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PubMed2006

Removal of low-concentration ammonia in water by ion-exchange using Na-mordenite.

Removal of low-concentration ammonia (2-10ppm) in water by ion exchange with Na-form zeolites was investigated using a flow system at 278-333K. Results indicated that Na-mordenite was the most efficient cation-exchanger (compared with Na-ferrierite, Na-ZSM-5, Na-beta, and Na-Y, as well as the K- and H-form mordenite) for the removal of low-concentration ammonia. The ammonia uptake and the ion-exchange level achieved using mordenite with NH(4)(+) for removal of 10ppm ammonia at 333K were 1.21mmolg(-1) and 79.1%, respectively. The high efficiency of Na-mordenite for removal of low-concentration ammonia in water is due to the strong acidity of the corresponding H-form mordenite as demonstrated by ammonia temperature-programmed desorption. Ammonia uptake on the Na-mordenite was minimally influenced by operating temperature in the range of 278-333K. The coexistent K(+) and Na(+) in water had little influence on ammonia uptake of the Na-mordenite. In contrast, coexistent Ca(2+) and Mg(2+) significantly lowered the efficiency of the Na-mordenite for ammonia removal.

Aluminum Silicates↗
PubMed1988

Determination of salsolinol by ion-exchange chromatography with glycylglycine as the post-derivatizing agent.

The determination of salsolinol in human urine was carried out by ion-exchange chromatography on two coupled columns of a weakly acidic ion exchanger with a hydrophilic matrix (Asahipak ES-502C). Salsolinol was first isolated from urine by adsorption on Amberlite CG-50. It was eluted together with catecholamines by 2/3 M boric acid solution. The amines were then separated by isocratic elution from the first column of Asahipak with 0.05 M sodium succinate buffer (pH 5.5) containing 0.015 M borate and 0.5 mM ethylenediaminetetraacetate. Epinephrine, norepinephrine, dopamine and salsolinol were eluted in that order. The salsolinol-containing fraction was then transferred, by column switching, to a second Asahipak column and eluted with the same mobile phase. Salsolinol was determined fluorimetrically by reaction with glycylglycine in the presence of hexacyanoferrate(III) at pH 7.5-8 and 65 degrees C. Samples could be analysed every 47 min. The detection limit for salsolinol was 2 pmol/ml.

Chromatography, Ion Exchange↗
PubMed2001

Membrane ion-exchange chromatography for process-scale antibody purification.

The large-scale production of recombinant monoclonal antibodies demands economical purification processes with high throughputs. The potential for ion-exchange membrane adsorbers to replace traditional ion-exchange columns was evaluated. Breakthrough capacities of commercially available cation-exchange membranes were determined as a function of flow-rate and layer number. Due to economic and process restrictions, cation-exchange membranes may not currently be advantageous for process-scale antibody purification in a bind and elute mode. However, anion-exchange membranes in a flow-through mode may provide a reasonable alternative to columns for the removal of low levels of impurities such as DNA, host cell protein, and virus.

Antibodies↗
PubMed1985

Ion-exchange high-performance liquid chromatographic studies on sulphydryl-catalysed structural alterations of bovine mercaptalbumin.

The N-A isomerization (the intramolecular SH/S-S exchange reaction) of bovine mercaptalbumin (BMA) in alkaline medium was studied by using ion-exchange high-performance liquid chromatography (HPLC) and moving-boundary electrophoresis. Results obtained by ion-exchange HPLC on the N-A isomerization of BMA were consistent with those by moving-boundary electrophoresis and showed at least two kinds of the A-form, A1 and A2, indicating that the N-A isomerization is a multi-step reaction. The rate of the N-A isomerization was strongly suppressed in [2H]water solution. The suppression by [2H]water might support the current view that intra- and intermolecular hydrophobic and/or hydrogen bonds are strengthened in [2H]water.

Animals↗
PubMed1996

Successive elution by ion-exchange chromatography of H3-H4 histone complexes differing in their degree of acetylation.

On Biorex 70 ion exchanger at neutral pH the histones H3 and H4 are usually eluted by 4 M guanidinium chloride (gdm Cl). In order to protect cysteines and methionines from oxidation we systematically added 2-mercaptoethanol to the elution buffer. This resulted in the two histones being unexpectedly eluted together at around 1 M gdm Cl. The use of a shallower gradient resulted in a division in the peak of histones, with the acetylated species of H3 and H4 being eluted first and the nonacetylated species of H3 and H4 eluted last. When histone H3 or histone H4 was applied alone or when the chromatography was performed at low pH, these histones were eluted in the usual position at about 4 M gdm Cl. These events mean that the simultaneous elution of the histones H3 and H4 at about 1 M gdm Cl involves the formation of H3-H4 complexes. Therefore, the H3-H4 complex may be obtained by ion-exchange chromatography as the H2A-H2B complex was previously; furthermore, the former was fractionated according to postsynthetic modifications. This finding provides a new basis for explaining some of the previous elution profiles of chromatin extracts.

Acetylation↗
PubMed2004

A theory of overshoot phenomena in an ion-exchange membrane system.

A simple theory based on a kinetics equation with time delay is presented for ion permeation through an ion-exchange membrane for the case where two or more species of ions of the same charge are permeating from solutions 1 to 2 through the membrane. This theory explains the observation of Neihof and Sollner that if the exchange rates of ionic species are quite different from each other, then the concentration of the fastest exchanging species of ions in solution 2 exhibits overshoot [R. Neihof, K. Sollner, J. Phys. Chem. 61 (1957) 159].

Biocompatible Materials↗
PubMed1985

Estimation of catecholamines by ion-exchange chromatography on Asahipak ES-502C, using glycylglycine as the post-derivatizing agent.

The estimation of catecholamines in human urine was carried out by ion-exchange chromatography on a column of a weakly acidic ion exchanger with an hydrophilic matrix. The catecholamines were first adsorbed onto Amberlite CG-50 (buffered at pH 6.5 with 0.4 M phosphate buffer) and selectively eluted by 0.66 M boric acid solution. They were then separated from impurities that responded to fluorometric detection by isocratic elution from a column of Asahipak ES-502C, a cross-linked vinyl alcohol copolymer with carboxymethyl groups, at 60 degrees C. The mobile phase was 0.05 M sodium succinate buffer pH 5.25 containing 0.015 M borate and 0.5 mM ethylenediaminetetraacetate. Isoproterenol was used as the internal standard; epinephrine, norepinephrine, isoproterenol and dopamine were eluted in this order. One sample could be analyzed every 35 min. The detection limits were 0.2 ng for epinephrine and norepinephrine, 0.6 ng for dopamine. The elution pattern was quite reproducible; the elution volumes of the catecholamines had not changed after 500 determinations.

Catecholamines↗
PubMed1983

Use of size-exclusion and ion-exchange high-performance liquid chromatography for the isolation of biologically active growth factors.

Size-exclusion and ion-exchange high-performance liquid chromatography were used to purify biologically active growth factors as measured by the ability of the factors to stimulate DNA synthesis in 3T3 cells. Chromatography was performed in aqueous buffer and at neutral pH to avoid possible inactivation of biological activity. The growth factors analyzed were chondrosarcoma growth factor (CHSA-GF), human milk growth factor (HMGF), retinal-derived growth factor (RDGF) and mouse epidermal growth factor (EGF). CHSA-GF, HMGF, and RDGF were eluted from TSK 2000 columns as well-defined peaks of activity with molecular weights of 12,000-15,000, 5000-6000, and 16,000-18,000, respectively. EGF was found to have an abnormally low molecular weight after chromatography on TSK 2000. However, incorporation of guanidine . HCl into the TSK column resulted in the elution of EGF at its known molecular weight of ca. 6000. Anion-exchange high-performance liquid chromatography on AX 300 was used for the purification of HMGF and RDGF, and cation-exchange high-performance liquid chromatography on CM 300 was used for the purification of CHSA-GF. The results show that size-exclusion and ion-exchange chromatography can be used without organic solvents or extremes in pH to purify a number of different growth factors successfully with retention of biological activity.

Animals↗
PubMed2002

Dual gradient ion-exchange chromatography improved refolding yield of lysozyme.

Protein refolding at high concentrations always leads to aggregation, which limits commercial application. An ion-exchange chromatography process with gradient changes in urea concentration and pH was developed to refold denatured lysozyme at high concentration. After adsorption of the denatured protein onto an ion-exchange medium, elution was carried out in combination with a gentle decrease in urea concentration and elevation of pH. Protein would gradually refold along the column with high activity yield. Denatured and reduced lysozyme at 40 mg/ml was loaded into a column filled with SP Sepharose Fast Flow, resulting in 95% activity recovery and 98% mass yield within a short period of time.

Chromatography, Ion Exchange↗
PubMed2003

Protein binding to polymer brush, based on ion-exchange, hydrophobic, and affinity interactions.

The major limitations associated with conventional packed bed chromatography for protein separation and purification can be overcome by using adsorptive microporous membranes as chromatographic media. Microporous membranes have advantages as support matrices in comparison to conventional bead supports because they are not compressible and they eliminate diffusion limitations. As a result, higher throughput and shorter processing times are possible using these membrane systems. In this paper, we review the current state of development in the area of attaching functionalized polymer brushes onto a microporous membrane to form a novel chromatographic medium for protein separation and purification. The functionalized polymer brushes were appended onto the pore surface of a microporous hollow-fiber membrane uniformly across the membrane thickness by radiation-induced graft polymerization and subsequent chemical modifications. We review various applications of this adsorptive membrane chromatography by focusing on polymer brushes bearing ion-exchange, hydrophobic and affinity groups. Proteins were captured in multilayers by the ion-exchange group-containing polymer brushes due to the formation of a three-dimensional space for protein binding via the electrostatic repulsion of the polymer brushes. In contrast, proteins were captured in a monolayer at most by the polymer brushes containing hydrophobic or affinity ligands. By permeating a protein solution through the pores rimmed by the polymer brushes, an ideal capturing rate of the proteins with a negligible diffusional mass-transfer resistance was achieved by the functionalized polymer brushes, based on ion-exchange, hydrophobic, and affinity interactions.

Chromatography, Affinity↗
PubMed1980

Determination of net ionic charge on Tc-99m DTPA and Tc-99m EDTA by a column ion-exchange method.

The net charge on a stable complex ion is conveniently measured at tracer levels by studies of ion-exchange equilibrium. Previous applications to radiopharmaceuticals have used a batch equilibrium method, but such measurements are affected by any radiochemical impurities present. Since technetium pharmaceuticals are often heterogeneous, it is of value to have a technique that is directly applicable to a mixture of different species. Such a method is presented here: a column method to determine the net charge on the technetium-99m complex of diethylenetriaminepenta-acetic acid (DTPA), and also on the principal component in a mixture of species formed by reducing pertechnetate in the presence of ethylenediaminetetra-acetic acid (EDTA). The net charge was calculated from the effect of eluent concentration on retention time. The net charge on Tc-DTPA was found to be -2 at both pH 4.6 and 7.0. The net charge on the Tc-EDTA complex, measured at pH 7.0 only, was also -2.

Chemical Phenomena↗
PubMed2005

Ion-exchange behavior of stannic selenoiodate and stannic selenosilicate: analytical application of stannic selenoiodate.

Two new inorganic ion exchangers, stannic selenoiodate and stannic selenosilicate have been synthesized. The ion-exchange capacity of stannic selenoiodate and stannic selenosilicate for K+ was found to be 1.84 and 1.23 meq g(-1), respectively. pH titration studies reveal monofunctional and bifunctional behavior for stannic selenosilicate and stannic selenoiodate, respectively. Distribution coefficients of metal ions in dimethylformamide-HCl and formamide-HCl systems have been determined. Some important and analytically difficult quantitative binary and ternary separations, and selective separations of Ag+, Sn4+, Zr4+, Co2+, and Ni2+ have been achieved on stannic selenoiodate columns. The practical utility of the material has been demonstrated by analyzing the metal ion content of electroplating waste.

Journal Article↗
PubMed2004

Surfactant templated sulfonic acid functionalized silica microspheres as new efficient ion exchangers and electrode modifiers.

Porous sulfonic acid functionalized silica spheres have been prepared by oxidation ofthiol-functionalized mesoporous silica samples obtained by co-condensation of (mercaptopropyl)trimethoxysilane and tetraethoxysilane in the presence ofcetyltrimethylammonium as a template. The physicochemical characteristics of the resulting ion exchangers have been analyzed by various techniques and discussed with respect to the amount of functional groups in the materials. Their ion exchange behavior was then studied from batch experiments (determination of cation exchange capacities) and by electrochemistry at carbon paste electrodes modified with these solids. In particular, ion exchange voltammetry applied to two model electroactive cations, Cu2+ and Ru(NH3)6(3+), has pointed out the key role played by the content of organofunctional groups in the materials (which strongly affects their structure and porosity) on their performance as electrode modifiers for preconcentration of target analytes prior to electrochemical detection.

Journal Article↗
PubMed1981

Comparison of an agarose electrophoresis method and four ion-exchange methods for the measurement of the creatine kinase MB fraction in human serum.

Five CK-MB methods were compared; Corning agarose gel electrophoresis, Worthington CPK Isoenzyme columns, E-C columns, Lancer MB/CPK Isoenzyme, and our own DEAE-cellulose column method. The best precision was obtained with agarose electrophoresis at elevated CK-MB levels. However the agarose electrophoresis method was less sensitive than any of the ion-exchange methods. The detection limit for CK-MB by agarose electrophoresis was variable in the range of 67-17 U/L. A significant bias was shown to exist between the ion-exchange methods and the agarose electrophoresis method. Results by the latter were on the average 4.3, 3.6, 2.7 and 1.4 times greater than CK-MB measurements obtained by the Lancer, E-C, Worthington, and DEAE-cellulose methods, respectively. The bias observed between methods was largely due to the low recoveries of CK-MB activity with the ion-exchange methods; recoveries of 106-122%, 68-78%, 42-44%, 16-19%, and 13-14% were obtained at levels of 18-162 U/L, with the agarose electrophoresis, DEAE-cellulose, Worthington E-C, and Lancer methods, respectively.

Chromatography, Ion Exchange↗
PubMed2005

Ion exchanges in apatites for biomedical application.

The modification of the composition of apatite materials can be made by several processes corresponding to ion exchange reactions which can conveniently be adapted to current coatings and ceramics and are an alternative to setting up of new synthesis methods. In addition to high temperature thermal treatments, which can partly or almost totally replace the monovalent OH- anion of stoichiometric hydroxyapatite by any halogen ion or carbonate, aqueous processes corresponding to dissolution-reprecipitation reactions have also been proposed and used. However, the most interesting possibilities are provided by aqueous ion exchange reactions involving nanocrystalline apatites. These apatites are characterised by the existence on the crystal surface of a hydrated layer of loosely bound mineral ions which can be easily exchanged in solution. This layer offers a possibility to trap mineral ions and possibly active molecules which can modify the apatite properties. Such processes are involved in mineralised tissues and could be used in biomaterials for the release of active mineral species.

Apatites↗
PubMed2004

Performance of ion-exchanger grafted textiles for industrial water treatment in dynamic reactors.

The performance of a special class of grafted textiles in removing metal cations from industrial wastewaters was examined in continuous reactors. The influence of various parameters on the ion exchange process (reactor geometry, inlet metal ion concentration, solution flow rate, concentration and type of reagent, etc.) was studied over the complete service cycle of the exchanger (saturation, desorption, regeneration, rinsing). Dynamic ion exchange characteristics were determined and compared with those of resins under identical operating conditions. Higher efficiency of fibrous ion exchangers compared to analogous resins, was shown at all stages of the service cycle. Results were expressed as a function of breakthrough capacity, exchanger utilisation efficiency, volume of solution treated, eluted metal concentration. The use of different reactor geometries showed two of the many possible applications of grafted textiles in water treatment processes.

Industrial Waste↗