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High-performance layer electrochromatography (HPLEC) combines the advantages of overpressured-layer chromatography (OPLC) and pressurized planar electrochromatography (PPEC) while overcoming some of their limitations. HPLEC equipment can work in various HPLEC, OPLC, and PPEC modes. The equipment enables HPLEC analysis also with an electroosmotic effect directed against the hydrodynamic flow of the mobile phase. The change in the electric field direction in the separation system does not result in a change in either the direction of the mobile phase flow or the direction of solute migration. The hydrodynamic flow generated by the pump dominates the electroosmotic effect and enables separation against the direction of the latter. Reversed-polarization HPLEC may be advantageous for the analysis of anionic compounds, as it facilitates faster and more selective separation than OPLC performed in similar conditions. This separation mode provides a new possibility to develop and optimize separation methods by performing separation against the electroosmotic effect and without need of any modification of the adsorbent surface. A drawback of this separation mode is the increase in the backpressure at the mobile phase inlet and the limitation of the mobile phase flow rate. Currently, contrary to the single-channel mode, multi-channel reverse-polarity HPLEC still requires some technical and methodological improvements. [ABSTRACT FROM AUTHOR]

In‐situ interfacial polymerization technique is developed to prepare monovalent anion‐permselective membranes (MAPMs). The introduction of multi‐hydroxyl (OH) and cationic groups in the base membrane provide suitable routes towards the monovalent anion transport. Only trimesoyl chloride is employed to generate a crosslinked polyester layer on membrane surface. The ISIP transforms the surface of anion exchange membranes into a dense and negatively charged layer to promote the ion permselectivity. The modified membranes show a high limiting current density and low membrane resistance of 4.7 Ω cm2. The resultant membranes exhibit a high Cl− flux of 6.3 × 10−8 mol cm−2 s−1 and a high permselectivity of ~60 for Cl−/SO42−. The findings demonstrate the ISIP technique having great potentials for the fabrication of highly permselective MAPMs. [ABSTRACT FROM AUTHOR]

Capillary electrophoresis (CE) has the advantage of rapid anion analysis, when employing a reverse electroosmotic flow (EOF). The conventional CE method utilizes dynamic coatings with surfactants like cetyltrimethylammonium bromide (CTAB) in the run buffer to reverse the EOF. However, this method suffers from very slow equilibration leading to drifting effective migration times of the analyte anions, which adversely affects the identification and quantification of peaks. Permanent coating of the capillary surface may obviate this problem but has been relatively little explored. Thus, permanent capillary surface modification by the covalent binding of 3-aminopropyltriethoxysilane (APTES) was studied as an alternative. This study investigates the effect of APTES concentration for surface functionalization on EOF mobility, separation efficiency, and reproducibility of anion separation. The performance data was complemented by X-ray photoelectron spectroscopy (XPS) and contact angle (CA) measurements. The XPS measurements showed that the coverage with APTES was dependent on its concentration in the coating solution. The XPS measurements correlated well with the EOF values determined for the capillaries tested. A standard mixture of 21 anions could be baseline separated within 10 min in the capillaries with lower EOF, but not in the capillary with the highest EOF as the residence time of the analytes was too short in this case. Compared to conventional dynamic coating with CTAB, APTES-functionalized capillaries provide faster equilibration and long-term EOF stability. The application of APTES-functionalized capillaries in analyzing different beverages demonstrates the precision, reliability, and specificity in determining organic anions, providing valuable insights of their compositions. APTES coating on capillaries provides a facile approach to achieve a permanent reversal of the stable EOF to determine anions. The control of the coverage via the concentration of the reagent solution allows the tailoring of the EOF to different needs, a faster EOF for less complex samples where resolution is not challenging, while a lower EOF for higher complex samples where the focus is on separation efficiency. This enhancement in efficiency and sensitivity has been applied to analyzing organic acids in several beverages. [Display omitted] • APTES functionalization enhances anion separation in reversed electroosmotic flow. • APTES modification shows superior performance compared to dynamic coating. • Functionalized capillaries allowed the separation of 21 anions with C4D detection. • Organic acids were determined successfully in 12 beverage products. [ABSTRACT FROM AUTHOR]

High-performance layer electrochromatography (HPLEC) combines the advantages of overpressured-layer chromatography (OPLC) and pressurized planar electrochromatography (PPEC) while overcoming some of their limitations. HPLEC equipment can work in various HPLEC, OPLC, and PPEC modes. The equipment enables HPLEC analysis also with an electroosmotic effect directed against the hydrodynamic flow of the mobile phase. The change in the electric field direction in the separation system does not result in a change in either the direction of the mobile phase flow or the direction of solute migration. The hydrodynamic flow generated by the pump dominates the electroosmotic effect and enables separation against the direction of the latter. Reversed-polarization HPLEC may be advantageous for the analysis of anionic compounds, as it facilitates faster and more selective separation than OPLC performed in similar conditions. This separation mode provides a new possibility to develop and optimize separation methods by performing separation against the electroosmotic effect and without need of any modification of the adsorbent surface. A drawback of this separation mode is the increase in the backpressure at the mobile phase inlet and the limitation of the mobile phase flow rate. Currently, contrary to the single-channel mode, multi-channel reverse-polarity HPLEC still requires some technical and methodological improvements.

Supramolecular hosts bind to inorganic anions at a fast rate and select them in proportion with thermodynamic stability of the corresponding [anion⊂host] complexes, forming in a reversible manner. In this study, we describe the action of hexapodal capsule 1 and its remarkable ability to select anions based on a large span of rates by which they enter this host. The thermodynamic affinity of 1 toward eighteen anions extends over eight orders of magnitude (0

The recognition and separation of anions attracts attention from chemists, materials scientists, and engineers. Employing exo‐binding of artificial macrocycles to selectively recognize anions remains a challenge in supramolecular chemistry. We report the instantaneous co‐crystallization and concomitant co‐precipitation between [PtCl6]2− dianions and cucurbit[6]uril, which relies on the selective recognition of these dianions through noncovalent bonding interactions on the outer surface of cucurbit[6]uril. The selective [PtCl6]2− dianion recognition is driven by weak [Pt−Cl⋅⋅⋅H−C] hydrogen bonding and [Pt−Cl⋅⋅⋅C=O] ion–dipole interactions. The synthetic protocol is highly selective. Recognition is not observed in combinations between cucurbit[6]uril and six other Pt‐ and Pd‐ or Rh‐based chloride anions. We also demonstrated that cucurbit[6]uril is able to separate selectively [PtCl6]2− dianions from a mixture of [PtCl6]2−, [PdCl4]2−, and [RhCl6]3− anions. This protocol could be exploited to recover platinum from spent vehicular three‐way catalytic converters and other platinum‐bearing metal waste. [ABSTRACT FROM AUTHOR]

High resolution photoelectron spectra of the vinoxide anion are obtained by slow electron velocity-map imaging. Transitions between the anion X 1A′ ground electronic state and the radical X 2A″ and à 2A′ states are observed. This experiment yields a precise value of 1.8250±0.0012 eV for the adiabatic electron affinity and 0.996±0.003 eV for the Ã-X term energy of the vinoxy radical. Franck–Condon simulations of the X 2A″←X 1A′ transition are performed at varying levels of approximation. Full treatment with Duschinsky rotation is necessary to reproduce experimental results. Comparison of the experimental and simulated spectra leads to the assignment of previously unresolved transitions, notably between levels of a″ symmetry. [ABSTRACT FROM AUTHOR]

This study examined the anion clusters of pyrene (Py) by mass spectrometry, photoelectron spectroscopy, and theoretical calculations. The photoelectron spectra of Pyn- (n=1–4) were obtained at various photon energies. A change in photodetachment wavelength resulted in a large change in the relative intensities of vibrational progression in the photoelectron spectra. It is proposed that the observed modulation of the Franck–Condon factors by the different photon energies reflects autodetachment via the excited states of anion. The photoelectron spectra of Pyn- at 355 nm showed a broad band structure between the S0 and T1 states, which is also due to the autodetachment via a Feshbach resonance state. The photoelectron spectra of Py2- suggest the presence of a unique dimeric interaction between the two pyrene moieties, whereas the spectral features of Py3- are similar to those of Py1-. The stable structures of Py2- and Py3- obtained by density functional theory calculations support the experimental findings, where different intermolecular interactions govern the stabilization of these two species. [ABSTRACT FROM AUTHOR]

This paper attempts to elucidate the number and nature of the hydration spheres around the proton in an aqueous solution. This phenomenon was studied in aqueous solutions of selected acids by means of Fourier transform infrared spectroscopy of semiheavy water (HDO), isotopically diluted in H2O. The quantitative version of difference spectrum procedure was applied for the first time to investigate such systems. It allowed removal of bulk water contribution and separation of the spectra of solute-affected HDO. The obtained spectral data were confronted with ab initio calculated structures of small gas-phase and polarizable continuum model (PCM) solvated aqueous clusters, H+(H2O)n, n=2–8, in order to help in establishing the structural and energetic states of the consecutive hydration spheres of the hydrated proton. This was achieved by comparison of the calculated optimal geometries with the interatomic distances derived from HDO band positions. The structure of proton hydration shells outside the first hydration sphere essentially follows the model structure of other hydrated cations, previously revealed by affected HDO spectra. The first hydration sphere complex in diluted aqueous solutions was identified as an asymmetric variant of the regular Zundel cation [The Hydrogen Bond: Recent Developments in Theory and Experiments, edited by P. Schuster, G. Zundel, and C. Sandorfy (North-Holland, Amsterdam, 1976), Vol. II, p. 683], intermediate between the ideal Zundel and Eigen structures [E. Wicke et al., Z. Phys. Chem. Neue Folge 1, 340 (1954)]. Evidence was found for the existence of strong and short hydrogen bonds, with oxygen-oxygen distance derived from the experimental affected spectra equal 2.435 Å on average and in the PCM calculations about 2.41–2.44 Å. It was also evidenced for the first time that the proton possesses four well-defined hydration spheres, which were characterized in terms of hydrogen bonds’ lengths and arrangements. Additionally, an outer hydration layer, shared with the anion, as well as loosely bound water molecules interacting with free electron pairs of the central complex were detected in the affected spectra. [ABSTRACT FROM AUTHOR]

The cross section for bond breaking at the site of a dissociative temporary negative ion state through the dissociative electron attachment process can be considerably enhanced by the presence of a second longer-lived temporary negative ion state elsewhere in the molecule, even one quite remote from the first. In a series of chloroalkenes possessing both C–Cl and C==C bonds separated by various distances, we show that the cross sections are determined by the lifetime of the lower anion state created by the mixing of the anion states of these two moieties, with the wave function’s coefficients giving the probability that the electron is located at the dissociative site. Furthermore, the lifetime of the composite anion state can be expressed in terms of these same coefficients and the lifetimes of the unmixed resonances. We also discuss how these results may give insight into the means by which strand breaks are induced in DNA by the attachment of slow electrons. [ABSTRACT FROM AUTHOR]

High resolution anion photodetachment spectra are presented for the methoxide anion and its fully deuterated counterpart. The spectra were obtained with slow electron velocity-map imaging. Improved electron affinities are determined for CH3O as 1.5690±0.0019 eV and for CD3O as 1.5546±0.0019 eV. The spectra resolve many features associated with spin-orbit and vibronic coupling that were not seen in previous photodetachment studies. Photoelectron angular distributions taken as a function of detachment wavelength for the ground vibronic state transitions are recorded and are consistent with the removal of a nonbonding, p-type electron localized on the oxygen atom. Several hot bands and sequence bands are observed for the first time, providing insight into the vibrational structure of the methoxide anion. The results are compared to recent calculations of the anion photoelectron spectra that incorporate bilinear coupling terms among the methoxy vibrational modes and are found to be in reasonable agreement. [ABSTRACT FROM AUTHOR]

Photoelectron images are recorded in the photodetachment of two series of cluster anions, (CO[sub 2])[sub n][sup -], n=4–9 and (CO[sub 2])[sub n][sup -]·H[sub 2]O, n=2–7, with linearly polarized 400 nm light. The energetics of the observed photodetachment bands compare well with previous studies, showing evidence for switching between two anionic core structures: The CO[sub 2][sup -] monomer and covalent (CO[sub 2])[sub 2][sup -] dimer anions. The systematic study of photoelectron angular distributions (PADs) sheds light on the electronic structure of the different core anions and indicates that solvation by several CO[sub 2] molecules and/or one water molecule has only moderate effect on the excess-electron orbitals. The observed PAD character is reconciled with the symmetry properties of the parent molecular orbitals. The most intriguing result concerns the PADs showing remarkable similarities between the monomer and dimer anion cluster-core types. This observation is explained by treating the highest-occupied molecular orbital of the covalent dimer anion as a linear combination of two spatially separated monomeric orbitals. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this work, high performance cross-linked anion exchange membranes with hydrophobic side-chains were prepared via quaternization reaction and a simple heat treatment. The cross-linked membrane structure, the hydrophobic side-chain and the micro-phase separated morphology of membranes have synergistic effect on ion selective separation. Accordingly, the obtained membranes possess excellent ion perm-selectivity and considerable OH− flux. Especially, QPPO-C6-120 membrane exhibits the superior perm-selectivity of 76 for OH−/ W O 4 2 − system and high OH− flux of 2.72 × 10−7 mol cm−2 s−1 at a current density of 30 mA cm−2. XPS and 1H NMR confirmed the introduction of long side-chain and the thermo-crosslinking reaction. Meanwhile, the microstructure of membranes was investigated by XRD and SAXS. More importantly, a new perspective of mesoscales by combining the molecule structure with the microstructure of membranes is innovatively used to explore the ion separation mechanism. Image 1 • Cross-linked AEMs with hydrophobic side-chains for anion separation were fabricated. • A comprehensive study from meso-scale view for anion separation was provided. • Synthesized membranes showed high ion perm-selectivity and considerable OH− flux. [ABSTRACT FROM AUTHOR]

Electrosynthesized polypyrrole (PPy) films on PVDF/Pt support membranes were used to study electrochemically controlled transport of monovalent and divalent anions across the PPy-based membranes. The PVDF/Pt/PPy membrane separated two compartments in a transport cell and served simultaneously as the working electrode allowing electrochemical switching of PPy between its oxidized and reduced forms during the transport experiments. PPy was electrosynthesized in presence of p-toluene sulfonate, camphorsulfonate and hexafluorofosfate (doping ions) and the ion transport properties of the resulting PPy-based membranes were investigated. The morphology and elemental composition of PPy before and after the anion transport studies were studied by SEM and EDXA. The anion fluxes obtained during transport of a mixture of Cl−, NO 3 −, SO 4 2− and HAsO 4 2− across the PPy-based membranes were found to decrease in the following order: NO 3 − > Cl− » SO 4 2− > HAsO 4 2−. PPy films with the same composition as for the transport studies were also electrodeposited on glassy carbon electrodes (GC/PPy) and studied by potentiometry. The potentiometric selectivity of the GC/PPy electrodes towards Cl−, NO 3 − and SO 4 2− was found to correlate with the ion transport characteristics of the corresponding PPy membranes used in the transport cell. The PPy-based membranes allowed separation of monovalent from divalent anions. • Anion transport through polypyrrole membranes was controlled electrochemically. • Polypyrrole membranes separate monovalent anions from divalent anions. • Ion transport correlated with potentiometric selectivity for Cl−, NO 3 − and SO 4 2−. • Polypyrrole membranes can separate the toxic HAsO 4 2− from NO 3 − and Cl−. [ABSTRACT FROM AUTHOR]

Abstract Fabricating stable mono-/multi-valent anion-selective membranes with high perm-selectivity for electrodialysis (ED) applications is critical but challengeable. In this work, we have fabricated a series of novel homogeneous monovalent anion-selective amphoteric ion-exchange membranes (AIEMs, PAES-im-Xc) based on a long-side-chain type imidazolium-functionalized poly(arylene ether sulfone) cross-linked with 4,4′-diazostilbene-2,2′-disulfonic acid disodium salt (DAS) for ED. By tuning the mass percent of DAS added, low swelling ratio but appreciably high anion perm-selectivity (in Cl–/SO 4 2– system) of optimized AIEM are achieved to values of 8.0% and 47.12 at current density of 2.5 mA cm–2, respectively. In particular, at an enhanced current density of 5.0 mA cm–2, its perm-selectivity reaches 12.5, significantly outperforming commercial monovalent anion-selective Neosepta ACS (5.27). The appreciably high perm-selectivity possibly arises from pore-size sieving effect from dense matrix structure with cross-linkings and strong electrostatic repulsion between negative fixed –SO 3 – groups and negative divalent ions of SO 4 2– in feeding solution. The superior performances might be particularly interesting findings that can facilitate the development of advanced mono-/bi-valent anion-selective membranes in applications of sea water desalination, resource recovery and water treatment/pretreatment etc.. Graphic abstract fx1 Highlights • A series of novel homogeneous monovalent anion-selective AIEMs has been fabricated for ED. • By tuning the content of cross-linker, low swelling ratio but high perm-selectivity are achieved. • The optimized AIEM shows the perm-selectivity (P S O 4 2 − C l − ) of 12.5, outperforming Neosepta ACS (5.27). • Pore-size sieving effect and electrostatic repulsion contribute to high perm-selectivity a lot. [ABSTRACT FROM AUTHOR]

An analytical method was developed for the simultaneous determination of thiocyanate and iodide by reversed‐phase liquid chromatography with UV detection using imidazolium ionic liquids as mobile phase additives. The chromatographic behaviors of the two anions on a C18 column were studied and compared with four types of reagents including imidazolium ionic liquids, pyridinium ionic liquids, 4‐aminophenol hydrochloride and tetrabutylammonium as mobile phase additives. The effects of the concentrations of imidazolium ionic liquids, organic solvents and detection wavelength on separation and detection of the anions were investigated. The role of ionic liquids, retention rules and mechanisms were discussed. The separation of the anions was performed on the C18 reserved‐phase column using acetonitrile‐0.3 mmol/L 1‐amyl‐3‐methylimidazolium tetrafluoroborate (10:90, v/v) as mobile phase, with column temperature of 35°C, flow rate of 1 mL/min and detection wavelength of 210 nm. Under these conditions, the two anions can be completely separated within 6 min. The limits of detection were 0.05 mg/L. The method was applied for the determination of thiocyanate and iodide in ionic liquid samples and iodide drugs, and the spiked recoveries ranged from 97 to 101%. The method is simple, accurate and meets the requirements of quantitative analysis for thiocyanate and iodide. [ABSTRACT FROM AUTHOR]

Abstract Poly(1-vinylimidazole- co -ethylene dimethacrylate) (VIM-EDMA) monolithic stationary phase was applied for separation of inorganic anions by capillary ion chromatography (IC). The retention of inorganic anions on the VIM-EDMA column was investigated using various salt solutions as the eluent. Good separation of inorganic anions was obtained on VIM-EDMA monolithic column using NH 4 Cl as the eluent. Good mechanical stability and low swelling propensity values (0.12 and −0.02 for ACN and MeOH, respectively) were obtained. The column repeatability was also examined by determining the relative standard deviations (RSDs) of retention time and peak area of target anions. Relatively low RSDs (n = 7) of retention time (<2.3%) and peak area (<8.8%) were obtained on the VIM-EDMA column. The utilization of VIM-EDMA column for potential environmental application was also demonstrated by determining the occurrence of inorganic anions in various environmental water samples without sample preparation process. Graphical abstract fx1 Highlights • Separation of inorganic anions was achieved on VIM-EDMA column using NH 4 Cl as eluent. • Good mechanical stability and limited swelling/shrinkage of VIM-EDMA were obtained. • Good retention time/peak area repeatability was obtained on VIM-EDMA for anion separation. • VIM-EDMA column was applied for determining nitrate in environmental water samples. [ABSTRACT FROM AUTHOR]

In this study, a series of novel anion exchange membranes composed of polyvinyl alcohol (PVA) and various amount of synthesized anion exchange precursor were successfully prepared and used for acid recovery by DD process. The anion exchange precursor (Q-DAN) was synthesized through reaction of 1,5-diaminonaphthalene (DAN) and 2,3-epoxypropyltrimethylammonium chloride (EPTC) which was confirmed by proton NMR. The dosage of Q-DAN inside membrane matrix played an important role to determine the electrochemical and physicochemical properties of Q-DAN AEMs. Influences of Q-DAN and multivalent metal ions on acid recovery were elaborated in detail. Acid dialysis coefficients (U H ) values for FeCl 2 -HCl system were in the range of 0.0194–0.0295 m/h and separation factors were ranged from 27.84 to 52.60 at 25 °C. Furthermore, acid dialysis coefficient (3.28 times) and separation factor (2.84 times) were much greater than commercial membrane DF-120 (U H and S = 0.009 m/h and 18.5), respectively. Moreover, Q-DAN-4 membrane was selected to investigate the effects of multivalent metal ions on diffusion dialysis. The results showed that the presence of different metal salts in hydrochloric acid solution effect the membrane diffusivity and selectivity in diffusion dialysis process due to complexation of metal ions and acid. [ABSTRACT FROM AUTHOR]

Abstract: Recent work has identified a bis‐(p‐nitrophenyl)ureidodecalin anion carrier as a promising candidate for biomedical applications, showing good activity for chloride transport in cells yet almost no cytotoxicity. To underpin further development of this and related compounds, a detailed structural and binding investigation is reported. Crystal structures of the transporter as five solvates confirm the diaxial positioning of urea groups while revealing a degree of conformational flexibility. Structures of complexes with Cl−, Br−, NO3−, SO42− and AcO−, supported by computational studies, show how the binding site can adapt to accommodate these anions. 1H NMR binding studies revealed exceptionally high affinities for anions in DMSO, decreasing in the order SO42−>H2PO4−≈HCO3−≈AcO−≫HSO4−>Cl−>Br−>NO3−>I−. Analysis of the binding results suggests that selectivity is determined mainly by the H‐bond acceptor strength of different anions, but is also modulated by receptor geometry. [ABSTRACT FROM AUTHOR]

The aim of this work was to obtain and characterize the selectivity of a new type of ion-exchanger - porous highly basic monolith with high internal phase emulsion (HIPE) structure. Poly(HIPE)ViM monolith of bis-vinylimidazolium salts was prepared in a water-in-oil-in-water emulsion (W1/O/W2). The structure of the resulting HIPE polymer was confirmed using scanning electron microscopy (SEM). Ion-exchange ability and the selectivity of monolithic anion-exchanger were tested towards the following inorganic anions: F−, Br, Cl−, NO3−, SO42-, Mo7O246-, PO43-; and organic anions: malate, citrate, malonate, tartate, lactate and oxalate. The concentration of anions before and after the sorption was measured using ion chromatography. [ABSTRACT FROM AUTHOR]

14 C-containing dissolved organic compounds may significantly contribute to the calculated annual overall dose emanated from a deep geological repository for radioactive waste. To date, there is a general lack of knowledge concerning the transport behaviour of low molecular weight organic compounds in the geosphere. The present work is aiming at a generic approach to measure weak adsorption of such compounds onto selected clay minerals. Percolation experiments were employed to sensitively measure the retardation of low molecular weight carboxylates and alcohols in compacted illite and kaolinite as a function of the ionic strength. Detection limits of ∼10 −5  m 3  kg −1 for the involved sorption distribution coefficients were attained thereby. The adsorption of alcohols on clays was near the detection limit and assumed to occur predominately via H-bonding. The adsorption of organic anions was influenced by several factors such as molecular structure, type of clay surfaces and the chemical composition of the aqueous phase. It was found that the relative position of neighbouring hydroxyl groups strongly influenced the retardation behaviour. Alpha-hydroxylated carboxylates, such as lactate, were found to be most retarded. Ligand exchange at the edge aluminol sites is the most probable explanation for the uptake of the negatively charged organic test compounds by the clay surface. The breakthrough behaviour of organic anions was additionally impacted by anion exclusion in illite. The demonstrated weak retardation of the test compounds can be robustly introduced in transport models, leading thus to a much lower contribution of 14 C to the expected long-term overall dose. [ABSTRACT FROM AUTHOR]

Efficient removal of hexavalent chromium Cr(VI) is a stringent issue which requires efficient and, preferable, reusable sorbents. In this context, novel composite sorbents were designed in this work consisting of a combination between the chitosan (CS) and a synthetic polycation, poly(vinyl amine) (PVAm), in a ratio of 80:20, w/w, dual-cross-linked with glutaraldehyde (GA) and ethylene glycol diglycidyl ether (EGDGE), in which the microspheres of some porous strong base anion exchangers (IEx) having (vinylbenzyl diethyl 2-hydroxyethyl)ammonium chloride functional groups, and sizes in the range 90–200 μm, were evenly dispersed. Macroporous CS/PVAm/IEx composites as cryobeads or monoliths were applied to the sorption of Cr(VI) from synthetic aqueous solutions, in batch mode. The results revealed that the sorption of Cr(VI) oxyanions was high in the range of pH 3–6, and abruptly decreased when pH was >6. The pseudo-first order kinetic equation well fitted the kinetics profiles obtained with all composites indicating that electrostatic interaction dominated the sorption process. Equilibrium sorption results of Cr(VI) onto composite cryobeads were the best described by the Sips, Langmuir, and Temkin isotherm models. The maximum sorption capacity evaluated by the Langmuir model at 25 °C was in the range 200–320 mg Cr(VI)/g adsorbent. The sorption process proved to be spontaneous and endothermic. The composite cryogels could be repeatedly used in the sorption of Cr(VI), a low decrease of the adsorption capacity being observed after five consecutive sorption/desorption cycles. The remarkable sorption capacities, and high reusability of the CS/PVAm/IEx composites suggest the promising potential of these novel sorbents in the removal of Cr(VI). [ABSTRACT FROM AUTHOR]

This paper reports the systematic performance evaluation and mechanism elucidation of a multi-layered graphene oxide (GO) membrane in removing ionic and organic species from water at different pH levels. The rejections of representative monovalent (Na + , Cl - ) and multivalent ions (SO 4 2- , Mg 2+ ) as well as organic dyes (methylene blue, rhodamine-WT) and pharmaceutical and personal care products (triclosan, triclocarban) by the GO membrane were tested in a reverse osmosis membrane system. It was found that, at pH 7, the GO membrane exhibited high removal of multivalent cations/anions and all tested organics, regardless of their charges, sizes, or hydrophobic properties, but low removal of monovalent ions. Such removal behavior is dramatically different from that of traditional nanofiltration membranes, which are often negatively charged and can only remove multivalent ions and organics that also bear negative charges. As pH varied, the key properties (e.g., charge, interlayer spacing) of the GO membrane were significantly changed, leading to different pH-dependent interfacial phenomena and separation mechanisms, and demonstrating the promise of using the GO membrane as a pH-responsive membrane. It was also revealed that the molecular shape of some organics (e.g., triclocarban) greatly affected their removal due to the mobility and thus π-π interaction of such organics with the carbon surface of the GO membrane. Finally, implications for the future development of high-performance GO membranes are discussed. [ABSTRACT FROM AUTHOR]

The superionic state of crystals with the fluorite structure caused by disordering of anion sublattice is accompanied by the formation of short-lived clusters due to the correlation between anti-Frenkel defects at the increase of their concentration. The existence of clusters comprising anion vacancies as well as interstitial and displaced anions at high temperatures was deduced from the analysis of neutron scattering. The quenched CaF 2 crystals show intense ultraviolet absorption with a long-wavelength tail that can be ascribed to the clusters thus testifying the opportunity of a high-temperature disorder freezing. It was found that the fluorine vacancies introduced into the crystal during preheating in the reduction atmosphere of calcium vapor trigger and intensify the process of cluster formation. The model that takes into account a strong electron-vibration coupling gives rise to the reconstruction of both the valence and conduction bands in the cluster region thereby clarifying the nature of absorption spectra of quenched crystals. [ABSTRACT FROM AUTHOR]

Membrane bioreactors are effective and attractive for wastewater reclamation and reuse, but phosphorus polishing is required to meet more stringent environmental regulations. Mixed metal oxide coated beads composed of Fe-Ti bimetal oxides on a sulfonated polymer were fabricated, characterized, and tested for phosphorus removal from membrane bioreactor effluents. Ti doping substantially enhanced the adsorption rate and capacity of the coated beads, possibly due to more positively charged surfaces. The mixed metal oxide coated beads were highly selective to phosphate ions (selectivity factor >25) against background ions (e.g., Cl − , NO 3 − , and SO 4 2− ), although they were less selective against bicarbonate and organics. Regenerated beads showed greater adsorption performance than the virgin ones. Ca binding to mixed metal oxide layers was responsible for enhanced phosphorus sorption, presumably resulting from the formation of calcium phosphate. The phosphorus recovery from the exhausted column adsorber was successful with alkaline solution (e.g., >90% P was recovered at a NaOH load of 0.2 eq/L bed. Using mixed metal oxide chemically anchored on polymer beads for phosphorus sorption would be a promising complement to biological phosphorus removal. [ABSTRACT FROM AUTHOR]

The retention behavior of inorganic anions was investigated on a hydrophobic stationary phase dynamically modified with 18-crown-6 ether (18C6) in capillary ion chromatography. Styrene-divinylbenzene copolymeric (polystyrene) packing material was used as the hydrophobic stationary phase to retain 18C6. The eluent contained 18C6, salt and acetonitrile; 18C6 was retained on the stationary phase and the analytes anions were separated by the cations, which were trapped on the 18C6 and worked as the anion-exchange sites. The effect of eluent conditions, such as eluent cation species, acetonitrile (ACN), 18C6, and salt concentrations (in this case, potassium chloride was used), was investigated. The retention times of inorganic anions decreased with increasing concentration of ACN. In case ACN concentration was less than 4%, the retention times decreased with the passage of time. The retention time of inorganic anions increased with increasing concentrations of 18C6 and potassium chloride concentrations. By contrast, high concentration of 18C6 and chloride in eluent promotes elution of inorganic anions, and the retention time decreased. Furthermore, a contactless conductivity detector was used to replace the conventional UV detector to obtain higher sensitivity detection. Separation of inorganic anions was achieved with the eluent containing potassium hydroxide and enhanced peak intensity was observed using a suppressed contactless conductivity detection. Graphical abstract: [ABSTRACT FROM AUTHOR]

The competition of intense-field multiple-detachment with efficient photodissociation of F2 is studied as a function of laser peak intensity. The main product channels are disentangled and characterized by 3D coincidence fragment imaging. The presented kinetic energy release spectra, angular distributions, as well as two-color pump-probe measurements allow identification of competing sequential and nonsequential mechanisms. Dissociative detachment, producing two neutral atoms (F + F), is found to be dominated by a sequential mechanism of photodissociation (F + F), followed by detachment of the atomic anion fragment. In contrast, dissociative ionization (F + F+) shows competing contributions of both a sequential two-step mechanism as well as a nonsequential double-detachment of the molecular anion, which are distinguished by the kinetic energy released in the dissociation. Triple-detachment is found to be nonsequential in nature and results in Coulomb explosion (F+ + F+). Furthermore, the measured kinetic energy release for dissociation on the ²Σg+ state provides a direct measurement of the F2 dissociation energy, D0 = 1.26 ± 0.03 eV. [ABSTRACT FROM AUTHOR]

Atom transfer radical polymerization (ATRP) of a viologen-containing methacrylate, 1-propyl-1'-[2-(methacryloyloxy) ethyl]-4,4'-bipyridinium dihexafluorophosphate, is reported. To achieve good polymerization control, it was essential to use the viologen-based monomer with a hexafluorophosphate instead of halide counterion, and 2,2'-bipyridine as the ligand for the Cu-based ATRP catalyst. The solubility of produced cationic polymers could be tuned by anion metathesis: the polymers with hexafluorophosphate counterions were soluble in organic solvents (e.g., acetone, DMF), and those with chloride counterions were water-soluble. In aqueous solutions, the polymers (chloride salts) formed large aggregates, the sizes of which ranged from about 200 to about 400 nm (based on dynamic light scattering measurements) depending on the molecular weight. Upon addition of electrolytes (e.g., NaCl), the aggregates underwent dissociation. The apparent diffusion coefficients of the aggregates existing in aqueous solutions and the products of their electrolyte-induced dissociation were measured by diffusion-ordered NMR spectroscopy. The association--dissociation processes were also studied by fluorescence spectroscopy: the aqueous polymer solutions, which were originally fluorescent (λem = 402 nm at λex = 350 nm), lost their fluorescence in the presence of NaCl. The addition of small amounts the viologen-containing polyelectrolytes to solutions of inorganic salts (NaCl) altered the crystal morphology of the salts due interaction of the multiple charged pendant groups with small ions. In the presence of reducing agents, the pendant viologen groups were converted to viologen radical-cations, which are prone to dimerize reversibly in aqueous solutions. Indeed, marked dimerization of viologen radical cations (with absorbance maxima at 520 and 870 nm) was observed in relatively dilute aqueous solutions (4 mg mL-1) upon addition of reducing agents (hydrazine). [ABSTRACT FROM AUTHOR]

A portable capillary electrophoresis instrument with dual capacitively coupled contactless conductivity detection (C4D) was used to determine the inorganic ionic profiles of three pharmaceutical samples and precursors of two illicit drugs (contemporary samples of methylone and para‐methoxymethamphetamine). The LODs ranged from 0.10 μmol/L to 1.25 μmol/L for the 10 selected cations, and from 0.13 μmol/L to 1.03 μmol/L for the eight selected anions. All separations were performed in less than 6 min with migration times and peak area RSD values ranging from 2 to 7%. The results demonstrate the potential of the analysis of inorganic ionic species to aid in the identification and/or differentiation of unknown tablets, and real samples found in illicit drug manufacture scenarios. From the resulting ionic fingerprint, the unknown tablets and samples can be further classified. [ABSTRACT FROM AUTHOR]

An analytical procedure consisting of high pressure/temperature acid digestion using an UltraCLAVE system and a one pass, single column matrix separation using DOWEX AG 1X8 anion exchange resin was applied to the determination of Cr concentrations and δ53Cr in chromites, soils, and biological matrices (epiphytic lichens and mosses) using a combination of ICP-SFMS and MC-ICP-MS. The overall reproducibility of the method was assessed by replicate preparation and Cr isotope ratio measurements performed by different operators in multiple analytical sessions over a few months and was found to be 0.11‰ (2σ). The accuracy was evaluated using commercially available reference materials for which measured data were compared with certified values (for Cr concentrations) and previously published results (for isotope data). The results demonstrate a uniform Cr isotope composition in soil depth profiles sampled in different urban environments. A strong negative correlation between δ53Cr and Cr concentrations in lichens and mosses indicates that airborne Cr from local anthropogenic source(s) is depleted in heavy isotopes. [ABSTRACT FROM AUTHOR]

Chiral, neutral H-bond donors have found widespread use as catalysts in enantioselective reactions involving ion-pair intermediates. Herein, a systematic mechanistic study of a prototypical anion-binding reaction, the thiourea-catalyzed enantioselective alkylation of α-chloroethers, is detailed. This study reveals that the catalyst resting state is an inactive dimeric aggregate that must dissociate and then reassemble to form a 2:1 catalyst-substrate complex in the rate-determining transition structure. Insight into this mode of catalyst cooperativity sheds light on the practical limitations that have plagued many of the H-bond donor-catalyzed reactions developed to date and suggests design strategies for new, highly efficient catalyst structures. [ABSTRACT FROM AUTHOR]

Cationic frameworks can selectively trap anions through ion exchange, and have applications in ion chromatography and drug delivery. However, cationic frameworks are much rarer than anionic or neutral ones. Herein, we propose a concept, preemptive coordination (PC), for targeting positively charged metal-organic frameworks (P-MOFs). PC refers to proactive blocking of metal coordination sites to preclude their occupation by neutralizing ligands such as OH−. We use 20 MOFs to show that this PC concept is an effective approach for developing P-MOFs whose high stability, porosity, and anion-exchange capability allow immobilization of anionic nucleotides and coenzymes, in addition to charge- and size-selective capture or separation of organic dyes. The CO2 and C2H2 uptake capacity of 117.9 cm3 g−1 and 148.5 cm3 g−1, respectively, at 273 K and 1 atm, is exceptionally high among cationic framework materials. [ABSTRACT FROM AUTHOR]

It had been reported that alumina nanoshell coating could be obtained on the external surface of various substrates in one-nanometer precision in aqueous solution. In this work, alumina nanoshell coated mesoporous silica microbeads (nanoAl 2 O 3 /mesoSiO 2 ) were prepared with the similar method, and were successfully applied to inorganic anions separation. As the mass transfer speed is largely constrained in the mesopore compared with that on the open surface, it was found that a complete alumina nanoshell coating could be obtained within the mesopore until the five-time coating was carried out. After characterization by BET, SEM and FTIR, it was found that the obtained nanoAl 2 O 3 /mesoSiO 2 particles are smooth and well dispersed, and the mesopores are well reserved. In addition, the full coverage of nanoAl 2 O 3 shell in mesopores was also confirmed by the binding capacity experiments with berberine. Finally, the nanoAl 2 O 3 /mesoSiO 2 particles were packed in silica capillary for the separation of inorganic anions I − , SCN − , Br − , NO 2 − and NO 3 − with ion chromatography (IC), and a column efficiency of 3.8 × 10 4 plates per meter was obtained for I − . [ABSTRACT FROM AUTHOR]

The objective of this study was to identify the removal mechanisms of radionuclides by reverse osmosis (RO) membranes under conditions relevant to full-scale water treatment. For this purpose, the effects of feed solution chemistry on the removal of Cs and Sr by a low pressure RO system was investigated by systematically varying membrane surface charge, ionic composition, and organic matter concentrations. The results showed that the effects of solution chemistry on the filtration of Cs and Sr were related to their hydrated ionic radius, resulting in the predominance of the Donnan’s effect and electrostatic interactions, respectively. Consequently, the rejection of Cs increased more pronouncedly than Sr with the increases of feed concentration. Due to the Donnan’s effect, different anions decreased the rejection of Cs to different extents in accordance to the order of anions’ radii as SO 4 2− > Cl − > NO 3 − > F − . The variations in Sr rejection were influenced by the electrostatic interactions between Sr 2+ and the membrane. In addition, humic acid (HA) lowered the rejection of Cs and caused significant membrane flux decline, but did not change the rejection of Sr. Sr also aggravated HA fouling of the membrane. [ABSTRACT FROM AUTHOR]

The article focuses on applications of supramolecular anion recognition. Topics include discrete colorimetric and fluorescence (Optical) anion sensors; extraction methods such as liquid-liquid extraction and solid-liquid extraction for separation of anions; and organocatalysis based on interactions with halide anions.

Interface-free two-dimensional heart-cutting capillary electrophoresis for two different classes of analytes (anionic and neutral) in a single capillary is presented. Simultaneous sample stacking and orthogonal separation were demonstrated. The anionic species were first analyzed by capillary zone electrophoresis in the first dimension. Then, the neutral compounds were separated in the second dimension by micellar electrokinetic chromatography using the common anionic surfactant sodium dodecyl sulfate. The first and second dimensions occurred automatically without changing the electrolyte and without polarity switching. Artificial mixtures (five anions and four neutral compounds) were successfully analyzed with sensitivity enhancement factors from 7 to 28. The orthogonal separation was complete within 8 min. Some analytical features and application to a spiked real river water sample were also studied. [ABSTRACT FROM AUTHOR]

Cetyltrimethylammonium bromide (CTAB) capped 9-Anthraldehyde nanoparticles (9-AANPs) in aqueous suspension prepared by reprecipitation method are seen brick shaped in Scanning Electron Microscope image. The Dynamic Light Scattering histogram of nanoparticle suspension reveals narrow particle size distribution and average particle size is 89 nm. The positive zeta potential 20.8 mV measured on zeta sizer indicates high level stability of nanoparticle suspension. The blue shift of 65359.47 cm observed in the UV-Visible absorption spectrum of CTAB capped 9-AANPs from the absorption maximum of dilute solution of 9-Anthraldehyde (9-AA) in acetone is an indication of formation of H-bonded aggregates by π stacking effect. The strong Aggregation Induced Enhanced Emission (AIEE) of CTAB capped 9-AANPs at 537 nm is selectively quenched with addition of phosphate anion solution. The fluorescence quenching results of the nanoparticle in aqueous solution fit into conventional Stern-Volmer relation in the range of phosphate ion concentration of 0-40 μM. The possible mechanism of fluorescence quenching of nanoparticle is explained by considering adsorption of phosphate anion electrostatistically on positively charged surface of nanoparticle generated by CTAB cap. The Langmuir adsorption plot constructed for PO adsorption on the basis of fluorescence quenching results of CTAB capped 9-AANPs is linear. The estimated value of Langmuir constant (K) and Stern - Volmer constant (K) are in close agreement within experimental limits. The sensing method of phosphate ion based on fluorescence quenching of 9-AANPs is applied successfully for quantification of phosphate from pharmaceutical tablet chloroquine phosphate and hence to determine the amount of chloroquine. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Transport of two principal inorganic iodine anions separately in two crushed crystalline granitic rocks, gabbro and tonalite, have been investigated. The rocks were crushed and sieved, and finally a fraction between 0.25 and 0.80 mm was filled in 5 cm PET columns (medical syringes) of 5.40 cm length and 1.24 cm in inner diameter. NaI and NaIO were dissolved in synthetic groundwater (SGW) in a concentration as low as 10 mol/dm. The SGW was pumped into the columns at a seepage velocity of 0.031 ± 0.001 cm/min using a multi-head peristaltic pump. Iodine concentration in the outflow SGW from the columns was determined by UV-Vis spectrophotometry at 510 nm absorption maximum in CHCl using redox reactions. By the use of a dependence of concentration on the number of pore volumes from the outflow and the linear isotherm model, based on erfc-function, breakthrough curves were constructed and the principal transport parameters were calculated. The values of sorption and desorption retardation coefficients of about 1 for both iodide and iodate have been obtained, which show evidence of practically non-sorption behavior of these chemical forms of iodine in the tested granitic rocks. The values of hydrodynamic dispersion coefficients and corresponding Peclet numbers were about 0.0077 ± 0.0006 and 21.6 ± 1.8 cm/min, respectively, for both anions and rocks under given conditions. [ABSTRACT FROM AUTHOR]

This Feature Article covers recent developments in anion induced capsular self-assemblies, with particular focus on important reports from 2011 to 2013. Contemporary studies on the capsular binding of environmentally and biologically relevant anions in aqueous medium are described. Emerging reports of such systems reveal their potential utility towards various functional aspects like anion separation, CO2 fixation, hydrated halide recognition and anion transportation. This article also highlights potential applications of anion induced molecular capsules. [ABSTRACT FROM AUTHOR]

The present article deals with a newer class of ligand bridged asymmetric complexes incorporating ancillary ligands (AL) with varying electronic characteristics: [(bpy)2RuII(μ-HL2−) RuII(bpy)2](ClO4)2·([1](ClO4)2); [(pap)2RuII(μ-HL2−)RuII(pap)2](ClO4)2 ([2](ClO4)2); [(bpy)2RuII(μ-HL2−)RuII(pap)2](ClO4)2 ([3](ClO4)2); [(acac)2RuIII(μ-HL2−)RuIII(acac)2] (4) and [(bpy)2RuII(μ-HL2−)RuIII(acac)2]ClO4 ([5]ClO4) (H3L: 5-(1H-benzo[d]imidazol-2-yl)-1H-imidazole-4-carboxylic acid, bpy = moderately π-accepting 2,2′-bipyridine, pap = strongly π-accepting 2-phenylazopyridine, acac− = σ-donating acetylacetonate). The molecular identity of [1](ClO4)2 was established by its single crystal X-ray structure. A large shift in Ru(ii)/Ru(iii) potential of 0.7–2.0 V took place on switching the ancillary ligands from AL = bpy to pap to acac−, leading to the stabilisation of ruthenium(ii) and ruthenium(iii) states in 12+, 22+, 32+, 4 and 5+, respectively. The detailed magnetic studies revealed that the paramagnetic RuIIIRuIII state in 4 essentially behaves as a system with two independent S = 1/2 spins and it exhibits an anisotropic EPR at 77 K (＜g＞ = 2.192, Δg = g1−g3 = 0.70) but without any half-field signal near g∼ 4. The isolated mixed valent RuIIRuIII state in 5+ exhibits weak antiferromagnetic coupling of −0.25 cm−1 and anisotropic EPR with ＜g＞ = 2.155, Δg = 0.704 but fails to show a RuII→ RuIII IVCT (intervalence charge transfer) transition in the near-IR region up to 2000 nm. The complexes 12+, 22+ and 4 encompassing identical metal fragments, exhibited weak to moderate electrochemical coupling at the intermediate mixed valent states with Kc values of 102–105. The coulometrically generated mixed valent RuIIRuIII state in 13+ or 4− also failed to display any prominent absorption in the near-IR region, but exhibited RuIII based rhombic EPR, implying valence localised situation with negligible intermetallic electronic coupling. The complexes 22+, 32+, 4 and 5+ having one NH proton associated with the bridging ligand HL2− do not show any interaction with the anions F−, Cl−, Br−, I−, HSO4−, H2PO4−, OAc− and SCN− in CH3CN, though 12+ selectively recognises the fluoride ion. [ABSTRACT FROM AUTHOR]

Conditions for the quantitative separation of rhenium and selenium using anionites with isoporous structures are investigated with regard to the washing acid of the Balkhashskii Copper-Smelting Plant of KAZAKHMYS Corporation, which allows for the development of a unified technology for processing mixed rhenium-selenium solutions and obtaining end products, namely, high-clean ammonium perrhenate and elementary selenium. The completeness of metal separation is due to the development of methods for removing selenium both at the step of rhenium sorption and at the step of picking dynamic processes of impurities from the resin phase before rhenium desorption. Processes for the frontal-gradient removal of selenium from Purolite A170 weakly alkaline anionite have been developed, as well as marks of ionites for selective selenium sorption in order to obtain an associated product along with ammonium perrhenate. [ABSTRACT FROM AUTHOR]

Atom transfer radical addition (ATRA) and polymerisation (ATRP) reactions are commonly catalyzed by copper(i) complexes which react, reversibly, with a dormant alkyl halide initiator (RX) releasing a reactive organic radical RṖ. The copper catalyst bears a multidentate N-donor ligand (L) and the active catalyst is simply CuIL. The role of the catalyst in these reactions is to abstract a halogen atom from RX forming the corresponding higher oxidation state species CuIILX. However, in order to perform its catalytic function (in multiple turnovers) the halido ligand must be released from the copper ion en route to regenerating the active catalyst CuIL. In this work we investigate the kinetics of the CuILX/CuIL equilibrium where L is the tridentate N,N,N′,N′′,N′′-pentamethyl-diethylenetriamine (PMDETA). Using electrochemical analysis we find that the rate of formation of the active catalyst CuIL is strongly dependent on solvent. We demonstrate that both the kinetics and thermodynamics of this simple ligand exchange reaction are critical in the overall reaction pathway. [ABSTRACT FROM AUTHOR]

The reactions of NOyspecies in theatmosphere with sea spray aerosol replace halogen anions with nitrate.These experiments show the effect of increasing the nitrate contentof model sea spray aerosol particles on the morphology changes andthe phase transitions driven by changes in relative humidity (RH).The components of the model particles include H2O, Na+, Mg2+, Cl–, NO3–, and SO42–. Tandem differentialmobility analyzer (TDMA) measurements yield the water content andefflorescence relative humidity (ERH) of these particles, and probemolecule spectroscopic measurements reveal subsequent phase transitionsand partially characterize the salt composition on the surface ofdry particles. The results show three effects of increasing the nitratecomposition: decreasing the EFH (46 to 29%), production of a metastableaqueous layer on the surface of effloresced particles, and decreasingthe sulfate content near the surface of dry particles. For the mixturesstudied here, the initial crystallization event forms a core of NaCl.For particles that contain a substantial metastable aqueous layerfollowing efflorescence, probe molecule spectroscopy shows a secondcrystallization at a lower RH. This subsequent phase transition islikely the formation of Na2SO4. Homogeneousnucleation theory (HNT) using a semiempirical formulation predictsthe ERH of all mixtures within 2.0% RH, with a mean absolute deviationof 1.0%. The calculations suggest that structures associated withhighly concentrated or supersaturated magnesium ions strongly affectthe interfacial tension between the NaCl crystal nucleus and the dropletfrom which it forms. [ABSTRACT FROM AUTHOR]

The separation performance of inorganic anions ReO4−, Br−, SO42−, and NO3− using porphyrin–alkaloid quaternary salt transporters is examined using parallel artificial membrane permeability assay. Active and selective transport of perrhenate is achieved by porphyrin–brucine conjugates. Herein, chlorides are used as antiporters and complete removal of perrhenates from a source solution is stimulated due to electrostatic effects. [ABSTRACT FROM AUTHOR]

A series of Cd(ll) coordination frameworks that are constructed from a new oxadiazole-bridged ligand 3,5-bis(3-pyridyl-3-(3'-methylphenyl)-1,3,4-oxadiazole (L) and CdX2 (X = N03", Cl-, Br-, 1", N3", and SCN-) were synthesized. The N03- anion of the solid CdL2(NO3)22THF (l) is able to be quantitatively exchanged with Cl-, Br", T, SCN-, and N3~ in the solid state. For Cl- and Br-, the anion exchange resulted in a anion-induced structural transformation to form the structures of 2 and 3, respectively. In addition, the Cd(ll) structure herein exhibits the anion-responsive photoluminescence, which could be a useful method to monitor the anion-exchange process. Notably, compound 1 can recognize and completely separate SCN-/N3" with similar geometry.

Abstract: We describe the ion chromatographic separation of inorganic anions using a diol-stationary phase column (–CH(OH)CH2OH; diol-column) without charged functional groups. Anions were separated using acidic eluent as in typical anion-exchange chromatography. The retention volumes of anions on the diol-column increased with increasing H+ concentration in the eluent. The anion-exchange capacities of diol-columns in the acidic eluent (pH 2.8) were larger than that of zwitterionic stationary phase column but smaller than that of an anion-exchange column. The separation of anions using the diol-column was strongly affected by the interaction of H+ ions with the diol-functional groups and by the types of the eluents. In particular, the selection of the eluent was very important for controlling the retention time and resolution. Good separation was obtained using a diol-column (HILIC-10) with 5mM phthalic acid as eluent. The limits of detection at a signal-to-noise ratio of 3 ranged from 1.2 to 2.7μM with relative standard deviations (RSD, n =5) of 0.04–0.07% for the retention time and 0.4–2.0% for the peak areas. This method was successfully applied to the determination of H2PO4 −, Cl−, and NO3 − in a liquid fertilizer sample. [Copyright &y& Elsevier]