Cation-exchange Resin Column Research Articles

Simple high-performance liquid chromatographic method for the quantitation of 5-fluorouracil in human plasma

A simple, rapid, specific and sensitive high-performance liquid chromatography method has been developed for quantitation of 5-fluorouracil (5-FU) in human plasma. The method involves deproteinization of a small sample volume of plasma (150 μl) followed by HPLC on a cation-exchange resin column, Aminex HPX-87H (300×7.8 mm I.D.), preceded by a similar guard cartridge with UV detection at 265 nm. This method allows a good separation of 5-FU with a retention time of 24 min and a detection limit at 25 ng/ml. The calibration curve was linear from 25 to 2000 ng/ml. The coefficient of variation was ≤4.4% for within-day reproducibility and ≤9.5% for day-to-day reproducibility.

Spectroscopic study of ion binding in synthetic polyelectrolytes using lanthanide ions

Spectroscopic properties of Ln(III) bound to six polyacrylic acids of molecular weights ranging from 2000 to 4 000 000 daltons are described. These complexes were characterized using Nd(III) absorption of the hypersensitive band at π 575 nm and stopped-flow spectroscopy, as well as Eu(III) luminescence lifetime and 5D 0← 7F 0 selective excitation spectra. The luminescence lifetimes of Eu(III), the changes in the absorption of Nd(III) and passage through columns of cation exchange resin gave a predominance of rapid, strong, binding of Eu(III) with about 3% more weakly bound. The variation of intensity of the Eu(III) 5D 0← 7F 0 selective excitation spectra indicates a molar ratio of 1:3 for Eu(III):[COO −] with three residual waters of hydration in the inner coordination sphere of the bound Ln(III). No significant changes in either the hydration number or the excitation spectra have been observed among the Eu/PAA complexes for varying PAA.

Ion Chromatographic Determination of L-Ascorbic Acid, Sulfite, Sulfide and Thiosulfate Using a Cation-Exchanger of Low Crosslinking

L-Ascorbic acid, sulfite, sulfide and thiosulfate have each been completely separated from their mixtures by a single run of ion chromatography using columns of a sulfonated styrenedivinylbenzene copolymeric cation-exchange resin of low crosslinking (1%) and an eluent of 2.3×10-3M (M=mol dm-3) sulfuric acid containing 4%(v/v) acetonitrile. L-Ascorbic acid and sulfite as sulfurous acid were eluted early by an ion-exclusion effect of the cation-exchanger in the hydrogen form, but both the sulfide as hydrogen sulfide and the thiosulfate ion were eluted late, owing to their adsorption onto the resin bed. The sample species in the effluent were monitored by photometric measurement of the excess of iodine (as triiodide) for its postcolumn reaction with each species separated. The chromatograms obtained gave negative peaks, based on the decrease in the absorbance from background. Calibration graphs for the four species, plotted as peak-heights vs. concentrations, were linear up to 3.00×10-5M for L-ascorbic acid, 1.25×10-4M for sulfite, 5.00×10-4M for sulfide and 1.20×10-4M for thiosulfate, respectively. Detection limits as S/N=3 were 1.00×10-7M for L-ascorbic acid, 1.15×10-6M for sulfite, 1.80×10-6M for sulfide and 6.80×10-6M for thiosulfate. The proposed method was successfully applied to the determination of L-ascorbic acid in soft drinks, sulfide in hot-spring waters and sulfite in wines.

Ion-exclusion chromatography with conductimetric detection of aliphatic carboxylic acids on an H +-form cation-exchange resin column by elution with polyols and sugars

The Ion-exclusion chromatography (IEC) of normal aliphatic carboxylic acids of different acidity (p K a) and hydrophobicity was investigated on a poly(styrene-divinylbenzene) (PS-DVB)-based strongly acidic cation-exchange resin column in the H + form and conductimetric detection. When water was used as the eluent, although the C 1-C 5 carboxylic acids were separated from strong acid (HCl) depending on the p K a and the hydrophobicity, the resolution was low and the peaks were accompanied by leading depending on their hydrophobicities. To improve the peak shape and the peak resolution, aqueous eluents of polyols and sugars containing 1–8 alcoholic OH groups (methanol, ethylene glycol, glycerol, erythritol, xylitol, fructose, sorbitol, and sucrose) were tested for the IEC separation of the carboxylic acids. When aqueous eluents of polyols and sugars were used, the tendency for leading peaks was decreased drastically with increasing number of OH groups in the polyols and sugars. This is due mainly to the increase in the hydrophilicity of the PS-DVB surface by the OH groups. An aqueous eluent of 10% methanol-0.15 M sucrose gave a reasonable resolution and highly sensitive detection for carboxylic acids. This eluent has a much lower background conductivity (ca. 4 μS cm −1) and much higher detection sensitivity (ca. 170 times higher for valeric acid) than the 0.5 m M sulfuric acid (ca. 390 μS cm −1) commonly used as an eluent in conventional IEC with conductimetric detection.

Simultaneous ion-exclusion chromatography-cation-exchange chromatography with conductimetric detection of anions and cations in acid rain waters

A simple, selective and sensitive method was investigated for simultaneously determining anions (Cl −, NO 3 −, SO 4 2−) and cations (Na +, NH 4 +, K +, Mg 2+, Ca 2+) in acid rain and related environmental waters in central Japan. The method involves simultaneous ion-exclusion-cation-exchange chromatography with conductimetric detection on a polyacrylate weakly acidic cation-exchange resin column with a weak-acid eluent. With the weak-acid eluent (tartaric acid) both anions and cations were separated simultaneously, based on ion-exclusion and cation-exchange mechanism. Owing to the presence of H + ions in the tartaric acid eluent, the detector response was positive for the anions and negative for the cations. Using a 5 m M tartaric acid-7.5% methanol-water eluent, good simultaneous separation and detection were achieved in about 30 min. The results indicated an ionic balance of about 100% between the anions (including HCO 3 −) and the cations (including H +).

Determination of biogenic amines in leafy vegetables by amino acid analyser.

An automated ion-exchange chromatographic method is described for determination of biogenic amines in leafy vegetables using a cation-exchange resin column in potassium form and a three-buffer system. The following amines were separated and quantified for Chinese cabbage, endive, iceberg lettuce and radiocchio: putrescine, histamine, cadaverine, spermidine, agmatine, spermine, tyramine. Amines from vegetable samples were extracted with 10% trichloroacetic acid. The total concentration of these amines ranged from 14 to 20 micrograms/g fresh weight. Spermidine was the major polyamine detected, present at concentrations of 7-15 micrograms/g fresh weight.

Isolation and high-performance liquid chromatographic analysis of thearubigin fractions from black tea

Fractions consisting of black tea pigments were isolated and analysed by reversed-phase HPLC. The fractions were shown to be mixtures of the same pigments that had been observed previously, on the HPLC chromatograms of black tea liquor. The thearubigin fractions isolated by Roberts (Roberts' SI and SII thearubigins) were shown to be mixtures of pigments previously classified as group I, II, and III pigments (pigments excluded from, resolved by, and remaining unresolved by HPLC, respectively), showing that the pigments in these three groups were similar to those in groups previously designated as thearubigins by Roberts. The SI and SII fractions were distinguishable by HPLC, and SI-like and SII-like fractions could be isolated by methods different from those of Roberts ( e.g., a Sep-Pak C 18 cartridge). Fractions enriched in group I pigments were isolated using a Bond-Elut SCX cation-exchange cartridge (and on a larger scale on a column of Amberlite CG-120 cation-exchange resin). These fractions were shown by paper chromatography and HPLC to be mixtures of “anthocyanidin” pigments of various molecular masses. HPLC and mass spectrometry showed that an anthocyanidin, designated by Roberts as tricetinidin, was present in the mixture.

Flow-Injection Spectrophotometric Determination of Micro Amounts of Sulfate Ion in Surface- and Sea-Water Samples with a Barium Chromate Reaction Column

A rapid and simple flow-injection method using a reaction column packed with barium chromate powder is described for the determination of micro amounts of sulfate ion in surface- and sea-water samples. An aqueous solution containing 4.5mM sodium acetate and 4% ethanol was used as a carrier solution at a flow rate of 0.8ml/min. The absorbance of the chromate ion (which corresponds to the sulfate ion concentration) in the carrier solution from the reaction column was measured using a photometric detector at 370nm. Interference from some cations was eliminated by the use of a cation-exchange resin column installed in front of the reaction column; interference from some anions was reduced by using the carrier solution mentioned above. The concentration range from 0.5 to 5ppm of the sulfate ion in practical water samples can be determined by the proposed method with good reproducibility.

Recovery of saxitoxin from solution by coprecipitation with hydrated iron(III) oxide

Hydrated iron(III) oxide has been widely used for the concentration of trace amounts of metal ions from aqueous solutions, including sea-water. In this study, the negatively-charged carrier was used to recover saxitoxin, one of a group of highly toxic paralytic shellfish poisons (PSPs), from aqueous solution as a monovalent cation. Although the recovery was not quantitative (65%), it has been demonstrated that coprecipitation can be used to recover saxitoxin, and probably other suitably charged toxins, from solution. As such, the procedure is less tedious than those currently involving the passage of PSP-containing solutions through columns of weak cation-exchange resin, and gel-filtration media.

1H-NMR study on ganglioside amide protons: evidence that the deuterium exchange kinetics are affected by the preparation of samples

The kinetics of H/2H chemical exchange of the amide proton has been suggested as one of the tools available for investigating hydrogenbond stabilizing interactions in gangliosides. The amide proton/deuterium (NH/2H) exchange rates in GM2 ganglioside were studied by 1H-NMR spectroscopy on 12 samples prepared following different procedures. In samples passed through a sodium salt Chelex-100 cation exchange resin column prior to being analysed the N-acetylneuraminic acid NH exchange occurred in less than 10 min and that of ceramide NH in 30 min. The N-acetylgalactosamine acetamido NH exchange was slower, the half-life of the signal ranging from 15 min to 3.5 h. Contact of the Chelex-treated GM2 samples with water, through a dialysis process, modified the NH/2H exchange rate values, the N-acetylgalactosamine acetamido NH exchange becoming faster than that of ceramide NH and similar to that of N-acetylneuraminic acid NH. Our results indicate that the deuterium/proton exchange rate strongly depends on sample preparation (ion content and minor contaminants present in water). The three-dimensional model involving the N-acetylgalactosamine acetamido NH and the N-acetylneuraminic acid carboxyl group hydrogen-bonding, which is supported by experimental evidence, cannot be confirmed by NH-exchange measurement.

Preparation and characterization of two geometrical isomers of the aqua(ethylenediamine- N,N,N′-tri-3-propionatopropionic acid)chromium(III) complex: X-ray structure of cis-eq-[Cr(Hedtp)(H 2O)]·5H 2O

Two geometrical isomers for [Cr(Hedtp)(H 2O)] (Hedtp=ethylenediamine- N,N,N′-tri-3-propionatepropionic acid) were obtained from the most stable diastereoisomer of [Cr(edtp)] − (edtp=ethylenediamine- N,N,N′,N′-tetra-3- propionate) by passing through a column of cation-exchange resin in the H + form. The geometrical structure of one isomer ( H-1) was found to be cis-eq by using the X-ray diffraction method. Crystal data for cis-eq- [Cr(Hedtp)(H 2O]·5H 2O are monoclinic with space group P2 1/ c: a=9.796(6), b=15.195(6), c=14.825(2) Å, β=94.70(4)° and Z=4. The geometrical structure of another isomer ( H-2) was assigned to trans-eq on the basis of the 2H NMR and the magnetic circular dichroism (MCD) spectra.

Column liquid chromatographic determination of sucrose and fructose with use of an enzyme reactor and spectrofluorimetric detection

Immobilized sorbitol dehydrogenase was used as a reactor in a column liquid chromatographic system for the selective detection of sucrose and fructose. Sorbitol dehydrogenase was immobilized on controlled-pore glass. The sugars were separated on a cation-exchange resin column with a mobile phase containing 0.1 M phosphate buffer (pH 7.0) and 100 μM NADH. The disappearance of NADH was detected spectrofluorimetrically. For sucrose the linear working range was 50–500 μM, with a detection limit of 10 μM (170 ng in a 50-μl injection); for fructose the range was 25–250 μM, with a detection limit of 5 μM (45 ng in a 50μl injection).

Comparison of cation-exchange and chelating cation-exchange resins for the concentration of saxitoxin

Current methods for the concentration of paralytic shellfish poisons involve passage of an extract solution through a column of cation-exchange resin, followed by elution and subsequent passage through a column of size-exclusion medium. Although effective, such procedures are tedious and time consuming. The results of a study comparing the characteristics of a cation-exchange resin with a chelating cation-exchange resin indicate that the latter is selective towards saxitoxin (the most important and most studied of the toxins). In addition, the chelating cation-exchange resin has faster kinetics for abstraction of saxitoxin from solution than does the cation-exchange resin. These features recommend chelating cation exchange for the initial separation of saxitoxin followed by concentration and separation of additional toxins by the normal procedure.

Carbohydrate separation by ligand-exchange liquid chromatography: Correlation between the formation of sugar-cation complexes and the elution order

Carbohydrate separation (hexoses, pentoses and corresponding polyols) was studied by liquid chromatography using ligand exchange on cation-exchange resin column with water as eluent. Seven cations (Ca 2+, Sr 2+, Ba 2+, Pb 2+, Y 3+, La 3+ and Pr 3+) were tested. The carbohydrate elution order is considered in connection with the complexing sites likely to be involved for each sugar or polyol molecule and with the exclusion processes.

Catalytic Spectrophotometric Determination of Traces of Molybdenum (VI)

Abstract The catalytic effect of molybdenum on the reduction of Nile blue by hydrazine is utilized. The method is based on measuring the decrease in absorbance of Nile blue after the fixed time of 3 min at 595 nm at 25°C. The interferences of various ions were studied and a cation-exchange resin column was used to remove interfering ions. Five replicate analyses of a sample containing 3 μ g.ml−1 of molybdenum had a relative standard deviation of 0.67%. The method enables rapid and reliable analysis of molybdenum over the concentration range of 40–3000 ng.ml−1 in different samples.

Size fractionation of oligosaccharides by liquid chromatography on a cation-exchange column

Oligosaccharides, labelled with 2-aminopyridine at their reducing ends, were satisfactorily fractionated according to the sugar sizes on Shodex RSpak DC-613, a cation-exchange resin column (Na + form), with water-acetonitrile as the eluent in the presence of sodium acetate or triethylammonium acetate buffer. For the fractionation of sufar samples, dextran hydrolyzates, chitin oligomers and oligosaccharide moieties of ovomucoid were used. The oligosaccharides were strongly adsorbed to the resin column with solvents containing less water and at lower temperature, and were eluted in order to increasing molecular size above the critical concentration of acetonitrile. Baseline separation of a dextran hydrolyzate up to oligomers having 20 glucose units was observed by gradient elution. The separation efficiency and elution pattern were investigated by changing the buffer concentration, mobile phase pH and temperature.

Breakthrough Curve of Lysine on a Column of a Strong Cation-Exchange Resin of the Ammonium Form

Abstract By using a “finite-segment” model for an ion-exchange column, breakthrough curves of ternary cation components—lysine, ammonium, and hydrogen—on a column of a cation-exchange resin of the ammonium form are calculated as a function of limited parameters such as the selectivity coefficients and the dissociation constant of the amino acid. Experimental breakthrough curves on a fixed column packed with Diaion SK-IB (nominal DVB 8%) are simulated and analyzed by the calculated results. Within a limited flow rate of the liquid phase, the model is valid for experimental results, including dependencies on the pH and the ratio of lysine to ammonium, when the conditions of electroneutrality are obeyed.

PREDICTION OF RETENTION TIME FOR GRADIENT ELUTION USING STEPWISE ELUTION EQUATION

Prediction of retention tines for gradient elution of inorganic ions was tried out using the stepwise elution equation. Retention the for some inorganic anions was isocratically measured with NaOH eluent on the anion exchange resin column. The slope frog a plot of log k' against log [OH-] was obtained by a linear regression. The calculated k' was applied to predict retention time of each inorganic anion for a gradient elution. Retention tine of lanthanides was measured using α-HiBA and mandelic acid as a complexing agent on the cation exchange resin column. Capacity factor for each metal-ligand complex was obtained frog the measured k' by non-linear regression. The same calculation was performed on the retention time of metal ions for gradient elution.

Column liquid chromatographic determination of saccharides with a single calibration graph using post-column enzyme reactors and coulometric detection

Immobilized enzymes were used as column reactors in a column liquid chromatographic system for the specific detection of the saccharides stachyose, raffinose and sucrose. Invertase and fructose dehydrogenase (FDH) were immobilized onto poly(vinyl alcohol) beads and porous glass beads, respectively. The oligosaccharides were separated on a cation-exchange resin column with water as the mobile phase. Invertase was capable of quantitatively hydrolysing the oligosaccharides to fructose, which reacts with the hexacyanoferrate(III) ion in the presence of FDH. The hexacyanoferrate(II) ion produced was monitored coulometrically. A single calibration graph for fructose based on the peak area was used to determine each oligosaccharide. The limits of detection for stachyose, raffinose and sucrose were 27, 5 and 2 ng (in a 50 μl sample), respectively.

Ion exchange separation of trace amounts of uranium and thorium in tantalum for neutron activation analysis

Separation method of a few ppb of uranium and thorium in tantalum metal by ion exchange for neutron activation analysis was established. After dissolving tantalum metal by hydrofluoric acid, uranium and thorium were separated from tantalum using cation exchange resin column in 0.5M hydrofluoric −0.65M boric acid media. Both of the yields for uranium and thorium during separation were above 95% and the remaining amount of tantalum be lowered below 400 ng.