Anion-exchange Matrix Research Articles

Sorption Extraction of Gallium from Alumina-Alkaline Solutions

AbstractThe possibility of sorption concentration of gallium from alumina-alkaline solutions resulting by leaching of recycled soda with sludge water during alumina production—which are middlings of alumina production—has been studied. During bauxite processing, soda is accumulated in recycled alkali solutions, extracted by evaporation and used in sintering. The sludge water is formed during storage of wastes pumped in the form of slurry to the settling tank and can be used in production as wash water. Sorption processes with application of ion exchange resins with high capacity and selectivity, presented in the world market in a large assortment, seem to be a promising direction of gallium concentration from alumina-alkaline solutions. On the basis of the analysis carried out, anion exchangers AN-31 and D-403 OH form were selected for sorption concentration of gallium from alumina-alkaline solutions. A comparative analysis of the sorption properties showed that the D-403 anion exchange resin exhibited better selectivity and a higher dynamic exchange capacity for gallium. The high capacity for gallium absorption with the D-403 anion exchanger resulted from its greater basicity, since the oxyhydryl groups at the β-, γ- and δ-positions in the resin matrix exert a greater negative inductive effect on the tertiary nitrogen atom, which has a lone electron pair, compared to the oxyhydryl and hydroxy groups in the β- and γ-positions relative to the secondary nitrogen atom of the anion exchange resin AN- 31. Due to the unshared electron pair of the nitrogen atom, an additional covalent effect arose, causing stronger chemical bonding between the gallium ions and the D-403 anion exchange matrix. Studies were carried out to determine the optimal conditions for the desorption of gallium with a 2 N sodium hydroxide solution. The gallium content in the alkaline eluates was suitable for electrolytic production of metallic gallium.

Transformation of CuO and Cu2O particles into CuxS within the polymeric matrix of anion exchangers, and its structural and morphological implications

The study demonstrates the process of anion exchanger modification in order to obtain a reactive organic polymer containing CuxS dispersed within its matrix. As starting materials, two strongly basic commercial anion exchangers were used – macroreticular and gel-type – previously modified by deposition of cuprite or tenorite within their structure. The pre-formed composites were sulphidated using an Na2S solution to obtain materials containing CuxS (5.3–6.7 wt% Cu and 4.5–6.7 wt% S), which were further studied using Raman and XPS spectroscopy, and XRD and SEM/EDS analyses. Depending on the sulphidation precursor, Cu2O or CuO, its distribution within the polymeric matrix, and the porous structure of the supporting anion exchanger, products with different CuxS content were obtained. The main sulphidation product – covellite – was accompanied by admixtures of copper-rich phases such as digenite and djurleite, but products of sulphide oxidation were also identified. The conversion of Cu2O into CuS was more efficient and selective in comparison to CuO. The sulphidation process remained within the initial distribution of the precursor particles within the polymeric matrix. The morphology of the obtained covellite particles was strongly dependent on the porous structure of the supporting anion exchanger. The conversion of the Cu2O and CuO within the macroporous matrix led respectively to spiky burr-like CuS and more densely packed elongated needle-shaped CuS particles, while the CuS particles obtained in the gel-type matrix were spherical. The spherical particles obtained from Cu2O conversion exhibited a hollow structure, which was the result of solid-state diffusion during the sulphidation, the so-called Kirkendall effect.

Size-Controlled Transformation of Cu2O into Zero Valent Copper within the Matrix of Anion Exchangers via Green Chemical Reduction.

Composite materials containing zero valent copper (ZVC) dispersed in the matrix of two commercially available strongly basic anion exchangers with a macroreticular (Amberlite IRA 900Cl) and gel-like (Amberlite IRA 402OH) structure were obtained. Cu0 particles appeared in the resin phase as the product of the reduction of the precursor, i.e., copper oxide(I) particles previously deposited in the two supporting materials. As a result of a one-step transformation of preformed Cu2O particles as templates conducted using green reductant ascorbic acid and under mild conditions, macroporous and gel-type hybrid products containing ZVC were obtained with a total copper content of 7.7 and 5.3 wt%, respectively. X-ray diffraction and FTIR spectroscopy confirmed the successful transformation of the starting oxide particles into a metallic deposit. A scanning electron microscopy study showed that the morphology of the deposit is mainly influenced by the type of matrix exchanger. In turn, the drying steps were crucial to its porosity and mechanical resistance. Because both the shape and size of copper particles and the internal structure of the supporting solid materials can have a decisive impact on the potential applications of the obtained materials, the results presented here reveal a great possibility for the design and synthesis of functional nanocrystalline solids.

Features of Synthesis of Anion Exchange Matrix “Polikon A” with Oxidated Ultrafine Additives on Lavsan Textile Bases

A comparative analysis of the studies on the influence of the textile structure of reinforcing fabric on the physicomechanical and sorption characteristics of anion-exchange systems as a component of the “Polikon” mosaic materials is presented in this study. This study shows the promise of using polyester fibers as a reinforcing fiber base for the production of Polikon A membrane materials. The morphology, moisture capacity, static exchange capacity, and physical and mechanical characteristics of anion-exchange membrane systems were investigated. A modification of Polikon A anion-exchange matrices on lavsan fabric by oxidized ultrafine particles of silicon, iron and nickel is proposed.

Deposition of spherical and bracelet-like Cu2O nanoparticles within the matrix of anion exchangers via reduction of tetrachlorocuprate anions

Considering the biocidal, sorption and photocatalytic performance of parent Cu2O, in order to prevent the release of its nanostructures into the cleaned media, a Cu2O deposit was introduced into the matrix of a synthetic porous material whereby a hybrid ion exchanger (HIX) was obtained. Two commercially available strongly basic anion exchangers with respectively a macroreticular (Amberlite IRA 900Cl, M/An) and gel-like structure (Amberlite IRA 402OH, G/An) were used as the supporting materials. The Cu2O deposit was introduced into the anion exchanger in two steps, conducted batchwise at ambient temperature. First, the anion exchanger functional groups were transformed into the CuCl42- form and then the polymeric intermediate product was contacted with an alkaline reducer solution to precipitate Cu2O. The effects of many factors were investigated to optimize the process of obtaining HIX. When ascorbic acid (not glucose) was used as the reducer, it was possible to introduce as much as 9.7 wt% and 7.3 wt% of Cu2O into respectively the M/An and the G/An. The products were characterized by X-ray diffraction, scanning electron microscopy with EDS analysis, as well as FTIR and Raman spectroscopy. The morphologies of the obtained products were found to be sensitive to the type of basic anion exchangers used. Microscopic analysis showed that the Cu2O in both types of used polymeric matrices was in the form of spherical particles of a size not exceeding 1.0 μm. However, depending on the type of supporting exchanger these particles occurred singly or in the form of bracelets-like clusters.

Preliminary Characterization of Occipodins, Natural Product Anticoagulants from Hematophagous Marine Parasites, Isopod Elthusa vulgaris and Copepod Phrixocephalus Cincinnatus.

We report identification and preliminary characterization of novel proteinaceous anticoagulants from two marine crustacea, Elthusa vulgaris and Phrixocephalus cincinnatus. We also propose naming them Occipodins in honor of the college where this undergraduate research has been initiated. The organisms were collected at 25-125 meters depth off the coast of Los Angeles. Both organisms are hematophagous arthropods that anchor onto their host species and induce the extravasation of host blood into their digestive organs. Female P. cincinnatus display host specificity infecting the eyes of flatfish by anchoring to the choroid membrane and subsequently developing rami, an elaborate dendritic network, that facilitates the ingestion of extravasated blood from retinal blood vessels (Figure 1). The described species E. vulgaris is an isopod that similarly parasitizes a variety of marine fish by anchoring to the blood-rich gill filaments of their hosts (Figure 2). The accumulation of blood and attenuation of coagulation responses visually observed in the copepod trunk prompted us to initiate the identification of the anticoagulant factors in both hematophagous marine species.A crude cellular extract was prepared by homogenizing 10 specimens with a mortar and pestle frozen in liquid nitrogen resulting in a fine powder. The homogenate was resuspended in 15ml of 50mM Hepes buffer, pH7.4, containing 150mM NaCl and 3mM CaCl2 and mixed on a rotary shaker for 20min at room temperature. The resulting tissue suspension was centrifuged at 15,000xg 15 min and the supernatant was filtered through a 0.2 μm syringe filter. 10μl aliquots of extracts were used for all anticoagulant activity tests using FACT plasma for aPTT and PT assays on a Stago STart 4 hemostasis analyzer (Table 1). The extracts from both parasites were found to have exclusive anticoagulation activity on the intrinsic pathway (APTT assay) but no prolongation of coagulation time was observed in PT assays. Several biochemical tests were employed to further characterize the occipodins. First, size exclusion tests were performed using series of Millipore centrifugal filter units ranging from 10 to 100kD molecular weight cutoff. The size of the occipodin from P. cincinnatus was determined to be larger than 100kD while the anticoagulant isolated from Elthusa was estimated to be ~50kD. In order to identify whether these large macromolecules require a folded structure for activity we employed heat denaturation tests at 96°C for 15min. The P. cincinnatus occipodin showed substantial loss of anticoagulant activity following heat denaturation while E. vulgaris retained some residual anticoagulant activity, indicating the presence of non-proteinaceous, heat-resistant components (Table 1).A preliminary purification procedure of the anticoagulant isolated from Elthusa was established using a DEAE anion exchange chromatography. The crude tissue extract was diluted two fold with 50mM Hepes buffer, pH7.4 and applied on a 22ml column packed with DEAE-Sephacel (GE Healthcare) anion exchange matrix equilibrated with 50mM HEPES buffer, pH 7.4, containing 75mM NaCl. To elute occipodins, a step gradient ranging from 150 to 500mM NaCl (in the same HEPES buffer) was applied, after an extensive washing step with 120ml equilibration buffer. The anticoagulant activity was detected in fractions eluted between 125mM and 500mM NaCl with main pick centered at fractions eluted with buffer containing 150mM NaCl (Table 2)Identification of the site of inhibitory action of occipodins on the intrinsic coagulation pathway is currently in progress. In addition, further experiments will be targeted towards purification of occipodins and identification of their partial amino acid sequences. This sequence information will be used for cloning of cDNAs encoding these proteins. [Display omitted] [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Low-temperature oxidation of methanal on nanostructured silver–amino anion exchanger catalysts

Nanostructured silver–amino anion exchanger composites have been synthesized as catalysts for the low-temperature oxidation of methanal with molecular oxygen in aqueous solution. The oxidative conversion of methanal reaches 80–100% at 298 K. The methanal oxidation reaction is size-dependent, and its rate increases with a decrease in the silver nanoparticle size. The fixed amino groups of anion-exchange matrix play the role of additional active sites for the adsorption of methanal in the form of methylene glycolate–anions, which facilitates the reaction.

Determination of precipitation regularities for nanoparticles of hydrated metal oxides in the anion exchange resin

Organic and inorganic ion-exchange materials containing incorporated inorganic particles of ion exchangers are characterized by enhanced selectivity for ions of toxic metals and resistant to poisoning by organic substances. An important task for achieve the necessary kinetic parameters of ion exchange is to reduce the size of the incorporated particles that is particularly important for hydrated oxides containing functional groups, mainly, on the outer surface of the particles. Regularities of forming Zr(IV), Fe(III), Al(III) oxide particles in a polymeric anion exchange matrix are considered in the article. The aim of research is establishing and experimental confirmation of deposition mechanism for inorganic ionite in the polymer for directional control of size and state of the particles. Using computer analysis of TEM images it was revealed that the fractal dimension of the aggregate particles is 2,38-2,72. Nature of modifier also determines the state of the polymer particles. The effect of these factors was analyzed using the Ostwald-Freundlich equation. It was established that the primary nanoparticle size is determined by reprecipitation. Accordingly, the formation mechanism of aggregates is association of nanoparticles with a small cluster, and the limiting step is the diffusion of the polymer nanoparticles. The equation for the diffusion flux of nanoparticles was obtained and it was shown that flux slowing leads to formation of dendritic multilevel structures. The results can be used to develop technologies for ionite synthesis, ion-exchange membranes and materials for baromembrane separation. The proposed approach allows to obtain materials with a given particle size and, consequently, with certain functional properties.

Click Chemistry Applied to the Synthesis of Salmonella Typhimurium O-Antigen Glycoconjugate Vaccine on Solid Phase with Sugar Recycling.

A solid-phase conjugation method was developed and applied to the synthesis of an O-antigen based glycoconjugate vaccine against Salmonella Typhimurium, with CRM197 as the carrier protein. Copper-free click chemistry was used as the conjugation chemistry, after derivatizing the sugar and the protein components with alkyne and azido linkers, respectively. This chemistry has the advantage of not deactivating functional groups during the conjugation step, thereby allowing the recycling of unreacted components. The activated carrier protein was adsorbed to an anion exchange matrix and quantitatively conjugated to the O-antigen. The resulting conjugate was eluted from the resin free of unconjugated sugar which was previously removed by simple washing steps. Unreacted O-antigen was recycled by addition to a new batch of resin-CRM197 resulting in further quantitative protein conjugation. This process has advantages in relation to reduction of costs for production of conjugate vaccines, allowing unreacted sugar recovery and simplifying the purification of the glycoconjugate.

Matrix-assisted refolding and purification of proteins by a novel designed anion exchange chromatography

Purpose: The refolding of recombinant human interferon α-2b is accompanied by low yield that could be due to high aggregation and multiplicity of steps in downstream processing. It is therefore essential to refold and purify the protein to simultaneously increase the production yield and reduce the required downstream steps. Methods: Inclusion bodies were dissolved in Tris-HCl buffer containing 6 M guanidine and applied to a newly designed poly-arginine anion exchange chromatography system. Different reduced-oxidized glutathione amount were employed for refolding the target protein. The refolded proteins were applied to gel filtration chromatography and subjected to biological activity assessment. Results: By increasing the sample volume, the refolding efficacy, purification factor and potency were significantly decreased. This reduction can be highest when only 2 column volumes of the glutathione redox pair presented in the column. The highest values of these factors were obtained when 4 column volumes of the glutathione redox pair offered to the column. To achieve better results, the proportion of sample volume and the amount of passed glutathione redox pair through column should be optimized. Consistent with the increase of sample volume to 1250 μl at any levels of glutathione redox pair there was a significant drop in all factor values. Conclusion: Poly-arginine anion exchange matrix is a new artificial chaperone that can improve the refolding and purification process simultaneously with high efficacy. Therefore, we present poly-arginine anion exchange chromatography as an alternative method for protein refolding with promising commercial and developmental potential.

Using epichlorohydrin for a simultaneous increase of functional group hydrophilicity and spatial separation from the matrix of anion exchangers for ion chromatography

To increase the efficiency of anion exchangers based on copolymers of styrene and divinylbenzene in ion chromatography a new method for spatial separation and hydrophilization of functional groups using epichlorohydrin is suggested. Synthesis consists of acylation of a matrix by acetic anhydride, reductive amination by methylamine hydrochloride, alkylation of the aminated phase using epichlorohydrin, amination by dimethylamine at the terminal chlorine atom, and quaternization of the terminal amino group with epichlorohydrin. The obtained anion exchangers make it possible to simultaneously determine eight anions (F−, HCOO−, Cl−, NO2− Br−, N3− HPO43− and SO42−) and demonstrate high efficiency (more than 62000 N/m for HPO42−) in a suppressed ion-chromatography mode.

A novel application of methacrylate based short monolithic columns: Concentrating Potato spindle tuber viroid from water samples

Potato spindle tuber viroid (PSTVd) is the causal agent of a number of agriculturally important diseases. It is a single-stranded, circular and unencapsidated RNA molecule with only 356–360 nucleotides and no coding capacity. Because of its peculiar structural features, it is very stable ex vivo and it is easily transmitted mechanically by contaminated hands, tools, machinery, etc. In this work, we describe the development and optimization of a method for concentrating PSTVd using Convective Interaction Media (CIM) monolithic columns. The ion-exchange chromatography on diethylamine (DEAE) monolithic analytical column (CIMac DEAE-0.1mL) resulted in up to 30% PSTVd recovery whilst the hydrophobic interaction chromatography on C4 monolithic analytical column (CIMac C4-0.1mL) improved it up to 60%. This was due to the fact that the binding of the viroid to the C4 matrix was less strong than to the highly charged anion-exchange matrix and could be easier and more completely eluted under the applied chromatographic conditions. Based on these preliminary results, a C4 HLD-1 (High Ligand Density) 1mL monolithic tube column was selected for further experiments. One-litre-water samples were mixed with different viroid quantities and loaded onto the column. By using reverse transcription quantitative polymerase chain reaction (RT-qPCR), the viroid RNA was quantified in the elution fraction (≈5mL) indicating that 70% of the viroid was recovered and concentrated by at least two orders of magnitude. This approach will be helpful in screening irrigation waters and/or hydroponic systems’ nutrient solutions for the presence of even extremely low concentrations of PSTVd.

Isolation, Purification and Characterisation of Low Molecular Weight Xylanase from Bacillus pumilus SSP-34

Low molecular weight endo-xylanase from Bacillus pumilus SSP-34 was purified to homogeneity using ion exchange and size exclusion chromatographies. Xylanases were isolated by novel purification protocol which includes the use of anion exchange matrix such as DEAE Sepharose CL 6B with less affinity towards enzyme protein. The purified B. pumilus SSP-34 have a molecular weight of 20 kDa, with optimum pH and temperature at 6.0 and 50 °C, respectively. The enzyme was stable at 50 °C for 30 min. It showed remarkable stability at pH values ranging from 4.5 to 9 when the reaction was carried out at 50 °C. K (m) and V (max) values, determined with oats spelts xylan were 6.5 mg ml⁻¹ and 1,233 μmol min⁻¹ mg⁻¹ protein, respectively, and the specific activity was 1,723 U mg⁻¹.

Mobile phases for the determination of polarizable anions on polystyrene/divinylbenzene anion-exchange resins

Anion-exchange resins have been prepared by chloromethylating 50%-crosslinked styrene-divinylbenzene copolymers (PS/DVB) followed by amination with trimethylamine. In addition to ion exchange, interactions with the anion-exchange matrix considerably contribute to the retention of polarizable anions on these sorbents. Additives in the eluent that can suppress adsorption sites of the stationary phase can decrease this effect. p-Hydroxybenzonitrile (0.15 mmol/L) in the eluent increases the NO3− peak efficiency from 820 to 5100 theoretical plates per meter.

Determination of ultratrace impurity elements in high purity niobium materials by on-line matrix separation and direct injection/inductively coupled plasma mass spectrometry

The determination of 52 impurity elements in niobium materials (niobium metal, niobium oxide (V), and niobium pentaethoxide) was performed by inductively coupled plasma mass spectrometry (ICP-MS) with on-line anion exchange matrix separation as well as direct nebulization. Niobium material samples were decomposed with a mixture of hydrofluoric acid and nitric acid to prepare 10% niobium solutions. In the on-line anion exchange matrix separation/ICP-MS, the niobium and hydrofluoric acid concentrations in sample solution were adjusted to 5% and ca. 8 M, respectively. The solution was then injected into the carrier stream from the sample loop of injection valve to pass through an anion exchange resin column. In the anion exchange separation, niobium in the fluoro-complex form was adsorbed on the resin, while impurity elements were eluted. The eluted elements were introduced into ICP-MS for the determination of 25 impurity elements. On the other hand, 27 impurity elements could not be separated well from niobium matrix under the above anion exchange conditions, and then the sample solution with the niobium concentration of max. 0.2% containing internal standard elements was injected from the sample loop of injection valve directly to introduce into ICP-MS. As a result, 52 impurity elements in three kinds of niobium materials could be determined at the ng g −1 level.

Analysis of human bone alkaline phosphatase isoforms: Comparison of isoelectric focusing and ion-exchange high-performance liquid chromatography

Background Several isoforms of alkaline phosphatase (ALP) can be identified in human tissues and serum after separation by anion-exchange HPLC and isoelectric focusing (IEF). Methods We purified four soluble bone ALP (BALP) isoforms (B/I, B1x, B1 and B2) from human SaOS-2 cells, determined their specific pI values by broad range IEF (pH 3.5–9.5), compared these with commercial preparations of bone, intestinal and liver ALPs and established the effects of neuraminidase and wheat germ lectin (WGA) on enzyme activity. Results Whilst the isoforms B1x (pI = 4.48), B1 (pI = 4.32) and B2 (pI = 4.12) resolved as well-defined bands, B/I resolved as a complex (pI = 4.85–6.84). Neuraminidase altered the migration of all BALP isoforms to pI = 6.84 and abolished their binding to the anion-exchange matrix, but increased their enzymatic activities by 11–20%. WGA precipitated the BALP isoforms in IEF gels and the HPLC column and attenuated their enzymatic activities by 54–73%. IEF resolved the commercial BALP into 2 major bands (pI = 4.41 and 4.55). Conclusions Migration of BALP isoforms is similar in IEF and anion-exchange HPLC and dependent on sialic acid content. HPLC is preferable in smaller scale research applications where samples containing mixtures of BALP isoforms are analysed. Circulating liver ALP (pI = 3.85) can be resolved from BALP by either method. IEF represents a simpler approach for routine purposes even though some overlapping of the isoforms may occur.

Preparation of an anion-exchange adsorbent by the radiation-induced grafting of vinylbenzyltrimethylammonium chloride onto cotton cellulose and its application for protein adsorption

Poly(vinylbenzyltrimethylammonium chloride)-graft-cotton cellulose, an anion-exchange matrix, was synthesized by a mutual radiation-induced grafting technique with a 60Co γ-radiation source. The grafted matrix was characterized by grafting yield estimation, elemental analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The grafting yield decreased with the increase in the dose rate. However, the grafting yield and nitrogen content of grafted samples increased almost linearly with an increase in the total irradiation dose. To evaluate the performance of the grafted anion-exchange matrix, the protein adsorption and elution behavior were investigated in a continuous column process under various experimental conditions, with bovine serum albumin used as a model protein. The binding and elution behavior of the anion-exchange matrix depended on different experimental parameters, such as the grafting yield, ionic strength, pH of the medium, and amount of protein loaded. From a breakthrough curve, the equilibrium binding capacity and elution percentage of the grafted anion-exchange matrix were estimated to be 40 mg/g and 94%, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5512–5521, 2006

Toward high yield synthesis of peptide–oligonucleotide chimera through a disulfide bridge: A simplified method for oligonucleotide activation

During the last decade, cell penetrating peptides (CPP) have been extensively used to mediate the cellular delivery of non-permeant biomolecules, including oligonucleotides (ONs). A covalent linkage between the CPP and the transported ON is required to mediate efficient cell internalization, and a disulfide bridge between the CPP and the ON has been shown to induce the most potent biological response. In this paper, we describe the activation. In a one step process of the sulfhydryl function from a synthon commercially available for ON synthesis. In addition, since the highly cationic nature of currently used CPP caused serious precipitation problems during the coupling step, we further improved the method by adsorbing the crude activated ON on an anion exchange matrix prior to specific peptide coupling.

Determination of intracellular concentrations of the TRPM2 agonist ADP-ribose by reversed-phase HPLC

Since the NAD metabolite ADP-ribose (ADPR) has recently gained attention as a putative messenger, a method was established for the quantification of intracellular ADPR by reversed-phase HPLC. Cellular nucleotides were extracted with trichloroacetic acid, and crude cell extracts purified by solid phase extraction using a strong anion exchange matrix. After optimization of the extraction procedure, cellular ADPR levels were determined using two different reversed-phase columns (C18 versus C12), operated in ion pair mode. Intracellular ADPR concentrations in human Jurkat T-lymphocytes and murine BW5147 thymocytes were determined to be 44 ± 11 μM and 73 ± 11 μM, respectively.

Concentration and purification of orotic acid directly from whey with an expanded bed adsorption system

The development of an expanded bed process for the concentration and purification of orotic acid directly from whey is described. Different commercially available adsorbents were tested in series of pilot batch adsorption experiments to determine the most suitable separation system. Best results were achieved using a weak anion-exchange matrix. An elution protocol was established using MgCl 2 as eluting agent to recover the adsorbed orotic acid with ∼85% yield and 10-fold concentration. Purified orotic acid was precipitated under acid conditions with a yield of 95%.