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PubMed2000

Peak shapes in open tubular ion-exchange capillary electrochromatography of inorganic anions.

An experimental study of parameters influencing peak shapes in ion-exchange open tubular (OT) capillary electrochromatography (CEC) was conducted using adsorbed quaternary aminated latex particles as the stationary phase. The combination of separation mechanisms from both capillary electrophoresis and ion-exchange chromatography results in peak broadening in OT-CEC arising from both these techniques. The sources of peak broadening that were considered included the relative electrophoretic mobilities of the eluent co-ion and analyte, and resistance to mass transfer in both the mobile and stationary phases. The parameters investigated were the mobility of the eluent co-ion, column diameter, separation temperature and secondary interactions between the analyte and the stationary phase. The electromigration dispersion was found to influence peak shapes to a minor extent, indicating that chromatographic retention was the dominant source of dispersion. Improving the resistance to mass transfer in the mobile phase by decreasing the capillary diameter improved peak shapes, with symmetrical peaks being obtained in a 25 microm I.D. column. However, an increase in temperature from 25 degrees C to 55 degrees C failed to show any significant improvement. The addition of p-cyanophenol to the mobile phase to suppress secondary interactions with the stationary phase did not result in the expected improvement in efficiency.

Anions↗
PubMed1980

Ion exchange method for rapid determination of alkalinity of water-soluble tea ash containing high levels of manganese.

An ion exchange method to determine the alkalinity of water-soluble tea ash containing high levels of manganese is described. A chromatographic column containing a strong cation exchange resin (20-50 mesh) in Na+ form, with a bed volume of 5 mL is used. The present ion exchange method is compared to pH titrations and also to the official AOAC methods (31.012, 31.015, 31.016). Results with the new method are accurate and precise.

Chromatography, Ion Exchange↗
PubMed1984

Isolation of detergent-extracted Sendai virus proteins by gel-filtration, ion-exchange and reversed-phase high-performance liquid chromatography and the effect on immunological activity.

Virus envelope proteins were isolated from Triton X-100 extracts of purified Sendai virions by gel-filtration, ion-exchange and reversed-phase high-performance liquid chromatography (HPLC). The fusion protein F, the matrix protein M and the tetrameric and dimeric form of the HN protein were isolated by gel-filtration HPLC with a solvent containing 0.1% sodium dodecyl sulphate. HN and F were also isolated by ion-exchange HPLC with 0.1% Triton X-100 in the eluent. Reversed-phase HPLC was performed on a C1 column with acetonitrile as the organic solvent. Especially the F1 and F2 component of the fusion protein F were obtained in pure form. The immunological activity of the proteins after HPLC was determined with an enzyme-linked immunosorbent assay (ELISA). After gel-filtration and ion-exchange HPLC, proteins still reacted with antiserum to the intact virus while proteins purified by reversed-phase HPLC did not react.

Animals↗
PubMed2003

Evolution of ion-exchange: from Moses to the Manhattan Project to modern times.

This article explores the history of ion-exchange from records of desalination in the Old Testament and the writings of Aristotle, to the identification of the phenomenon of ion-exchange by two English agricultural chemists, to the invention of suppressed conductivity by Small et al. [Anal. Chem. 54 (1975) 462]. It then focuses on the characteristics of the gradual and continuous evolution of ion chromatography with suppressed conductivity to its current state, with an emphasis on those discoveries that punctuated or revolutionized this evolution.

Chromatography, Ion Exchange↗
PubMed1979

Estimation of catecholamines in human plasma by ion-exchange chromatography coupled with fluorimetry.

Estimation of catecholamines in human plasma was made by ion-exchange chromatography coupled with fluorimetry. Catecholamines in deproteinized plasma were adsorbed onto Amberlite CG-50 (pH 6.5, buffered with 0.4 M phosphate buffer) and selectively eluted by 0.66 M boric acid. The catecholamine fraction was separated further on a column of Amberlite IRC-50 which was coupled with a device for the automated performance of the trihydroxyindole method (epinephrine and norepinephrine) or the 4-aminobenzoic acid-oxidation method (dopamine). One sample could be analysed within 25 min with either method. The lower detection limits were 0.02 ng for epinephrine and dopamine, and 0.04 ng for norepinephrine. Plasma catecholamine contents of healthy adults at rest were epinephrine 0.07 +/- 0.01 ng/ml (n = 19), norepinephrine 0.27 +/- 0.03 ng/ml (n = 19) and dopamine 0.22 +/- 0.03 ng/ml (n = 26). The procedure of adsorption and elution of the plasma catecholamines by ion-exchange resin was simple, the simplicity contributing to constant recovery. The catecholamine fraction could be analysed without evaporation of the eluate. The analytical column could be used for the analysis of more than 1000 samples before excessive back-pressure developed. Our method of continuous measurement of plasma catecholamine fulfils clinical requirements.

Catecholamines↗
PubMed1983

An ion exchange chromatography and radioimmunoassay procedure for measuring opioid peptides and substance P.

The measurements of peptides of the enkephalin, dynorphin and substance P systems is complicated by the number of possible precursor fragments and degradation products that might cross-react with the antisera. By using an ion-exchanger step before radioimmunoassay we can reduce the possibility that observed peptide levels are due to precursors or metabolites. The ion-exchanger method runs with good recovery and its main advantage is that many samples can be run in parallel. The recovery from the ion-exchanger was similar using two different homogenizing media, whereas the measured endogenous levels of [Met] and [Leu]enkephalin were 3-4 fold higher with 1M acetic acid than when a 1:1 MeOH/HCl mixture was used for tissue extraction.

Acetates↗
PubMed2004

[Ion-exchange chromatographic behavior and characterization of Staphylococcus aureus in exponential phase].

A rapid, simple and sensitive method was developed to characterize S. aureus in exponential phase by a high performance ion-exchange chromatograph equipped with a laser light-scattering detector. An ion-exchange column (TSKgel SuperQ-TOYOPEARL 650C column, 7.6 mm i.d. x 100 mm, Tosoh, Japan) was used for the separation. The mobile phase was a 20 mmol/L piperazine-hydrochloric acid (pH 6.0) buffer. It was found that S. aureus in exponential phase exhibited two elution peaks. Transmission electron microscope (TEM) showed that the bacterial cells in the first peak appeared to be circular, while the cells in the second one appeared to be elliptical and had one obvious diaphragm. It is found that the proliferation capability of the second fraction was better than the first fraction by 65.3%. These results suggested that the first fraction was the S. aureus that stopped dividing, while the second one was the S. aureus that were undergoing cell division. Therefore, the chromatographic method developed here may be a promising tool for the rapid and efficient separation and characterization of bacterial cells.

Animals↗
PubMed2003

Determination of tricarboxylic acid cycle acids and other related substances in cultured mammalian cells by gradient ion-exchange chromatography with suppressed conductivity detection.

An ion-exchange chromatography method was established for simultaneously analyzing the tricarboxylic acid (TCA) cycle acids and other related substances in cultured mammalian cells, including citrate, cis-aconitate, isocitrate, alpha-ketoglutarate, succinate, malate, fumarate, oxaloacetate, trans-aconitate, phosphate, lactate and pyruvate. A Dionex 600 ion chromatograph with an ion suppressor and a conductivity detector, and an IonPac AS11-HC analytical column were employed. An NaOH gradient elution containing 13.5% methanol contributed to sufficient separation of target substances. The stability of carboxylic acids was investigated and oxaloacetate was found to be extremely unstable especially at pH 3. TCA cycle acids and other related substances in Chinese hamster ovary (CHO) cells were separated completely, and lactate, malate, phosphate, citrate and cis-aconitate were quantified due to their higher concentrations. In the quantification of the five substances, detection limits (S/N=3) ranged from 0.12 to 0.48 microM, the correlation coefficients from 0.9982 to 1.0000 in their linear ranges of concentration, and the recoveries from 87 to 95%. The metabolic status of CHO cells was analyzed on the basis of the intracellular concentrations of TCA cycle acids.

Animals↗
PubMed1995

Extraction of serum and urine calcium with ion exchange membrane filters for isotope enrichment determination using thermal ionization mass spectrometry.

The extraction of calcium from water, serum, and urine using Bio-Rex 25 mm ion exchange membrane filters was compared with the oxalate precipitation procedure currently used in our laboratory. Total recoveries of a known quantity of calcium loaded onto the membrane filters for water, serum and urine were as follows: (a) cation exchange filter, 85%, 74%, and 66%; (b) Chelex, 65%, 98%, and 20%; and (c) oxalate precipitation, 93%, 100%, and 96%, respectively. Regression analysis for precipitation versus ion exchange isotope ratio measurements of standards prepared using highly enriched calcium-44 showed slopes of unity. An improvement of automated sample analysis was observed for water and urine calcium samples extracted with ion exchange filters.

Calcium↗
PubMed2005

Preparation and characterization of a novel pH-sensitive ion exchange resin.

Methylacrylic acid/styrene cross-linked with divinylbenzene is a novel pH-sensitive ion exchange resin. Microspheres of this resin were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The microspheres showed a pulsatile swelling behavior when the pH of the media changed. The pH-sensitive microspheres were loaded with salbutamol sulfate and the drug-release characteristics were studied under both simulated gastric and intestinal pH conditions. The results obtained showed that the drug release also depended on the pH of the release media.

Hydrogen-Ion Concentration↗
PubMed2003

Large-scale ion-exchange column chromatography of proteins. Comparison of different formats.

This review describes the performance of various column designs available to process-scale users of low-pressure chromatography for protein purification. By carrying out a range of ion-exchange separations using Whatman microgranular ion-exchange celluloses we are able to compare and contrast the practical performance issues associated with several designs of axial and radial flow columns.

Anion Exchange Resins↗
PubMed1987

Large scale use of Spherosil ion exchangers in plasma fractionation.

Spherosil microbeads are spherical and made of porous silica. Their surface is coated with hydrophilic and/or hydrophobic polymers. They are specially designed for the separation of proteins on an industrial scale either by ion exchange or by bioaffinity chromatography. Since 1980, large columns have been used in Institut Mérieux for the purification of placental albumin and several vaccines. Here we describe a chromatographic process for the purification of human albumin and immunoglobulins (IgG) from 25 1 of plasma per cycle. First the plasma was freed of the coagulation factors and then clarified at pH 5.25. The corresponding supernatant was filtered and processed in sterile conditions. Albumin was then purified by ion exchange on 3 successive columns, respectively containing: 6.25 kg of DEAE SPHEROSIL W-1000; 3.5 kg of QMA SPHEROSIL PH-1000; 8 kg of COOH-SPHEROSIL W-1000. The concentration and pH of the buffers were selected to reduce, as much as possible, the total quantity of ion exchangers required per cycle. IgG were then purified from the filtrate of the first of the previous columns. 1 column of 6.25 kg of DEAE SPHEROSIL W-1000 was used at pH 6.8. The selected chromatographic parameters allowed us to demonstrate a total elimination of HBs Ag and HB Virus when voluntarily added to an initial sample (RIA determination and HBV-DNA analysis by molecular hybridization). A second column of a large pore anion exchanger: DEAE SPHEROSIL LP-3000 was added at the end of the IgG purification, as a final security to avoid any risk of transmitting the Hepatitis B virus. The yield and quality of the final products will be presented.

Chromatography, Gel↗
PubMed2004

Cleaning power and abrasivity of a new toothpaste based on ion-exchange resins.

PURPOSE: To compare the stain removal efficacy and enamel abrasivity of a new experimental dentifrice based on an ion-exchange resin mixture that releases calcium, fluoride, phosphate and zinc ions (named NMTD1), to four commercially available dentifrices: Crest Extra-whitening toothpaste, Crest Tartar Protection toothpaste, Crest Cavity Protection toothpaste and Colgate Fluoride Cavity Protection toothpaste. Calcium pyrophosphate was used as a control for the efficacy of the staining removal experiment. METHODS: Cleaning power evaluation was made following the method developed by Stookey et al. The abrasion of the toothpastes was determined by means of a brushing machine, using 2000, 4000 and 8000 strokes and a 250g toothbrush load. Bovine specimens were prepared and abrasion was measured by a surface profilometer system. RESULTS: The new experimental dentifrice did not remove stains whereas Crest Extra-whitening and Crest Cavity Protection dentifrices produced statistically significant stain removal when compared with the calcium pyrophosphate control. Abrasion studies demonstrated that abrasion was linearly correlated to the number of strokes and the abrasion rates proved to be non significant for Colgate and the new experimental dentifrices, but significant for Crest Extra-whitening, Crest Tartar Protection and Crest Cavity Protection. CLINICAL SIGNIFICANCE: This study demonstrated that the use of a dentifrice based on an ion-exchange mixture was not effective at removing stains and abrasion was most insignificant when compared to other commercially available toothpastes.

Animals↗
PubMed2005

Matrix assisted refolding of proteins by ion exchange chromatography.

Two different approaches of matrix assisted refolding have been evaluated and compared to conventional refolding by dilution. Bovine alpha-lactalbumin was used for the studies as model protein. It was adsorbed under denaturing conditions on an ion exchange matrix and refolding was completed on the column prior to elution or, depending on the buffer system, in the eluate. Agarose based chromatography matrices showed high capacities for the denatured alpha-lactalbumin. A positive effect on the yield of refolded protein by the matrix could be observed for Fractogel EMD DEAE and a negative for Toyopearl DEAE 650M, DEAE Sepharose FF and Q Sepharose FF. In the case of Fractogel EMD DEAE the ion exchange surface might act as a folding helper. This property may be caused by the grafted polymers. For Source 30Q only a marginal negative influence on the refolding kinetics was observed, thus the ion exchanger is only a mean for removal of chaotropic agents. Refolding on the column is characterized by a low yield but high productivity due to significant reduction of refolding time.

Chromatography, High Pressure Liquid↗
PubMed2000

Electrogenerated chemiluminescence of tris (2,2'-bipyridyl)ruthenium(II) ion-exchanged in nafion-silica composite films

The voltammetry and electrogenerated chemiluminescence (ECL) of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3 2+) ion-exchanged in Nafion and Nafion-silica composite materials have been investigated. The major goal of this work was to investigate and develop new materials and immobilization approaches for the fabrication of ECL-based sensors with improved reactivity and long-term stability. Nation-silica composite materials with varying contents of Nation (53-100 wt% relative to silica) were prepared via the two-step acid/base hydrolysis and condensation of tetramethoxysilane. The Nafion doped sols were spin cast on glassy carbon electrodes, dried, and then ion-exchanged with Ru(bpy)3 2+. The shapes of the cyclic voltammetric curves and the amount of Ru(bpy)3 2+ exchanged into the films strongly depends on the amount of Nafion incorporated into the hybrid sol. Nafion-silica films with a low content of Nafion ion-exchanged less Ru(bpy)3 2+ and exhibited tail-shaped voltammetry at 100 mV/s. The ECL of immobilized Ru(bpy)3 2+ in the presence of either tripropylamine or sodium oxalate in pH 5 acetate buffer was also strongly dependent on the amount of Nafion introduced into the composite with greater ECL observed for the Nafion-silica films relative to pure Nafion.

Journal Article↗
PubMed1977

Unstirred layer effects on calculations of the potential difference across an ion exchange membrane.

The potential difference between two solutions of the same 1:1 electrolyte bathing an ion exchange membrane has been calculated as the sum of the following components: (a) a Donnan potential at each membrane-solution interface, (b) a diffusion potential within the membrane phase, and (c) a diffusion potential in the unstirred layer on each side of the membrane. For a highly charged ion exchange membrane with at least one surface in contact with a dilute solution, calculated transmembrane potential differences are extremely sensitive to the assumed thickness of the unstirred layers. This sensitivity to unstirred layer thickness is primarily due to changes in the Donnan components of the potential difference. By this approach, it was possible to fit membrane potential data from Gunn and Curran (1971, Biophys. J. 11:559) for a range of bathing solution concentrations from 0.0016 to 4.0 M. If no effort was made to account for the modification of the Donnan potentials by the presence of unstirred layers, the data appeared incompatible with an electrodiffusion equation description. Suggestions for a more stringent experimental test and a brief discussion of possible implications for electrical measurements on fresh-water giant algal cells are presented.

Diffusion↗
PubMed1977

Solvent-generated ion-exchange systems with anionic surfactants for rapid separations of amino acids.

The retention behaviour of amino acids in phase systems consisting of a hydrophobic solid support as the stationary phase and water-organic solvent mixtures containing a small amount of an anionic detergent as the mobile phase was investigated. Such phase systems are found to behave like conventional ion-exchange systems. The degree and order of retention of amino acids can be influenced by changing the temperature, the nature of the hydrophobic support, the pH and the nature and concentration of the anionic detergent, organic constituent and counter ion in the eluent. In many instances this solvent-generated (dynamic) ion-exchange chromatography shows a greater selectivity than conventional ion-exchange systems towards amino acids. The results obtained so far indicate that a complete separation of the 19 protein amino acids by applying solvent gradients or/and multi-column system is possible within 30 min.

Amino Acids↗