Separation by ion-exchange

The use of larger particles in the cyclotron, for example carbon, nitrogen or oxygen ions, enabled elements of several units of atomic number beyond uranium to be synthesised. Einsteinium and fermium were obtained by this method and separated by ion-exchange. and indeed first identified by the appearance of their concentration peaks on the elution graph at the places expected for atomic numbers 99 and 100. The concentrations available when this was done were measured not in gcm but in atoms cm. The same elements became available in greater quantity when the first hydrogen bomb was exploded, when they were found in the fission products. Element 101, mendelevium, was made by a-particle bombardment of einsteinium, and nobelium (102) by fusion of curium and the carbon-13 isotope. 

The lanthanides form many compounds with organic ligands. Some of these compounds ate water-soluble, others oil-soluble. Water-soluble compounds have been used extensively for rare-earth separation by ion exchange (qv), for example, complexes form with citric acid, ethylenediaminetetraacetic acid (EDTA), and hydroxyethylethylenediaminetriacetic acid (HEEDTA) (see Chelating agents). The complex formation is pH-dependent. Oil-soluble compounds ate used extensively in the industrial separation of rate earths by tiquid—tiquid extraction. The preferred extractants ate catboxyhc acids, otganophosphoms acids and esters, and tetraaLkylammonium salts. 

Corticotropin [92307-52-3] polypeptide Mr -4697. Extract separated by ion-exchange on CM-cellulose, desalted, evapd and lyophilised. Then run on gel filtration (Sephadex G-50) [Lande et al. Biochemical Preparations 13 45 1971 Esch et al. Biochem Biophys Res Commun 122 899 1984],... 

Proteoglycans (from cultured human muscle cells). Separated by ion-exchange HPLC using a Biogel TSK-DEAE 5-PW analytical column. [Harper et al. Anal Biochem 159 150 1986.]... 

The extent to which one ion is absorbed in preference to another is of fundamental importance it will determine the readiness with which two or more substances, which form ions of like charge, can be separated by ion exchange and also the ease with which the ions can subsequently be removed from the resin. The factors determining the distribution of inorganic ions between an ion exchange resin and a solution include ... 

This sample preparation involves the decomposition of the fungicide (sodium hydroxymethylglycinate) into sodium glycinate and represents the type of sample that requires significant modification before it can be chromatographed. After decomposition it is then separated by ion exchange chromatography. 

The complex has been separated by ion exchange and characterised by direct analysis . The complex has a distinctive absorption spectrum (Fig. 11), quite unlike that of Np(V) and Cr(III). The rate coefficient for the first-order decomposition of the complex is 2.32 x 10 sec at 25 °C in 1.0 M HCIO. Sullivan has obtained a value for the equilibrium constant of the complex, K = [Np(V) Cr(III)]/[Np(V)][Cr(III)], of 2.62 + 0.48 at 25 °C by spectrophotometric experiments. The associated thermodynamic functions are AH = —3.3 kcal. mole" and AS = —9.0 cal.deg . mole . The rates of decay and aquation of the complex, measured at 992 m/t, were investigated in detail. The same complex is formed when Np(VI) is reduced by Cr(II), and it is concluded that the latter reaction proceeds through both inner- and outer-sphere paths. It is noteworthy that the substitution-inert Rh(lII), like Cr(III), forms a complex with Np(V) °. This bright-yellow Np(V) Rh(III) dimer has been separated by ion-exchange... 

It would be easier to describe those classes of compounds not normally separated by RPLC than to catalogue the applications to which RPLC has been turned. Applications for reversed phase can be found in virtually every area of analysis and are reviewed regularly in the journal Analytical Chemistry. RPLC has not been in general use for the analysis of inorganic ions, which are readily separated by ion exchange chromatography polysaccharides, which tend to be too hydrophilic to separate by RPLC polynucleotides, which tend to adsorb irreversibly to the reversed phase packing and compounds which are so hydrophobic that reversed phase offers little selectivity. 

Sadain, S. K. and Koropchak, J. A., Condensation nucleation light scattering detection for biogenic amines separated by ion-exchange chromatography, /. Chromatogr. A, 844, 111, 1999. 

Liquid Chromatography. - Diasteriomeric phosphonodipeptides have been separated by ion exchange column chromatography.267 H.p.l.c. has been used for the analysis of a variety of biologically active phosphorus compounds, such as aminoacid phosphate esters,26 phosphinothrycin,269 inositol triphosphate,270 fructose diphosphate,271 pyridoxal phosphate,272 and ATP.273... 

Ionic solutes can be separated by ion-exchange chromatography using microparticulate resins or bonded ion-exchangers based on microparticulate silica. Such separations are often achieved more easily by ion-suppression or ion-pairing techniques, which use bonded phase columns in the reverse phase mode. 

Oligonucleotides have also been separated by ion-exchange chromatography of yeast ribonucleic acid treated either with acid216 or with ribonuclease.209 Alkaline hydrolysis of the fission products obtained with the latter gives rise to pyrimidine nucleoside 3-phosphates and mixtures of purine nucleoside 2- and 3-phosphates. Bone phosphomonoesterase196 followed by alkaline hydrolysis gives pyrimidine nucleosides and purine... 

Maher [13] has described a procedure for the determination of inorganic arsenic, monomethylarsenic and dimethylarsenic in marine organisms and estuarine sediments. The arsenic species are isolated by solvent extraction, separated by ion-exchange chromatography and selectively determined by arsine generation. Recoveries of spikes of 5 and lOpg of arsenic taken through the whole procedure were 92-96%. 

Ion-pair liquid chromatography can be applied to compounds separated by ion-exchange liquid chromatography, and mixtures of ionic and non-ionic compounds are easily separated. The latter separation is difficult by ion-exchange liquid chromatography. Anions can be separated by reversed-phase ion-pair liquid chromatography (Figure 4.18). 

Reaction 4 in Table 5.1, on the other hand, was one of the first-established examples of an inner-sphere redox reaction. The rapid reaction gives CrCl " as a product, characterized spectrally after separation by ion exchange from the remainder of the species in solution. It is clear that since CrCl " could not possibly be produced from Cr " and Cl ions during the brief time for reaction and ion-exchanger manipulation, it must arise from the redox pro-... 

The ratio of the distribution coefficients of pertechnetate and perrhenate is about 1.6 to 2, comparable to adjacent rare earth metals. Technetium and rhenium may be separated by ion-exchange chromatography. However, efficient separations require some care and tend to be slow. On the other hand, cation exchange resins adsorb technetiiun only to a negligible extent so that pertechnetate can be rapidly separated from cationic elements . 

Lignin peroxidase activity, (i.e., peroxide-dependent oxidation of veratryl alcohol at pH 3) was not detected over the 30 days tested, while laccase appeared at day 7. Culture medium from day 7 onwards could also oxidize veratryl alcohol to aldehyde with concomitant conversion of oxygen to hydrogen peroxide. This activity, which was optimal at pH 5.0, was named veratryl alcohol oxidase (VAO). The extracellular oxidative enzyme activities (laccase and veratryl alcohol oxidase) could be separated by ion-exchange chromatography (Figure 2). Further chromatography of the coincident laccase and veratryl alcohol oxidase (peak 2), as described elsewhere (25) resulted in the separation of two veratryl alcohol oxidases from the laccase. 

---