique has been employed. The data obtained are in agreement with the rheological measurements (zero shear viscosity, pseudo-newtonian viscosity). The flocculation-deflocculation process occurring during the addition of the organic cation is discussed.

Gasification of agricultural residues (biomass): influence of inorganic constituents

Four different biomass samples are included in this study, viz., sphagnum peat, wheat straw, sugar beet pulp, and potato pulp. They were chosen to represent a wide range of plant origin and inorganic content. This paper represents a preliminary investigation of an approach based on pyrolysis of biomass to produce volatile products and chars, followed by gasification of the chars. The particular interest lies in the investigation of the influence of the indigenous metal ions on the rate of gasification. Carbon dioxide has been used for the gasification, and the biomass was analyzed for nine metals, uronic acids (which are implicated in the binding of inorganic counterions), protein, and Klason lignin. The highest individual metal ion content was 13,964 ppm of potassium in potato pulp, and the gasification rates, under constant conditions, covered up to a 20-fold range, with char from potato pulp being the most readily gasified and char from peat the most resistant. The correlation of gasification rates with content of the major metal ions (alkali metals and alkaline earths) was poor. However, a high level of correlation was observed when wheat straw was omitted. It is speculated that the latter biomass may be anomalous with respect tomore » the other three because of its high silica content.« less

Studies in reversed-phase ion-pair chromatography : V. Simultaneous effects of the eluent concentration of the inorganic counter ion and the surface concentration of the pairing ion

Retention data of the positively charged adrenaline ion, when plotted against the surface concentration of the adsorbed alkysulphonate pairing ion and the mobile-phase concentration of the inorganic counter ion (sodium), fall on a common retention surface, irrespective of the chain length of the pairing ion used. This common retention surface can be used to reconcile the apparently conflicting reports on the effects of the concentration and chain length of the alkylsulphonate pairing ion and the concentration of the inorganic counter ion. It can also be used for a better understanding and control of both retention and separation selectivity in reversed-phase ion-pair chromatography.

Counterion lyotropy and micelle formation

Decyltrimethylammonium micelles with 12 univalent inorganic counterions ( X −) have been characterized by light scattering in 0.5000 m solutions of Na X at 25°C, permitting direct comparisons with about 50 organic counterions previously studied under the same conditions. For the inorganic series, CMC values are correlated with the lyotropic numbers of the counterions and with the electrocapillary maxima of mercury in 0.5000 m Na X solutions. Although literature data on anion hydration are, in most cases, uncertain estimates, there is sufficient correlation of CMC with hydration enthalpy and with the change of size of the anion upon hydration to suggest that counterions that are highly effective in promoting micellization are those that interact the least strongly with water. Refractive index data do not sustain the hypothesis that polarizability of the counterion is a significant factor in micelle formation. Thiocyanate ion induces the formation of remarkably large micelles.

Magnetic properties of some exchange coupled [Ni(mnt)2]− dimers

The metal dithiolenes exhibit interesting solid state properties owing to the presence of columnar crystallographic packing. Particularly, thebis(maleonitriledithiolato)-nickel(III) systems with a variety of organic and inorganic counter ions seem to possess low-dimensional magnetic interactions and charge-transfer properties. The metal chelates show strong alternation in their packing and result in reduced magnetic moments as a consequence of antiferromagnetic exchange coupling between the pairs. We have studied a few interesting dimers through x-ray structure and magnetic susceptibility measurements and the results are used to arrive at a correlation between the observed magnetic behaviour and the structure of the dimeric units.

Construction and analytical applications of a chloranilate sensing liquid membrane electrode

The construction and some analytical applications of a liquid ion-selective electrode for chloranilates are described. Various salts of chloranilic acid with different large organic counter cations were prepared and tested as liquid ion exchangers. A detailed description of the preparation of the liquid ion exchanger, the procedure for the preparation of the electrode and its main characteristics are also given. The electrode was applied to the determination of the solubility constants (Ksp) of 13 salts of chloranilic acid with organic or inorganic counter cations. Sulphates in turbid samples can also be determined indirectly. An accuracy of better than 1% and a reproducibility (relative standard deviation) of 0.5% were achieved in the analysis of soluble sulphates and pharmaceutical products.

Polypyrrole-phthalocyanine

Polypyrrole films incorporating sulfonated phthalocyanines have been synthesized on Pt and indium-tin-oxide electrodes from aqueous solution. We report on the spectroelectrochemical and stability properties of the films incorporating tetra- and mono-sulfonated cobalt-phthalocyanine and tetra-sulfonated metal-free phthalocyanine. The films are strongly electrochromic and have four distinctly different color stages in the potential range 1.2 V to −1.6 V versus SCE. The films are more stable as electrodes than polypyrrole complexed with inorganic counterions and show a higher degree of crystallinity.

Identification and quantification of metabolite conjugates of activated cyclophosphamide and ifosfamide with mesna in urine by ion-pair extraction and fast atom bombardment mass spectrometry.

The high bladder toxicity of the alkylating oxazaphosphorine anticancer drugs, cyclophosphamide and ifosfamide is effectively reduced by the concomitant administration of mesna (sodium 2-mercaptoethane sulphonate). The formation and rapid urinary excretion of conjugates of the activated (4-hydroxylated) oxazaphosphorine metabolites with mesna has been suggested as the pharmacological basis for the selective detoxification, but separation and identification of such metabolites in vivo have been extremely difficult due to their high polarity and chemical lability. In this study an ion-pair extraction procedure in combination with positive and negative ion fast atom bombardment mass spectrometry has been developed which enabled the identification and quantification of the conjugation products of activated oxazaphosphorine metabolites with mesna in urine. The conjugates extracted as the tetra-n-butylammonium salts are directly identified by their characteristic positive molecular ion adducts and fragment ions, and the corresponding abundant molecular anions. The pattern of molecular and fragment ion formation was established by comparison of the fast atom bombardment mass spectra of synthetic cyclophosphamide-mesna conjugates with various organic and inorganic counter ions. The ifosfamide-4-(2-thioethylsulphonate) (ifosfamide-mesna) conjugate was identified as a metabolite in the urine of rats, and in patients after administration of the combination, ifosfamide + mesna. By means of a two-step extraction and with the use of suitable analogues as internal standards, procedures for the quantification of parent oxazaphosphorine and of oxazaphosphorine-mesna conjugates by negative ion fast atom bombardment mass spectrometry have been developed, and first examples for the determination of excretion kinetics are described.