Cation Columns Research Articles

Synthesis and structural characterization of polyiodides of rare-earth urea complexes: crystal structures of [Ho(Ur)7][I3]3 and [Pr(Ur)8][I5][I3]2[I2

Reactions of LnI3·nH2O, I2, and urea (Ur) produced rare-earth polyiodides [Ln(Ur)8][I5][I3]2[I2] (Ln = Pr, Nd, Sm–Tb) and [Ln(Ur)7][I3]3 (Ln = Ho, Er); the crystal structures of the praseodymium and holmium compounds were solved. In [Ho(Ur)7][I3]3, holmium ions are located at the centers of distorted pentagonal bipyramids (three independent complex cations) and an octahedra with a split vertex (one independent cation) of oxygens of coordinated urea. All triiodide anions are symmetric and linear; they are united in almost linear infinite chains by short contacts. The almost parallel chains of iodine atoms form infinite walls of honeycomb-like channels, and the columns of the complex cations are localized in these channels. Complex [Pr(Ur)8][I5][I3]2[I2] is isotructural to the earlier reported [Dy(Ur)8][I5][I3]2[I2].

Evaluation of Flotation Collectors in Developing Zero Waste Technology for Processing Iron Ore Tailings

Reverse cationic column flotation technology is gaining traction in iron ore processing industry for recovering iron values from iron ore slimes/tailings. Development and selection of appropriate collector suitable to the material to be processed plays vital role in the development of the process/technology. Three cationic collectors which are vegetable oil based, biodegradable and environmental friendly were tested for their efficacy in reducing alumina and silica and improve iron content in the tailings of an operating iron ore washing plant. Selectivity index as defined by Douglas was used as response parameter to measure the efficiency of separation while comparing the performance of these collectors during flotation tests. Sokem 522C proved to be better in comparison to Sokem 701 and Sokem 702 with the highest selectivity index of 20.87. The concentrate generated analyzed 63.30% Fe, 2.20% SiO2 and 2.52% Al2O3 with 69.00% weight recovery and 79.21% Fe recovery from the tailings containing 55.14% Fe, 17.34% SiO2 and 4.04% Al2O3. The concentrate generated is suitable for pellet making due to its attractive granulometry and acceptable levels of alumina content (≤ 2.50%) in it. The tailings generated in this process could be utilised for cement manufacturing and tiles or pavement blocks making.The process developed is ‘zero waste’ while mitigating the environmental issues related to managing tailings in iron ore processing plants.

Purification and characterization of saxitoxin from Mytilus chilensis of southern Chile

In the current communication we describe an innovative method to purify saxitoxin (STX), a toxin presents in contaminated muscle of Mylitus chilensis extracted in the southern part of Chile, using a liquid chromatographic methodology based on ionic pairs. The STX was extracted using HCl and treated with ammonium sulfate following a treatment with trichloroacetic acid and hexane/diethyl ether (97/3). The samples were analyzed by a semi-preparative HPLC in order to collect pure fractions of STX and these fractions were eluted in solid-phase cationic interchange SCX extraction columns. The purified STX was stable and homogeneous and its identity was confirmed by LC–MS–MS, which demonstrated a high quality purification of STX, without presence of analogs such as neosaxitoxin (Neo) and decarbamoyl saxitoxin (dcSTX). The STX biological activity was analyzed in a bioassay in mice model and compared to the standard STX produced by the FDA and no significant differences were observed.

Determination of Platinum‐Group Elements in Geological Samples by Isotope Dilution‐Inductively Coupled Plasma‐Mass Spectrometry Combined with Sulfide Fire Assay Preconcentration

A method was developed for the determination of platinum‐group elements (PGE) in geological samples by isotope dilution‐inductively coupled plasma‐mass spectrometry combined with sulfide fire assay preconcentration. Samples were fused and PGE analytes were concentrated in sulfide buttons. The buttons were dissolved using HCl leaving PGE analytes in insoluble residues, which were digested in HNO3 and simultaneously processed for the distillation of Os. The remaining solutions were further prepared for the purification of Ru, Rh, Pd, Ir and Pt using a tandem assembly of cation and Ln resin columns. The eluents were directly analysed by membrane desolvation‐ICP‐MS. Ruthenium, Pd, Os, Ir and Pt were determined by isotope dilution, whereas Rh was determined by conventional reference material calibration combined with 193Ir as the internal standard element. The method was validated using a series of PGE reference materials, and the measurement data were consistent with the recommended and the literature values. The measurement precision was better than 10% RSD. The procedural blanks were 0.121 ng for Ru, 0.204 for Rh, 0.960 ng for Pd, 0.111 ng for Os, 0.045 ng for Ir and 0.661 ng for Pt, and the limits of detection (3s) were 0.011 ng g−1 for Ru, 0.008 ng g−1 for Rh, 0.045 ng g−1 for Pd, 0.009 ng g−1 for Os, 0.006 ng g−1 for Ir and 0.016 ng g−1 for Pt when a test portion mass of 10 g was used. This indicates that the proposed method can be used for the determination of trace amounts of PGE in geological samples.

Crystal structure of tetra-methyl-tetra-thia-fulvalenium (1S)-camphor-10-sulfonate dihydrate.

Electro-oxidation of tetra-methyl-tetra-thia-fulvalene (TMTTF) in the presence of the chiral anion (1S)-camphor-10-sulfonate (S-camphSO3 (-)) in tetra-hydro-furan/water medium afforded a 1/1 salt formulated as TMTTF·S-camphSO3·2H2O or 2-(4,5-dimethyl-1,3-di-thiol-2-yl-idene)-4,5-dimethyl-1,3-di-thiole radical ion (1+) [(1S)-7,7-dimethyl-2-oxobi-cyclo-[2.2.1]heptan-1-yl]methane-sulfonate dihydrate, C10H12S4 (+)·C10H15O4S(-)·2H2O. In this salt, two independent TMTTF units are present but, in both cases, the observed bond lengths and especially the central C=C distance [1.392 (6) and 1.378 (6) Å] are in agreement with a complete oxidation of TMTTF which is thus present as TMTTF (.) (+) radical cations. These cations form one-dimensional stacks in which they are associated two by two, forming dimers with short [3.472 (1) to 3.554 (2) Å] S⋯S contacts. The two S-camphSO3 anions present also form stacks and are connected with each other via the water mol-ecules with many O-H⋯O hydrogen bonds ranging from 1.86 (3) to 2.15 (4) Å; the O-H⋯O hydrogen-bonding network can be described as being constituted of C 2 (2)(6) chains bearing R 3 (3)(11) lateral rings. On the other hand, the columns of cations and anions are connected through C-H⋯O hydrogen bonds, forming a system expanding in three directions; finally, the result is a three-dimensional network of O-H⋯O and C-H⋯O hydrogen bonds.

Rapid quantification of imidazolium-based ionic liquids by hydrophilic interaction liquid chromatography: Methodology and an investigation of the retention mechanisms

The separation of nine N,N′-dialkylimidazolium-based ionic liquids (ILs) by an isocratic hydrophilic interaction high-performance liquid chromatographic method using an unmodified silica column was investigated. The chosen analytical conditions using a 90:10 acetonitrile–ammonium formate buffer mobile phase on a high-purity, unmodified silica column were found to be efficient, robust, and sensitive for the determination of ILs in a variety of solutions. The retention window (k′=2–11) was narrower than that of previous methods, resulting in a 7-min runtime for the nine IL homologues. The lower limit of quantification of the method, 2–3μmolL−1, was significantly lower than those reported previously for HPLC-UV methods. The effects of systematically modifying the IL cation alkyl chain length, column temperature, and mobile-phase water and buffer content on solute retention were examined. Cation exchange was identified as the dominant retention mechanism for most of the solutes, with a distinct (single methylene group) transition to a dominant partitioning mode at the highest solute polarity.

Direct imaging of octahedral distortion in a complex molybdenum vanadium mixed oxide.

Complex Mo,V-based mixed oxides that crystallize in the orthorhombic M1-type structure are promising candidates for the selective oxidation of small alkanes. The oxygen sublattice of such a complex oxide has been studied by annular bright field scanning transmission electron microscopy. The recorded micrographs directly display the local distortion in the metal oxygen octahedra. From the degree of distortion we are able to draw conclusions on the distribution of oxidation states in the cation columns at different sites. The results are supported by X-ray diffraction and electron paramagnetic resonance measurements that provide integral details about the crystal structure and spin coupling, respectively.

Direct Imaging of Octahedral Distortion in a Complex Molybdenum Vanadium Mixed Oxide

AbstractComplex Mo,V‐based mixed oxides that crystallize in the orthorhombic M1‐type structure are promising candidates for the selective oxidation of small alkanes. The oxygen sublattice of such a complex oxide has been studied by annular bright field scanning transmission electron microscopy. The recorded micrographs directly display the local distortion in the metal oxygen octahedra. From the degree of distortion we are able to draw conclusions on the distribution of oxidation states in the cation columns at different sites. The results are supported by X‐ray diffraction and electron paramagnetic resonance measurements that provide integral details about the crystal structure and spin coupling, respectively.

Second‐Sphere Complexation of Thorium(IV) by Cucurbit[6]uril with Included Perrhenate Counterions – Crystal Structure and Hirshfeld Surface Analysis

AbstractThe reaction of thorium(IV) nitrate with cucurbit[6]uril (CB6) in the presence of perrhenic acid in water gives the complex [Th(NO3)(H2O)8][(ReO4)(CB6)](ReO4)2·3H2O (1). Aquated cations are held at both CB6 portals by ion–dipole and hydrogen‐bonding interactions, and one of the ReO4– anions is included in the CB6 cavity. The packing displays columns of alternate cations and encapsulated anions. Hirshfeld surfaces are used to visualize short contacts between the species present.

On the Origin of Nanochessboard Superlattices in A-Site-Deficient Ca-Stabilized Nd2/3TiO3

A-site deficient Nd2/3TiO3 ceramics stabilized with CaTiO3, with an overall composition of 0.9 Nd2/3TiO3–0.1 CaTiO3, were synthesized by the mixed oxide route. Synchrotron X-ray diffraction was used to identify the basic perovskite structure and revealed cross-type superlattice reflections. An incommensurate superlattice structure with dimensions of a ≈ b ≈ 20ap and c = 2ap (where ap is the cell parameter for the parent perovskite phase) was identified, giving rise to contrast features resembling a nanochessboard pattern in electron microscopy images. The superlattice was further characterized by aberration-corrected scanning transmission electron microscopy (STEM): atomically resolved lattice images were obtained along ⟨100⟩ orientations to visualize the A-site (Ca, Nd, and vacancies) and B-site (Ti) cation column intensities, in correlation with observations of the nanochessboard superlattice. Electron energy loss spectroscopy (EELS) was used to precisely determine the distribution of Nd and Ca across t...

Functional properties ensue from cooperation of different interactions

According to the definition recommended by IUPAC [1], a halogen bond (XB) occurs when there is evidence of a net attractive interaction between an electrophilic region in a halogen atom and a nucleophilic region in another atom. The halogen bond has many similarities with the hydrogen bond (HB) and here we discuss the specific profile of the two interactions. We also show how the cooperation between the two interactions afford crystalline systems possessing unique and useful properties. For instance, the diiodide, dibromide, and dichloride salts of the 1,6-bis(trimethylammonium)hexane cation (hexamethonium, HMET2+, cation) react with two equivalents of diiodine in a solid-gas reaction and the corresponding bis-trihalides (halogen bonded adducts) are formed [2]. No cavities are present in the starting dihalides and the observed behavior reveals the dynamically porous character of bis(trimethylammonium)alkane dihalides. In the obtained bis-trihalides a net of X-···H-C HBs (X=Cl, Br, I) plays a decisive role in controlling the crystal packing: Four cationic columns embrace an anionic twin column formed by stacking of trihalide dimers. When heated, these bis-trihalides lose one diiodine molecule and the virtually unknown tetrahalide dianions [I4]2-, [I2Br2] 2-, and [I2Cl2]2-are formed. These dianions are the product of the double pinning of a diiodine molecule by two halide anions via strong XBs. The last two tetrahalides were never obtained in solution. The confined environment of dynamically porous materials clearly confers useful synthetic opportunities relative to solution-state processes. Other cases are described wherein XB and HB cooperate in driving self-assembly processes which afford solid materials endowed with useful properties. For instance, we will discuss the formation of two-component supramolecular gels [3] wherein a bis-urea and a diiodoarene self-assemble via cooperative XB and HB.

Synthesis and structural characterization of a cocrystal salt containing acriflavine and 3,5-dinitrobenzoic acid

An acriflavine cocrystal salt with 3,5-dinitrobenzoic acid (stoichiometry 1:3) was synthesized and structurally characterized. This is the first crystal structure containing the acriflavine moiety to be documented and also the first in which a trimer of an aromatic monocarboxylic acid has been identified. In the crystal packing the trimers of 3,5-dinitrobenzoic acid form a porous organic framework, in the voids of which are located π-stacked columns of acriflavine cations.

A Rapid and Sensitive Method for Determination of Melamine in Fish, Shrimp, Clam, and Winkle by Gas Chromatography–Mass Spectrometry with Microwave-Assisted Derivatization

A method for rapid and sensitive determination of melamine in aquatic products by gas chromatography–mass spectrometry with microwave-assisted derivatization was proposed in this paper. Melamine was extracted from aquatic product samples using methanol, and the extract was cleaned with a mixed-mode cationic exchange solid phase extraction column. After elution with 5 % ammonia–methanol solution and drying with nitrogen, the residue was derivatized using N,O-bis(trimethylsilyl)trifluoroacetamide containing 1 % trimethylchlorosilane under microwave irradiation for 1 min with a power of 420 W, then detected with gas chromatography–mass spectrometry, and quantified by the external standard method. Some important parameters such as extraction solvent, microwave irradiation power and time, and derivatization reagent volume were investigated and optimized. The results showed that methanol could effectively extracted melamine from aquatic products as well as precipitated the protein in samples. Under the optimum conditions, the detection limit for melamine was as low as 0.006 mg/kg, and the linear range was from 0.02 to 50 mg/kg with a correlation coefficient of 0.9997. The proposed method was applied to the analysis of melamine in aquatic products (fish, shrimp, clam, and winkle), and the recovery for melamine was 89.65–105.16 % with relative standard deviation of 3.0–6.0 %.

Atomic structure of ion tracks in Ceria

We have investigated atomic structure of ion tracks in CeO2 irradiated with 200MeV Xe ions by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). TEM observations under inclined conditions showed continuous ion tracks with diffraction and structure factor contrast, and the decrease in the atomic density of the ion tracks was evaluated to be about 10%. High resolution STEM with high-angle annular dark-field (HAADF) technique showed that the crystal structure of the Ce cation column is retained at the core region of ion tracks, although the signal intensity of the Ce cation lattice is reduced over a region 4–5nm in size. Annular bright field (ABF) STEM observation has detected that the O anion column is preferentially distorted at the core region of ion tracks within a diameter of 4nm. The core region of ion track in CeO2 is determined to contain a high concentration of vacancies or small vacancy clusters and to generate interstitials in surrounding regions.

Crystal Architectures and Magnetic Properties of Alkylferrocenium Salts with FnTCNQ (n = 0, 2, 4): Effect of Substituents on the Self-Assembled Structures

The crystal architecture and magnetic properties of the alkylferrocenium salts of tetracyanoquinodimethane (TCNQ)-type acceptors have been investigated using 1,1′-dimethyl-, 1,1′-diethyl-, 1,1′-diisopropyl-, tert-butyl-, and tert-pentyl-ferrocene as the donors. In all of the resulting salts, the donors and acceptors were stacked to form independent columns. The F4TCNQ salts had a D/A ratio of 1:1 and existed as hexagonal assembled structures composed of anion columns surrounded by cation columns. The F2TCNQ and TCNQ salts had a D/A ratio of 1:2 and existed as a rectangular arrangement of cation columns. Weak antiferromagnetic interactions were found to operate between the cations in these salts.

Structure and magnetic properties of a new anion-deficient perovskite Pb2Ba2BiFe4ScO13 with crystallographic shear structure

Pb2Ba2BiFe4ScO13, a new n=5 member of the oxygen-deficient perovskite-based AnBnO3n−2 homologous series, was synthesized using a solid-state method. The crystal structure of Pb2Ba2BiFe4ScO13 was investigated by a combination of synchrotron X-ray powder diffraction, electron diffraction, high-angle annular dark-field scanning transmission electron microscopy and Mössbauer spectroscopy. At 900K, it crystallizes in the Ammm space group with the unit cell parameters a=5.8459(1)Å, b=4.0426(1)Å, and c=27.3435(1)Å. In the Pb2Ba2BiFe4ScO13 structure, quasi-two-dimensional perovskite blocks are periodically interleaved with ½[110] (1¯ 0 1)p crystallographic shear (CS) planes. At the CS planes, the corner-sharing FeO6 octahedra are transformed into chains of edge-sharing FeO5 distorted tetragonal pyramids. B-positions of the perovskite blocks between the CS planes are jointly occupied by Fe3+ and Sc3+. The chains of the FeO5 pyramids and (Fe,Sc)O6 octahedra delimit six-sided tunnels that are occupied by double columns of cations with a lone electron pair (Pb2+). The remaining A-cations (Bi3+, Ba2+) occupy positions in the perovskite block. According to the magnetic susceptibility measurements, Pb2Ba2BiFe4ScO13 is antiferromagnetically ordered below TN ≈350K.

Iodine networks in polyiodides of M(III) urea complexes: Crystal structures of [V(Ur)6][I3]3 and [Dy(Ur)8][I5][I3]2[I2

Unique [V(Ur)6][I3]3 and [Ln(Ur)8][I5][I3]2[I2] (Ln=Dy, La) were prepared by reactions of hexaureavanadium(III) and tetraaquatetraurealanthanide(III) iodides with iodine and the crystal structures of the vanadium and dysprosium compounds are reported. Metal ions are located at the centres of distorted octahedral and square-antiprismatic arrangements, respectively, of oxygen atoms of covalent-coordinated urea. The triiodide anions in the vanadium polyiodide are united in infinite helical chains fitting between the columns of complex cations and binding them together by hydrogen bonding. In the dysprosium polyiodide, the V-shaped I5− ions are united in infinite planar twisting chains. The chains are connected by short contacts through bridging V-shaped I5− ions (combined of I2 molecule and I3− ion) and symmetric I3− ions. Another I3− ion is isolated. The bonded iodine atoms form hexahedral channels, and the columns of the complex cations are localized in these channels and stabilized by hydrogen bonding.

Extraneous Carbon Assessments in Radiocarbon Measurements of Black Carbon in Environmental Matrices

Extraneous carbon (Cex) added during chemical processing and isolation of black carbon (BC) in environmental matrices was quantified to assess its impact on compound specific radiocarbon analysis (CSRA). Extraneous carbon is added during the multiple steps of BC extraction, such as incomplete removal of solvents, and carbon bleed from the gas chromatographic and cation columns. We use 2 methods to evaluate the size and Δ14C values of Cex in BC in ocean sediments that require additional pretreatment using a cation column with the benzene polycarboxylic acid (BPCA) method. First, the direct method evaluates the size and Δ14C value of Cex directly from the process blank, generated by processing initially empty vials through the entire method identically to the treatment of a sample. Second, the indirect method quantifies Cex as the difference between processed and unprocessed (bulk) Δ14C values in a variety of modern and 14C-free or “dead” BC standards. Considering a suite of hypothetical marine sedimentary samples of various sizes and Δ14C values and BC Ring Trial standards, we compare both methods of corrections and find agreement between samples that are >50 μg C. Because Cex can profoundly influence the measured Δ14C value of compound specific samples, we strongly advocate the use of multiple types of process standards that match the sample size to assess Cex and investigate corrections throughout extensive sample processing.

Extraneous Carbon Assessments in Radiocarbon Measurements of Black Carbon in Environmental Matrices

Extraneous carbon (Cex) added during chemical processing and isolation of black carbon (BC) in environmental matrices was quantified to assess its impact on compound specific radiocarbon analysis (CSRA). Extraneous carbon is added during the multiple steps of BC extraction, such as incomplete removal of solvents, and carbon bleed from the gas chromatographic and cation columns. We use 2 methods to evaluate the size and Δ14C values of Cex in BC in ocean sediments that require additional pretreatment using a cation column with the benzene polycarboxylic acid (BPCA) method. First, the direct method evaluates the size and Δ14C value of Cex directly from the process blank, generated by processing initially empty vials through the entire method identically to the treatment of a sample. Second, the indirect method quantifies Cex as the difference between processed and unprocessed (bulk) Δ14C values in a variety of modern and 14C-free or “dead” BC standards. Considering a suite of hypothetical marine sedimentary samples of various sizes and Δ14C values and BC Ring Trial standards, we compare both methods of corrections and find agreement between samples that are >50 µg C. Because Cex can profoundly influence the measured Δ14C value of compound specific samples, we strongly advocate the use of multiple types of process standards that match the sample size to assess Cex and investigate corrections throughout extensive sample processing.

Hydrophilic interaction chromatography coupled matrix assisted laser desorption/ionization mass spectrometry for molecular analysis of organic compounds in medicines, tea, and coffee

Natural occurring organic compounds from food, natural organic matter, as well as metabolic products have received intense attention in current chemical and biological studies. Examination of unknown compounds in complex sample matrices is hampered by the limited choices for data readout and molecular elucidation. Herein, we report a generic method of hydrophilic interaction chromatography (HILIC) coupled with matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the rapid characterization of ingredients in pharmaceutical compounds, tea, and coffee. The analytes were first fractionated using a cationic HILIC column prior to MALDI-MS analyses. It was found that the retention times of a compound arising from different samples were consistent under the same conditions. Accordingly, molecules can be readily characterized by both the mass and chromatographic retention time. The retention behaviors of acidic and basic compounds on the cationic HILIC column were found to be significantly influenced by the pH of mobile phases, whereas neutral compounds depicted a constant retention time at different pH. The general HILIC-MALDI-MS method is feasible for fast screening of naturally occurring organic compounds. A series of homologs can be determined if they have the same retention behavior. Their structural features can be elucidated by considering their mass differences and hydrophilic properties as determined by HILIC chromatogram.