Separation of vanadium isotopes by ion-exchange chromatography

Cation-exchange displacement chromatography of VO2+ was carried out for studying vanadium isotope effects in carboxylate ligand-exchange systems. The heavier isotope 51V was enriched in the carboxylate complex solution. The isotope separation coefficients epsilon(= alpha-1) for 50V/51V were 2.2 x 10(-4) and 2.4 x 10(-4) for citrate and lactate systems at 298 K, respectively. These values are much larger than those obtained in a previous study on the malate system. The existence of binuclear complexes of VO2+ may create the conditions for larger isotope fractionation. From the viewpoint of the process development of isotope separation, the heights equivalent to a theoretical plate of these processes were analyzed and found to be very small in each system due to the homogeneous, small and highly porous resin used. Citrate may be better than the other tested systems for the vanadium isotope separation.     

Separation of nebramycin components by ion-exchange thin-layer chromatography

A thin-layer chromatographic method on chromatoplates coated with Dowex 50 × 8 ion-exchange resin, suitable for the separation of 5 nebramycin components, was developed.     

Separation of hemoglobin variants by ion-exchange chromatography on Monobead resins

Our studies on the separation of hemoglobin variants using Monobead ion exchangers show that these ion exchangers will resolve variants that heretofore could not be resolved. Procedures with these ion exchangers, therefore, extend our ability to detect hemoglobinopathies. Since it is also important to study the physicochemical properties of variants, their isolation is of critical importance to the researcher. The methods described in this report enable variants to be isolated in quantitative amounts so that such studies can be performed. Most isolations can be accomplished within 1 h, under mild conditions with aqueous buffers. Elution gradients can be changed conveniently to optimize resolution of most variants. These methods should serve as a valuable adjunct in studying the structure-function relationship of hemoglobin and other proteins.     

Separation of (203)Pb by ion-exchange chromatography on chelex 100 after production of (203)Pb by the Pb(p, xn)(203)Bi--> EC.beta+ (203)Pb nuclear reaction

Bismuth radioisotopes, produced by 50-MeV proton bombardment of a lead target in a cyclotron, are separated from the lead target material by ion-exchange chromatography on a column containing 5.0 ml of Chelex 100. After a decay period of 24 hr, the (203)Pb formed in situ is eluted from the column and then separated from (200)Tl and (201)Tl on a second ion-exchange column containing 0.5 ml of Chelex 100. Separations are sharp and carrier-free (203)Pb is obtained.     

Separation of bismuth from gram amounts of thallium and silver by cation-exchange chromatography in nitric acid

Traces and small amounts of bismuth can be separated from gram amounts of thallium and silver by successively eluting these elements with 0.3M and 0.6M nitric acid from a column containing 13 ml (3 g) of AG50W-X4, a cation-exchanger (100-200 mesh particle size) with low cross-linking. Bismuth is retained and can be eluted with 0.2M hydrobromic acid containing 20% v/v acetone, leaving many other trace elements absorbed. Elution of thallium is quite sharp, but silver shows a small amount of tailing (less than 1 gmg/ml silver in the eluate) when gram amounts are present, between 20 and 80 mug of silver appearing in the bismuth fraction. Relevant elution curves and results for the analysis of synthetic mixtures containing between 50 mug and 10 mg of bismuth and up to more than 1 g of thallium and silver are presented, as well as results for bismuth in a sample of thallium metal and in Merck thallium(I) carbonate. As little as 0.01 ppm of bismuth can be determined when the separation is combined with electrothermal atomic-absorption spectrometry.     

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).     

Separation of thallium-201 from lead-201 using N-benzylaniline

A procedure is described for the liquid extraction of ingrown²⁰¹Tl from its precursor²⁰¹Pb using N-benzylaniline. The yield for a double extraction averaged 95.9±3.2% for thallium; 2.9±4.2% for lead. Yields for back extraction into acetic acid averaged 93.7±1.5%.     

Separation of butyltin and phenyltin species by ion-exchange chromatography with complexing mobile phases

Summary Butyltin and phenyltin species have been separated by ion-exchange chromatography using silica-based and polymer-based columns. Mobile phases consisted of methanol-water mixtures containing polyfunctional carboxylic acids, which can act as complexing agents for organotin species. The best results were achieved with a system based on a methanol mobile phase containing malic and oxalic acids and a polymer-based column, which allowed the separation of tri- and diorganotin compounds and some resolution between monobutyltin and monophenyltin.     

Chemical separation of thallium from mercury by extraction chromatography

Thallium-201 was obtained by irradiating natural mercury with protons from IPEN's CV-28 Cyclotron. The chemical separation process chosen to separate thallium from mercury was an extraction chromatography technique. It consists on the passage of aqueous solutions (mobile phase), containing the elements that will be separated, through a glass column packed with an inert powder (support) saturated with the extractant (stationary phase).     

Separation of guanidino compounds by means of ion-exchange thin-layer chromatography (author's transl)]

Thirteen guanidino compounds including glycocyamine, glycocyamidine, creatine, creatinine, arginine and guanidinosuccinic acid were chromatographed on thin-layer plates pre-coated with ion-exchange resins. Maximum resolution was obtained on layers of the cation-exchange resin eluted with 0.12 M sodium citrate buffer of pH 5.2, permitting the separation of nine of the thirteen guanidino compounds. Relationships between structure and physiochemical properties and the elution patterns of some selected guanidines were graphically evaluated.