Conventional Anion Research Articles

Characterization of a novel voltage-dependent outwardly rectifying anion current in Caenorhabditis elegans oocytes

An inwardly rectifying swelling- and meiotic cell cycle-regulated anion current carried by the ClC channel splice variant CLH-3b dominates the whole cell conductance of the Caenorhabditis elegans oocyte. Oocytes also express a novel outwardly rectifying anion current termed I(Cl,OR). We recently identified a worm strain carrying a null allele of the clh-3 gene and utilized oocytes from these animals to characterize I(Cl,OR) biophysical properties. The I(Cl,OR) channel is strongly voltage dependent. Outward rectification is due to voltage-dependent current activation at depolarized voltages and rapid inactivation at voltages more hyperpolarized than approximately +20 mV. Apparent channel open probability is zero at voltages less than +20 mV. The channel has a 4:1 selectivity for Cl(-) over Na(+) and an anion selectivity sequence of SCN(-) > I(-) > Br(-) > Cl(-) > F(-). I(Cl,OR) is relatively insensitive to most conventional anion channel inhibitors including DIDS, 4,4'-dinitrostilbene-2,2'-disulfonic acid, 9-anthracenecarboxylic acid, and 5-nitro-2-(3-phenylpropylamino)benzoic acid. However, the current is rapidly inhibited by niflumic acid, metal cations including Gd(3+), Cd(2+), and Zn(2+), and bath acidification. The combined biophysical properties of I(Cl,OR) are distinct from those of other anion currents that have been described. During oocyte meiotic maturation, I(Cl,OR) activity is rapidly downregulated, suggesting that the channel may play a role in oocyte Cl(-) homeostasis, development, cell cycle control, and/or ovulation.

Microsolvation effects on the electron capturing ability of thymine: Thymine-water clusters

The effects of solvation on the stability of thymine and its negative ion have been investigated by explicitly considering the structures of complexes of thymine with up to five water molecules and the respective anions at the B3LYP/DZP++ level of theory. The vertical detachment energy of thymine was predicted to increase gradually with the hydration number, consistent with experimental observations from a photodetachment-photoelectron spectroscopy study J. Schiedt et al., [Chem. Phys. 239, 511 (1998)]. The adiabatic electron affinity of thymine was also found to increase with the hydration number, which implies that while the conventional valence anion of thymine is only marginally bound in the gas phase, it may form a stable anion in aqueous solution.

Mass spectrometric identification of novel arsinothioyl-sugars in marine bivalves and algae

Following recent reports on the detection of the new group of thioarsenosugars in marine molluscs we have developed two chromatographic methods in order to explore the presence of additional species of this group in biological samples. A series of thioarsenosugar standards, containing four different thioarsenosugars in total, was prepared and used for method optimization. First, conventional anion exchange chromatographic conditions were modified to achieve efficient elution of the thioarsenosugars. This required relatively high contents of methanol in the mobile phase (up to 40%). Online hyphenation with electrospray tandem mass spectrometry provided good quality product ion mass spectra for the thioarsenosugars. These allowed the generation of collision induced dissociation breakdown curves for each compound which finally resulted in the development of a very sensitive and specific selected reaction monitoring approach. However, the high amount of methanol used with this method was not optimum for direct hyphenation with inductively coupled plasma mass spectrometry (ICP-MS) without a specially adapted interface. Therefore, reversed phase anion pairing HPLC with a low methanol content (5%) in the mobile phase was developed and used in this case. The combined application of both analytical techniques revealed the presence of two novel thioarsenosugars in marine bivalves and marine algae. Moreover, this is the first time that the detection of thioarsenosugars in marine algae is reported.

Novel bromide anion conducting refractory solid electrolytes based on lanthanum oxybromide

A new type of high bromide anion conducting solid was artificially designed with the solids based on lanthanide oxybromide (LnOBr). LnOBr is selected as it is insoluble in water and also highly stable at temperatures around 800°C. The enhancement of Br− anion conductivity was successfully realized by creating Br− ion vacancies by doping divalent cation in the Ln site of the LnOBr host lattice. The Br− anion conductivity was the highest among the conventional bromide anion conducting solids such as Pb0.99K0.01Br1.99 (373°C) and CsPbBr3 (500°C) which contain toxic lead in them. The Br− anion conductivity of LnOBr based solid enters into the practically useful region (σ > 10−3 Sċcm−1).

Separation of rare earths in nitric acid medium by a novel silica-based pyridinium anion exchange resin

To separate rare earths in nitric acid medium by anion exchange process, a novel silica-based macro-reticular anion exchange resin (SiPyR-N4) with pyridinium as functional group has been synthesized. It was found that the SiPyR-N4 resin exhibits a quite strong adsorption for some rare earths especially the light rare earth elements such as La, Ce, Pr, Nd and Pm whose distribution coefficients onto SiPyR-N4 reach 10–25 dm 3/kg-resin, which are much higher than the reported values for these elements with conventional anion exchange resins. The results from the column experiments show that the rare earths can be separated into the three groups: light, moderate and heavy rare earths and, a perfect separation between La–Pr group and Sm–Gd group can be achieved.

Separation of Burnup Monitors in Spent Nuclear Fuel Samples by Liquid Chromatography

A coupled column liquid chromatography system was applied for the separation of the burnup monitors in spent nuclear fuel sample solutions. A reversed phase column was studied for the adsorption behavior of uranyl ions using alpha-hydroxyisobutyric acid as an eluent and used for the separation of plutonium and uranium. A cation exchange column prepared by coating 1-eicosylsulfate onto the reversed phase column was used for the separation of the lanthanides. In addition, retention of Np was checked with the reversed phase column and cation exchange column, respectively, according to the oxidation states to observe the interference effect for the separation of burnup monitors. This chromatography system showed a great reduction in separation time compared to a conventional anion exchange method. A good agreement from the burnup data was obtained between for this method and a conventional anion exchange method to within 1% of a difference for the spent nuclear fuel samples of about 40 GWD/MTU.

Lithium-pyrazole-3,4,5-tricarbonitrile: Ion Pairing and Lithium Ion Affinity Studies

Negative charge stabilized by ring delocalization on five-membered rings is a practical and theoretically interesting alternative to conventional fluorine-based anions. Coordination of the lithium cation to the pyrazole-3,4,5-tricarbonitrile (PATC) anion was studied using vibrational spectroscopy (Raman and IR) and ab initio SCF-MO Hartree−Fock (HF) calculations. Four 1:1 ion pair geometries were found, one being energetically more stable. By comparing theoretical spectra with both IR and Raman spectra of salt solutions, it was found that the lithium ion favors bidentate coordination to the ring nitrogen atoms, as suggested by the binding energies. Finally, comparisons were made with previously calculated coordination strengths for other similar lithium anion 1:1 systems.

Environmental applications of a cryptand adjustable-capacity anion-exchange separator

A 2.2.2 cryptand-based anion exchanger was recently introduced as a commercial product. This new technology relies on a covalently bonded 2.2.2 cryptand, which allows one to selectively control the capacity of the column simply by the choice of eluent. This provides the analyst with more flexibility over conventional anion exchangers to suit the needs of the sample matrix. Since that time, a 2.2.1 version has also been developed and studied. In this paper we will compare the two types of columns and choose the best one for analyzing several environmental samples.

Influence of different initiators on the adhesion properties of photopolymerized epoxides on gold and silicon

Photocuring of epoxides proceeds by a cationic mechanism. The required photoinitiators are iodonium or sulfonium salts with non-nucleophilic anions. The influence of different photoinitiators on the adhesion properties of both a rigid and a soft epoxide is examined. Depending on the substrates to be joined, different decomposition products of the initiators are concentrated in the interphase. This accumulation of decomposition products in the interphase leads to a decreased adhesion. On gold surfaces the sulfur of sulfonium salts is concentrated as expected. But surprisingly the iodine of the iodonium salts is also concentrated on gold. It could be shown by immobilization experiments that organic iodine compounds with the iodine in any oxidation state reacted with gold surfaces. Due to this reaction iodide anions are formed. On silicon surfaces the fluorine of the anions PF6 - and SbF6 - is concentrated due to the high affinity of silicon for fluorine. The iodonium salt with [B(C6F5)4]anion contains no fluorine able to react with the silicon. Therefore, the fluorine cannot be concentrated in the interphase and the joints prepared with the soft epoxide containing this initiator have a higher shear strength compared to adhesives with conventional anions.

Adsorption Behavior of Various Metal Ions in Nitrite Medium and Separation of Some Metals by Anion Exchange

The purpose of this work is to investigate the adsorption behavior of various metals ions and the possibility of their separation in nitrite medium by anion exchange. Distribution coefficients of about 40 metals from nitrite solution onto a conventional anion exchanger (IRA-900) and a new type anion exchanger (AR-01) containing benzimiclazoles as functional group were systematically measured. Based on the different adsorbability, some metal pairs such as Zn (II) /Cd (II) and Ga (III) /In (III) in NaNO2-HNO3 solution, were successfully separated from each other by column chromatography.

Studies on the Adsorption of Uranium and Fission Produet Elements from Nitric Acid Medium by Novel Silica-Based Polyvinylpyridine Anion Exchange Resin

To develop a new ion exchange process for the separation of uranium from fission products we have synthesized a novel silica-based macro-reticular polyvinylpyridine anion exchange resin. This resin has been used for the adsorption studies of uranium and some of the fission products from nitric acid medium. The distribution coefficient values for the adsorption of uranium in both tetravalent and hexavalent oxidation states were measured with the new resin and these values have been compared with the literature values for conventional anion exchange resin with quaternary ammonium as functional group. The newly synthesized silica-based macro-reticular polyvinyl pyridine anion exchange resin has the particles diameter of 50 μm, which results in fast adsorption kinetics, low swelling and pressure drop as compared to a conventional polymer based anion exchange. The distribution coefficient values for tetravalent uranium are considerably higher as compared to most of the fission products. The results indicate that complete separation of U(IV) from most fission products can be achieved.

Multipole-Bound Molecular Negative Ions

Within the framework of a simple electrostatic model, as compared to recent experimental results, we here discuss the stability of very weakly bound molecular negative ions. In contrast with the case of conventional valence anions, the excess electron is then located in a very diffuse orbital and is mainly bound by electrostatic dipolar, quadrupolar, and polarization forces, at large distances from the neutral molecular core. By fitting a single repulsion parameter of the model to the available experimental data, it is possible to make quantitative predictions of the excess-electron binding energies in these species. Critical values of the dipole moment, quadrupole moment or polarizability required for the observation of stable multipole-bound negative ions are predicted and compared to available experimental data and ab initio calculations.

Radiochemical determination of 241Am and Pu(alpha) in environmental materials.

Americium-241 and plutonium determinations will become of greater importance over the coming decades as 137Cs and 241Pu decay. The impact of 137Cs on environmental chronology has been great, but its potency is waning as it decays and diffuses. Having 241Am and Pu as unequivocal markers for the 1963 weapon fallout maximum is important for short time scale environmental work, but a fast and reliable procedure is required for their separation. The developed method described here begins by digesting samples using a lithium borate fusion although an aqua regia leachate is also effective in many instances. Isolation of the Am and Pu is then achieved using a combination of extraction chromatography and conventional anion exchange chromatography. The whole procedure has been optimized, validated, and assessed for safety. The straightforwardness of this technique permits the analysis of large numbers of samples and makes 241Am-based techniques for high-resolution sediment accumulation rate studies attractive. In addition, the technique can be employed for the sequential measurement of Pu and Am in environmental surveillance programs, potentially reducing analytical costs and turnround times.

The Study of Pretreatment for the Determination of the Conventional Anion in Sea Water by IC——the Method of Electrolysing Argentine Electrode

The Study of Pretreatment for the Determination of the Conventional Anion in Sea Water by IC——the Method of Electrolysing Argentine Electrode

Comparison of particulate and continuous-bed columns for protein displacement chromatography

A conventional anion exchange column packed with porous particles (BioScale Q2), and a novel continuous-bed column (UNO™ Q1) were compared for displacement separation of dairy whey proteins with polyacrylic acid as displacer. The steric mass action model was investigated as a means to aid and accelerate this development. Characteristic charges and steric factors were measured for the proteins and the displacer according to the model, and used together with the affinity constant derived from the adsorption isotherms for simulations, as well as for the construction of the affinity and operating regime plots. If possible, the latter two were used to select conditions for the actual experiments. In the case of the particle-based column, experimental results and simulations did not agree. In addition, the operating regime plot could not be constructed. The affinity plot did predict the order in the displacement train correctly, but gave misleading information concerning the possible effect of a change in displacer concentration. This is taken to be a result of the porous nature of the particles, which handicaps, to some extent, the interaction of the proteins and the displacer molecules with the adsorptive surface. Results were considerably better in case of the continuous-bed column, where there is no intraparticulate surface.

Ligand Separation with a Copper(II)-Loaded Polymeric Ligand Exchanger

The present study characterizes a new polymeric ligand exchanger (PLE) for enhanced separation of trace anionic ligands, and investigates related interfacial chemistry. Compared to conventional anion exchangers, the PLE exhibited significantly different selectivity sequence and elution profiles, which may be utilized in enhancing selective capture of target solutes and/or chromatographic separation of anionic ligands. Experimental data indicate that the exchanger phase pH is significantly higher across the resin−solution interface caused by the Donnan co-ion exclusion effect. Intraparticle diffusion appears to be the rate-limiting step during a typical fixed-bed column run. A linear free-energy relationship (LFER) was derived and experimentally validated between the binary separation factors and the aqueous phase metal−ligand stability constants.

An optimised and robust method for the determination of uranium and plutonium in aqueous samples

The paper describes a method for the separation of uranium and plutonium isotopes using anion exchange resin and UTEVA ™ resin in stacked sequential columns for routine analysis of river water and liquid effluent samples. The optimisation of the UTEVA ™ column for separation of U is described and compared with the conventional anion exchange technique for the separation of U from Fe. The stacked anion exchange and UTEVA ™ column configuration facilitates a more rapid and efficient separation of Pu and U and also reduces the quantity of reagents required for the separation.

Electrodialysis of acetate fermentation broths.

Electrodialysis (ED) shows good potential for downstream processing of acetate fermentation broths, to separate acetic acid while unreacted glucose and other nutrients are partially recycled back to the fermenter. With conventional anion- and cation-exchange membranes, higher current increased acetate flux, water flux, and energy consumption. Multiple ED stacks connected in series with unequal initial volumes for a batch process maximized acetate concentration in the concentrating stream to 134 g/L calcium-magnesium acetate (CMA) in the fermentation broth at pH 6.8. Back-transport of acetate from the product into the feed stream and water transport limit the maximum concentration possible. Cost of ED is about 295 dollars/ton acetate for the CMA broth.

Separation of plasmid DNA from protein and bacterial lipopolysaccharides using displacement chromatography.

The preparation of plasmid DNA at large scale constitutes a pressing problem in bioseparation. This paper describes a first investigation of displacement chromatography as a means to separate plasmid DNA (4.7 kb) from E. coli lipopolysaccharides and protein (holo transferrin), respectively. Displacement chromatography has advantages in this regard, since the substance mixture is resolved into rectangular zones of the individual components rather than into peaks. Thus a higher total concentration can be maintained in the pooled product fractions. Hydroxyapatite (type I and II) and anion exchange stationary phases were included in the experiments. In addition to a conventional anion exchange column packed with porous particles, the recently introduced continuous bed UNOTM anion exchange column was investigated. No DNA purification was possible with either hydroxyapatite material. Conventional particle based columns in general were not suited to the separation of any two substances varying considerably in molecular mass, e.g. plasmid DNA and standard protein. Presumably, the direct competition for the binding sites, which is essential in displacement chromatography, was restricted by the size dependency of the accessible stationary phase surface area in this case. Better results were obtained with the continuous bed column, in which the adsorptive surface coincides with the walls of the flow through pores. As a result the accessible surface does not vary as much with the size of the interacting molecules as for the conventional stationary phase materials. Sharper transitions were also observed between substance zones recovered from the UNOTM column. The steric mass action model was used to aid method development in case of the anion exchange approach. While further research in obviously necessary, displacement chromatography on continuous bed columns has been shown to be capable of separating plasmid DNA from typical impurities.

Two thermodynamically stable states inSiO−andPN−

In contrast to the well-known CO and ${\mathrm{N}}_{2}$ molecules, isoelectronic SiO and PN form thermodynamically stable conventional (valence) and dipole-bound anion states upon attachment of an extra electron. According to the results of our high-quality ab initio calculations, binding energies of the electron in these states are 38 and 1.6 meV $({\mathrm{SiO}}^{\mathrm{\ensuremath{-}}})$ and 76 and 1.0 meV $({\mathrm{PN}}^{\mathrm{\ensuremath{-}}}),$ respectively. Dissociation trends of the ${\mathrm{SiO}}^{\mathrm{\ensuremath{-}}}$ and ${\mathrm{PN}}^{\mathrm{\ensuremath{-}}}$ anions are discussed.