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PubMed1972

Recovery of steroidal glucosiduronic acids from organic solvents containing anionic liquid ion-exchangers.

Solutions of anionic liquid ion-exchangers in organic solvents are potentially useful for extracting steroidal glucosiduronic acids from biological fluids and for purifying mixtures of these acids by chromatography. If a glucosiduronic acid is to be isolated in pure form after either of these procedures, it is necessary to separate it from the ion-exchanger. Separation from an organic solution of tetraheptylammonium chloride may be accomplished by extraction with water under the following conditions, which promote transfer of a glucosiduronate to the aqueous phase: (1) an appropriate solvent (diluent) as the organic phase, (2) the presence in the two-phase mixture of an anion such as myristate or dodecyl sulphate to combine with the tetraheptylammonium ion, and (3) an increase of the pH of the aqueous phase in association with the presence of myristate or dodecyl sulphate. The foregoing factors apply also to removal of glucosiduronates from organic solutions of ion exchangers that are hydrochlorides of tertiary, secondary, or primary amines. Since these amines exert progressively less solubilizing effect for glucosiduronates as the pH of the aqueous phase is increased, the conjugates can be released from the organic phase by adjusting the pH to 10 and omitting the myristate or dodecyl sulphate.

Amines↗
PubMed2001

Improvement of strength parameters of a leucite-reinforced glass ceramic by dual-ion exchange.

An innovative dual ion-exchange process can improve the limited strength and the scatter-in-strength of technical glasses. The objective of this study was to prove whether such a two-stage ion-exchange process can also improve the limited strength and the problematic scatter-in-strength of dental ceramic materials. The first exchange was done in KNO3 on a leucite-reinforced glass-ceramic material, the second exchange in 70 mol% KNO3, 30 mol% Na NO3 at different treatment times and temperatures. The dual-exchange process approximately doubled the Weibull strength. Moreover, the Weibull modulus showed a four-fold increase, i.e., the coefficients of variation were reduced from 18.3 to 4.7%. We conclude that the dual-exchange process may help significantly to increase the clinical reliability of glass-ceramic dental restorations, because the strength and the scatter-in-strength will be substantially improved by this treatment.

Aluminum Silicates↗
PubMed1990

Separation processes in biotechnology. Ion-exchange processes.

Through the use of several differentiating mechanisms, ion exchangers can separate ionic and nonionic materials, solutions containing only ionic species, and even completely nonionic mixtures. Although the mechanisms are distinct in their mode of operation, the resin characteristics that influence the results are largely the same. A practical understanding of the resin properties involved is all that is necessary to begin to use ion-exchange resins successfully. Ion exchange owes most of its history to water treatment, which has provided the economic and technological driving force in the past for the development of improved resins. However, specialty applications such as those in biotechnology are steadily becoming major factors in industry, perhaps not in shear volumes of resin used, but certainly in the value added by the process. The field of biotechnology no doubt holds many of the exciting new applications for ion exchange.

Adsorption↗
PubMed1990

Determination of creatinine in serum by high-performance liquid chromatography: a comparison of three ion-exchange methods.

Three ion-exchange high-performance liquid chromatographic methods for the determination of creatinine in serum have been compared. In method 1 a strong cation exchanger was used. In method 2 a reversed-phase column was given strong cation-exchange properties by the addition of N-methyloleoyl taurate to the mobile phase. In method 3 a weak cation exchanger was used. Elution was with a pH gradient in methods 1 and 2, and isocratic elution was used in method 3. The imprecision was similar for the three methods and varied between 0.9 and 2.5% as studied within-day and between 1.4 and 3.2% from day-to-day. The lowest coefficient of variation was obtained around the upper reference limit. Analytical recoveries were quantitative for the three methods. The method with N-methyloleoyl taurate showed no advantages over the conventional strong cation exchanger. With the weak cation exchanger no interferences were detected from compounds investigated, but with the strong cation exchanger a slight interference was obtained with uric acid. We prefer the weak cation-exchange method because of its simplicity, higher throughput and absence of interference from hitherto tested compounds.

Cation Exchange Resins↗
PubMed1989

[Ion exchange interactions on silica gel layers. II. Halogen salts of compounds containing organic tertiary and quaternary nitrogen].

Primary and secondary ion exchanges--of hydrochloric acid and hydrobromic acid salts of well hydrolyzing organic bases as well as quaternary ammonium bromide which are important drug substance--taking place on silica gel using methanol as mobile phase have been investigated by thin-layer chromatographic and spectrophotometric methods. In case of tertiary ammonium salts (hydrolyzing salts) basis linked to silanate ion and halogen acid have been formed by primary ion exchange. During secondary ion exchange halogen acid has exchanged metal ions linked to silanate ions on the layer. In case of non hydrolyzing salts, the quaternary ammonium bromide salts it could not surely be proved by the applied methods whether primary ion exchange had been followed by secondary ion exchange or only primary ion exchange had occurred.

Amines↗
PubMed2002

Microwave-assisted simple ion-exchange of ZSM-5-type zeolites with copper ions and their specific adsorption properties for N2 molecules at room temperature.

Copper ion-exchanged ZSM-5 samples, prepared using an easy method that takes advantage of microwaves, exhibit a quite peculiar adsorption feature for dinitrogen molecules, in that a large volume of chemisorbed N2 was detected, even at room temperature, and the specificity of the adsorption properties was clarified by comparing with the properties of samples prepared by an ordinary ion-exchange method.

Adsorption↗
PubMed1999

Manipulation of separation selectivity for alkali metals and ammonium in ion-exchange capillary electrochromatography using a suspension of cation exchange particles in the electrolyte as a pseudostationary phase.

The viability of using ion-exchange particles as a pseudostationary phase in capillary electrochromatography for the separation of monovalent inorganic cations has been investigated. Using sulfonated polymeric particles (average diameter 225 nm) as the pseudostationary phase, the separation selectivity for alkali metals and ammonium was examined under a range of background electrolyte compositions and employing indirect absorbance detection. Addition of ion-exchange particles to the background electrolyte resulted in a reduction in the observed electrophoretic mobility of the analytes due to the establishment of ion-exchange interaction with the pseudostationary phase, with the decrease in mobilities following the ion-exchange interaction order for these analytes with a sulfonated stationary phase. Increasing the concentration of the particles resulted in a uniform reduction in the electrophoretic mobility of the analytes, similar to that observed in micellar electrokinetic chromatography. Conversely, increasing the concentration of the cationic indirect detection probe (which also acted as an ion-exchange competing cation) resulted in a decrease in the ion-exchange interaction with the particles and a reduction of the relative ion-exchange contribution to the overall separation mechanism. Plots of log[retention factor] versus log[electrolyte concentration] were linear, as is the case for ion-exchange chromatography, but the observed slopes were greater than predicted from ion-exchange theory. Indirect absorbance detection was found to give poor sensitivity due to light scattering effects caused by the particles of pseudostationary phase.

Cations↗
PubMedDate not supplied

[Ion-exchange properties of immobilized DNA: influence of the polymer concentration and the solvent nature on the exchange of alkali metals].

The method of ion exchange on immobilized DNA, which allows to determine quantitative parameters of ion binding with a high precision, is used for studying of DNA ion selectivity. Insoluble ion exchangers on the DNA basis with the exchange capacity of 0.09 and 0.17 mg-equiv. per 1 g of dry gel are synthesized by means of immobilization of DNA gel in polyacrylamide gel. Constants of ion-exchange equilibrium for the exchanges K+-Na+ and K+-Li+ are determined on these exchangers in water and 50% water-dioxane solution. It is shown that DNA binds selectively only Li+. The selectivity to Li+ increases with the increase of DNA concentration in gel. The specific properties of Li+-DNA in solutions and in the solid state, for example, the impossibility of the B-A transition, are discussed. The selectivity reversal in favor of K+ is observed in water-dioxane solution. The cause of the selectivity reversal and the question of possible participation of cell polyelectrolytes in creation of ion gradients in the living cell are discussed.

Animals↗
PubMed2002

Effects of antihypertensive therapy on cardiac sodium/hydrogen ion exchanger activity and hypertrophy in spontaneously hypertensive rats.

BACKGROUND: Sodium/hydrogen ion exchange is hyperactive in hypertension. Myocardial sodium/hydrogen ion exchange hyperactivity accompanies the regression of cardiac hypertrophy in spontaneously hypertensive rats (SHR) after long term control of blood pressure with enalapril. OBJECTIVES: To explore whether this effect is shared by other antihypertensive agents or is specific to angiotensin-converting enzyme inhibition. ANIMALS AND METHODS: SHR and normotensive Wistar Kyoto (WKY) rats were treated for five weeks with enalapril (20 mg/kg/day), nifedipine (10 mg/kg/day) or losartan (40 mg/kg/day). Sodium/hydrogen ion exchange activity was estimated in terms of both steady intracellular pH in HEPES buffer and the rate of intracellular pH recovery from intracellular acid loads in isolated superfused 2'-7'-bis(2-carboxyethyl)-5,-(and-6)-carboxyfluorescein, acetoxymethyl ester form-loaded papillary muscles. RESULTS: Enalapril, nifedipine and losartan decreased systolic blood pressure in SHR to about the same value (140 3, 140 2 and 146 3 mmHg, respectively, at the end the treatment). However, the index of cardiac hypertrophy (heart weight to body weight ratio) was decreased to a smaller value with losartan than with nifedipine or enalapril (2.66 0.09, 3.06 0.05 and 2.86 0.04 mg/g respectively; P<0.05 ANOVA). For the untreated SHR, the index of cardiac hypertrophy was 3.30 0.04 mg/g. Myocardial sodium/hydrogen ion exchange hyperactivity in SHR was normalized by all treatments. CONCLUSIONS: The three treatments regressed cardiac hypertrophy and normalized sodium/hydrogen ion exchange exchange activity in SHR, and losartan was the most effective treatment for reversing cardiac hypertrophy, despite producing effects on blood pressure and sodium/hydrogen exchange activity similar to that of other antihypertensive drugs.

Animals↗
PubMed2001

Applicability of Simplified Models for the Estimation of Ion Exchange Diffusion Coefficients in Zeolites.

The applicability of simplified models for the determination of ion exchange diffusion coefficients in zeolites is examined. The simplified models examined are Vermeulen's, Paterson's, and Nernst-Plank's approximations for isotopic and ion exchange processes, used in ion exchange systems analysis. Parameter analysis indicates the limits for fractional attainment of equilibrium U(t), the ratio of exchangeable ions in liquid to solid phase (w), and the ratio of surface diffusion coefficients of exchangeable ions (a), all clearly inter-related, within which the above-mentioned simplified models can be successfully used. Studies of the applicability of the isotopic exchange simplified models to experimental data for batch-type Na(+)-Pb(2+) exchange on clinoptilolite confirm the parameter analysis conducted. Copyright 2001 Academic Press.

Journal Article↗
PubMed2003

Ion-exchange properties of colloidal particle consisting of polyaniline and poly(vinyl alcohol) fixed on silica-gel powder.

A colloidal powder was prepared by fixing polyaniline (PANI, conducting polymer), poly(vinyl alcohol) (PVA, surfactant stabilizer) and a suitable dopant anion to silica-gel powder. This hydrophilic composite colloidal particle incorporates anions with the protonation of PANI in an acidic solution. The anion can be exchanged with other anions when the colloid is immersed in an acidic solution. Thus, the PANI colloid works as an ion exchanger. The ion-exchange properties on the composite colloidal powder were investigated. Anions were successfully and easily exchanged in the order Br- < Cl- < NO3- < ClO4- < SCN-. This ion-exchange selectivity corresponds largely to the ion-exchange equilibrium constants, which are based on a hydrophobic interaction between the anion and colloid. However, this ion-exchange selectivity does not agree simply with the lipophilic order, but is instead explainable by a gap in the effective ion-exchange capacity due to a size effect between the micropore on the colloidal particle formed by the dopant anion in polymerization and anion sizes in the hydrophobic environment.

Journal Article↗
PubMed1976

Quantitative determination of hexosamines in glycoprotein by ion-exchange chromatography.

An ion-exchange chromatographic method for the quantitative determination of glucosamine and galactosamine in glycoproteins is described. The hexosamines are completely separated from interfering peptides of the acid hydrolysate using a small column of cation exchanger in a manner described earlier by Boas. Chromatographic separation of the hexosamine fraction and the determination of glucosamine and galactosamine are accomplished on an amino acid analyzer with ninhydrin.

Chromatography, Ion Exchange↗
PubMedDate not supplied

Zeolitic ammonium ion exchange for portable hemodialysis dialysate regeneration.

Ammonia removal from a recirculating dialysate stream is a major challenge in developing a truly portable, regenerable hemodialysis system. Three zeolites, type F, type W, and clinoptilolite, were found to have good ammonia ion exchange capacity with linear equilibrium ion exchange coefficients of 0.908, 0.488, and 0.075 L/g, respectively. The linear equilibrium ion exchange coefficient relates dialysate ammonia concentration (mumol/L) to the amount of ammonia absorbed by zeolite (mumol/g) at equilibrium. Ammonia uptake by zeolite powders was fast, with equilibrium reached within 15 sec. Zeolite ammonia ion exchange and regeneration through multiple cycles was studied using an ion exchange column containing clinoptilolite pellets. Zeolite ion exchange capability was regenerated by flushing the column with 2 mol/L sodium chloride after an ion exchange run. The column maintained ammonia ion exchange capacity through six ion exchange/regeneration cycles, demonstrating multiple dialysis use possibilities. Atomic absorption spectroscopy of the column effluent showed no detectible (< 1 part per million) Si or Al leached from the zeolite.

Ammonia↗
PubMed2001

Separation of organotin compounds by ion-exchange chromatography and their determination by inverse voltammetry.

An ion exchange procedure was developed for the enrichment, separation and quantification of butyltin and phenyltin species, which show very close half wave potentials by their voltammetric determination. As a case study the separation of dibutyltin (DBT) from triphenyltin (TPT) was investigated. Among different ion exchangers tested, the strong acid ion exchanger PUROLITE C100H, used for industrial purposes, was found to be the most suitable. By using a resin bed volume of 25 mL, a flow rate of the feed solution of 1 mL/min and 3 M HCl in methanol as eluent with a flow rate of 0.5 mL/min, a recovery rate of each species of about 80% could be achieved. The detection limit for the determination of DBT and TPT by anodic stripping voltammetry after their separation and enrichment by the above mentioned ion exchange procedure was found to be 0.4 ng/mL for DBT and 6 ng/mL for TPT in the feed solution, respectively. The applicability of the whole procedure was tested on a sediment candidate reference material of BCR (Bureau of Reference Community).

Chromatography, Ion Exchange↗
PubMed1979

Preparation and evaluation of microencapsulated ion-exchange resin beads.

Ion-exchange resin beads in the benzoate form were coated by several microencapsulation techniques to alter and improve characteristics, especially the control of drug release, of this type of drug delivery system. The most successful techniques included polymer-polymer interaction, temperature change, and nonsolvent addition. The microencapsulated beads then were studied with respect to the release rate of the organic anion to determine the effects of microencapsulation. The release rate of the organic anion could be controlled over a wide range, depending on the encapsulating material characteristics. Factors affecting the extent and rate of release as result of microencapsulation are discussed.

Benzoates↗
PubMed1988

Cationic radioisotope delivery to loose connective tissue in vivo using ion-exchange resin beads.

Ion-exchange resin beads, implanted into connective tissue, were used as the vehicle for the delivery of radiolabelled cations to determine the local distribution of lead, silver and cadmium in loose connective tissue. The system was devoid of systemic toxicity, permitted a predictable release, enabled location of released cations in respect to the site of bead implantation, afforded safety and could be used with several other cations. The radiolabels released into the tissue formed an immediate relationship with inflammatory cells and a more protracted relationship with the matrix elements of the local connective tissue. The lesion induced by the presence of the bead was complicated by the particular cation.

Animals↗
PubMed1987

Evaluation of vaginal malodor and efficacy of treatment by high performance ion exchange chromatography.

High performance ion exchange chromatography was employed to evaluate the presence of short chain organic acids in the vaginal fluid of a woman troubled by persistent foul vaginal odor, but who did not have typical bacterial vaginosis. The vaginal secretions from this patient were collected on a weighed cotton swab and eluted into water and extracted by acidified ether. Salts of the acids were back-extracted into aqueous solution and chromatographed on an H-form resin column and compared to commercially available standards. A strikingly large amount of caproic acid was found. The caproic acid disappeared after metronidazole therapy, and a subsequent follow-up chromatogram showed a predominance of lactic acid. The success of this technique in evaluating the present case suggests that such a method may prove useful in other types of vaginal infection.

Adult↗