AG MP-1 Research Articles

An improved 191Os/ 191mIr generator using a hybrid anion exchanger

Iridium-191m is an attractive radionuclide for first-pass radionuclide angiography, but development of an 191Os/ 191mIr generator with high 191mIr yield has proven difficult. The use of trans-dioxobisoxalatoosmate(VI) as a parent species results in a higher initial yield (20 to 25%/mL), but the yield decreases over time. Using an anion-exchange column of tridodecylmethylammonium chloride-treated silica gel and AG MP-1 resin, we have developed an improved 191Os/ 191mIr generator with higher initial yield (25 to 30%/mL) and a slower rate of decrease than the previous design.

Simultaneous Extraction and Methylation of Acidic Analytes Adsorbed onto Ion Exchange Resins Using Supercritical Carbon Dioxide Containing Methyl Iodide

Methylation of a wide range of organic acids with methyl iodide was simply and efficiently performed on anion exchange resins with either supercritical carbon dioxide or acetonitrile as solvents. Analytes including chlorophenoxyacetic acids, pentachlorophenol, and quinoxaline-2-carboxylic acid were displaced from the resin in a single step as they methyl esters or ethers in high yield using the supercritical fluid extraction (SFE) system. The conversion of 2,4-D and 2,4,5-T (solutions of 100 and 35 ppb, respectively) to their methyl esters was complete in 30 min and gave yields of 92% and 99% with coefficients of variation of 10%. Analytes in up to 200 mL of aqueous solution could be trapped on 0.1 g of AG MP-1 anion exchange resin and derivatized and eluted using methyl iodide in supercritical carbon dioxide at 200 bar and 80 o C. Less acidic compounds including albendazole, fenbendazole, triclabendazole, and sulfadimidine could also be derivated on the resin under SFE conditions or in a quick and inexpensive procedure using acetonitrile; however, these compounds gave lower yields and multiple methylated product

Separation of uranium from uraniferous coaly clays using a selective ion-exchange two-step elution system

An ion-exchange process for the selective separation and enrichment of uranium from the main elements Si, Al, Fe, Ca, Mg, Na, K as well as from Mo and V, which are present in uraniferous coaly clays, has been developed. After a selective carbonate leaching of the roasted ore, a 0.5 mol/l Na2CO3/0.5 mol/l NaHCO3 solution was passed through the macroporous ion-exchanger AG MP-1, which at pH10 absorbed uranium quantitatively in form of a carbonato complex. Remaining absorbed amounts of Mo and V were eluted with 0.1 mol/l EDTA in 0.5 mol/l Na2CO3/0.5 mol/l NaHCO3, while U was quantitatively separated by a second elution step with 0.5 mol/l HNO3 and was afterwards precipitated with NH4OH as a high-grade yellow cake. Differential pulse polarography (DPP), atomic absorption spectroscopy (AAS), X-ray fluorescence (XRF), instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS) had been used to determine the uranium content in the raw materials and to investigate the effectivity of the different steps of the developed process.

Evaluation of osmium(II)-nitrosyl complexes as a method to increase the yield of the 191Os- 191mIr generator

The nitrosyl complexes pentachloronitrosylosmate(II), [OsCl 5(NO)] 2−, and hydroxytetranitronitrosylosmate(II), [Os(OH)(NO 2) 4(NO)] 2−, were evaluated as parent species for use on the 191Os- 191mIr generator in an attempt to increase the 191mIr yield of the generator by providing a direct route to a chemically stable 191mIr daughter. The uptake of the 191Os-labeled complexes by the inorganic ion-exchangers ZrO 2, SnO 2, PbS, MnO 2 and Al 2O 3 and the organic resin AG MP-1 was measured and prototype generators were prepared using those exchangers that demonstrated greater than 90% uptake of the 191Os-labeled complexes. The 191mIr(III)-nitrosyl complexes produced subsequent to β − decay of the 191Os-nitrosyl parent complexes were found to undergo secondary chemical reactions to form nitro (NO − 2) complexes that were tightly retained on the ion exchanger limiting 191mIr yield to less than 5%.

Geotrichum candidum NRRL Y‐553 lipase: Purification, characterization and fatty acid specificity

Lipases from Geotrichum candidum NRRL Y-553 are of interest because of their unique specificity for cis-9-unsaturated fatty acids relative to both stearic and palmitic acids. The lipases were partially purified by chromatography on Octyl Sepharose, AG MP-1 macroporous anion exchanger, and chromatofocusing resin. The preparation was found to contain multiple, glycosylated lipases varying slightly in pI (pI 4.88, 4.78, 4.65, 4.57 and 4.52) as judged by both activity and silver staining. The molecular mass determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis was 64 kilodaltons for the main species, with minor species of 60 and 57 kilodaltons present as well. The specificity of the crude lipases for hydrolysis of 4-methylumbelliferyl esters of oleic vs. palmitic acid was 20-to-1. The specificity of the purified, partially separated lipases was similar to that of the crude preparation. Thus the lipases could be used even in crude form for the hydrolysis and restructuring of triacylglycerols on a large scale.

A Comparative Study of Gel-Type and Macroreticular Cation Exchange Resins for the Separation of Rare Earth Elements

Abstract Owing to the macro- and micro- pores in the matrix, macroreticular resins have larger micro-void volume ratio in the ion exchange column chromatography. It is advantageous in the ion exchange kinetics resulting from the quicker mass transfer. By means of EDTA displacement column chromatography for the Pr-Nd separation study, we have found that macroreticular cation exchange resins have higher separation efficiency in HETP, single stage time, and the pure Pr production rate, e. g. for AG 50W-X8, 200∼400 mesh resin (gel-type) and AG MP-50, 200∼400 mesh resin (macroreticular), the HETP values are 0.40 cm and 0.24 cm; the single stage times are 3.11 min and 1.30 min; the pure Pr production rates are 0.19 and 0.68 m mole/hr, respectively. Because both types of resins contain the same functional group, the single stage separation factors for Pr-Nd separation have the same value of 2.0±0.1 at 92°C. The cation exchange resins which were prepared in our laboratory with higher micro-void volume ratio could...

Automated two-column ion exchange system for determination of the speciation of trace metals in natural waters.

A rapid method for determination of metal speciation based on an automated two-column ion exchange system is described. Two fractions of dissolved trace metal species are directly determined by on-line flame atomic absorption spectrophotometry after preconcentration by sequential columns of Chelex-100 chelating resin and AG MP-1 macroporous anion resin. A third fraction is determined by standard addition. Variables that affect the results obtained by the two-column system are studied by the use of model complexing agents. With a 10-mL sample loop, the sample throughput is 6 samples per hour and detection limits are 0.1 micrograms/L for Cu(II), 0.08 micrograms/L for Cd(II), and 0.2 micrograms/L for Zn(II). The method is used to determine the speciation of Cu(II), Cd(II), and Zn(II) in natural water samples.

Measurement and compensation for metal complex dissociation in speciation studies with an automated two-column ion-exchange system

Sample solutions containing trace metal complexes are passed sequentially through columns of Chelex-100 resin and AG MP-1 anion-exchange resin at different flow-rates. For most cases studied, the amounts of metal species retained by each column depend on the flow-rate because the degree of dissociation of the complexes increases with the contact time of the sample solution in the Chelex-100 column. The flow-rate data are used to generate extrapolated values for zero contact time in the columns. The extrapolated values provide a better estimate of the metal speciation in the original sample. The apparent first-order dissociation rate constants of metal complexes are also estimated. For Cu(II)-humate complexes at pH 7, the apparent first-order dissociation rate constant is 0.3–0.6 s −1. The performance of the measurement scheme is also evaluated with sample solutions containing complexes of Cu(II) and Cd(II) with EDTA, NTA, IDA and natural ligands.

Two-column ion-exchange method for the determination of copper-complexing capacity and conditional stability constants of copper complexes for ligands in natural waters

Sample solutions titrated with Cu 2+ ions are passed sequentially through two ion-exchange columns in an automated flow system. The first column is packed with Chelex-100 resin and retains Cu 2+ ions that are free or derived from copper complexes that dissociate in the column. The second column is packed with AG MP-1 anion-exchange resin and retains negatively charged Cu(II) complexes. The retained copper species are then eluted from the columns and determined on-line with a flame atomic-absorption spectrophotometer. It is necessary to correct for a small fraction of free Cu 2+ ions that pass through the first column and are retained by the second column. The Cu(II)-complexing capacity of sample solutions is determined from plots of the concentration ratio of free Cu 2+ ions to Cu(II) complexes vs. the concentration of free Cu 2+ ions. Conditional stability constants of the copper complexes are also estimated from these plots. The complexing capacity of sample solutions is also determined rapidly by measuring the concentration of complexed Cu(II) after spiking the sample with an excess of Cu 2+ ions. The sample solutions tested were 4.0μ M NTA, 4.0-mg/l. humic acid, and a river water.

Distribution coefficients and ion-exchange selectivities for 46 elements with a macroporous cation-exchange resin in hydrochloric acid-acetone medium

Distribution coefficients with the macroporous cation-exchange resin AG MP-50 in HCl-acetone mixtures ranging from 0.2 to 4.0 M HCl and from 0 to 95% acetone have been determined for 46 elements. The ion-exchange behaviour of the elements is discussed, some possible separations are indicated, and elution curves demonstrating separations of the combinations Au(III)BiZnPbSr; Rh(III)InGaCuNi and CdFe(III)LiAlYb are presented.

Separation of traces of manganese, cobalt, nickel and copper from gram amounts of tellurium by cation-exchange chromatography in hydrochloric acid/acetone media

Traces of Mn(II), Co(II), and Ni(II) and minor amounts (up to 20 mg of these elements are separated from gram amounts of tellurium by cation-exchange chromatography on small columns (3 g) of macroporous AG MP-50 resin or larger colunns (5 g) of microporous AG 50W-X8 resin. The trace elements are retained from 0.5 M HCl containing 70% acetone while tellurium passes through and is eluted completely with this solution. The trace elements are then eluted with 3.0 M HCl and can be determined by atomic absorption spectrometry. Copper (II) can also be separated but requires a 10-g column of AG MP-50 resin. Separations are sharp and quantitative and only microgram amounts of tellurium remain in the trace element fraction when a 3-g sample of tellurium dioxide is taken; 10-μg amounts of the trace elements were separated from such samples and determined with standard deviations of <1%. Relevant elution curves and results for the analysis of synthetic mixtures are presented.

Preparative chromatography of oligogalacturonic acids

A mixture of oligogalacturonic acids was prepared by partial enzymatic hydrolysis of citrus pectin-derived α- d-polygalacturonic acid. Both a commercial fungal “pectinase” preparation and a purified endo-polygalacturonase isolated from this source by chromatography on carboxymethyl Sephadex C-50 were used to catalyze the hydrolysis. Different product distributions resulted, but even when using pectinase there was no evidence for the formation of unsaturated products from activity of polygalacturonic acid lyase. Individual oligogalacturonic acids were isolated by step-gradient elution (sodium formate, pH 4.7) from the macroporous strong base anion-exchange resin AG MP-1 in the formate form. Pure oligomers to heptagalacturonic acid were isolated in a single run, including gram quantities of tri-, tetra-, and pentagalacturonic acid. The individual oligogalacturonic acids were characterized by fast-atom bombardment mass spectrometry in positive and negative modes.

Paramolybdate anion-exchange resin, an improved catalyst for the C-1–C-2 rearrangement and 2-epimerization of aldoses

Aqueous solutions of molybdate at 90° bring about the inversion of the C-1–C-2 fragment of aldoses having four or more carbon atoms, generating thermodynamically equilibrated mixtures of the starting aldose and its 2-epimer. In some cases, notably with the aldopentoses, substantial proportions of the 3-epimers are produced, as well as 2-epimers that have not undergone inversion of the C-1–C-2 fragment. These side-reactions can be controlled by using the paramolybdate form of an anion-exchange resin (AG MP-1) together with the formate form of the same resin. The latter acts to scavenge unbound molybdate and paramolybdate anions that appear to be responsible for the side reactions.

THE INFLUENCE OF CROSSLINKAGE ON THE DISTRIBUTION COEFFICIENTS AND ANION EXCHANGE BEHAVIOUR OF SOME ELEMENTS IN HYDROCHLORIC ACID

Equilibrium distribution coefficients are presented for Cu(II), Zn(II), Cd(II), Fe(III), Ga(III), In(III), Th(IV) and U(VI) on the strongly basic anion exchangers AG1-X2, AG1-X4, AG1-X8, AG1-X10 and AG MP-1 in hydrochloric acid. Coefficients generally increase with increase in crosslinkage, while exchange kinetics show a marked improvement with decrease in crosslinkage. Elution curves for some elements on the lower crosslinked resins AG1-X2 and AG1-X4 and on the macroporous resin AG MP-1 demonstrate the advantages of these resins for some separations.

Separation of traces and large amounts of lead from gram amounts of bismuth, tin, cadmium, and indium by cation exchange chromatography in hydrochloric acid-methanol using a macroporous resin

Traces and small amounts of lead can be separated from gram amounts of Bi, Sn, Cd, and In by eluting these elements with 0.5 M HCl in 50% methanol from a column containing only 2.7 mL (1g) of Bio-Rad AG MP-50 macroporous cation exchange resin of 100-200 mesh particle size in the H form. A 5.4 mL (2 g) resin column separates up to 100 mg of lead. Lead can be eluted effectively with 3.0 M aqueous HCl. Separations are sharp and quantitative. In combination with flame atomic absorption spectrometry, the method has been applied for the determination of lead in pure metals or chemicals of the above elements. Relative standard deviations were better than 1% for samples containing 10 ppm of lead or more. The sensitivity is less than 0.1 ppm. Relevant elution curves and results of analyses of binary synthetic mixtures and actual samples are presented. 7 references, 4 figures, 2 tables.

Separation of silver from zinc, cadmium, copper, nickel and other elements in nitric acid with a macroporous resin

Traces of silver and amounts up to 50 mg can be separated from up to gram amounts of Zn, Cu(II), Ni, Co(II), Mg, Be, Ti(IV), V(IV), Li and Na by eluting these with 2.0 M nitric acid from a column containing 54 ml (20 g) of macroporous AG MP-50 cation-exchange resin of 100–200 mesh particle size, in the H +-form. Silver is retained and can be eluted with 0.5 M hydrobromic acid in 9:1 v v acetone-water. Separations are sharp and quantitative and only a few μg of the other elements are found in the silver fraction. Cadmium and manganese (II) can also be separated quantitatively but show tailing and require larger elution volumes. Some typical elution curves and results of analyses of synthetic mixtures are presented.

Anion-exchange chromatography of proteins on AG MP-1 using high-performance liquid chromatography equipment

That the macroporous anion-exchange resin AG MP-1 can be used with HPLC equipment and common aqueous buffers for the chromatography of proteins is shown. The utility of this system is illustrated by the partial purification and complete resolution of the three protein synthesis elongation factors from each other, starting with a crude extract of Escherichia coli. The factors were purified 10- to 30-fold in a yield of 50 to 90% with a single 60-min chromatographic program of increasing NaCl concentration. Other proteins from various biological sources were purified with similar results. Thus, it appears that AG MP-1 is useful, at least in some applications, for the rapid, reproducible, and economical purification of proteins using HPLC equipment.

Distribution coefficients and ion exchange behavior of 46 elements with a macroreticular cation exchange resin in hydrochloric acid

A systematic study of distribution coefficients in aqueous HCl using the macroreticular resin AG MP-50 was undertaken, and the results are here presented and discussed. Because cation exchange distribution coefficients are influenced quite strongly by the degree of cross linkage of the resin and this influence varies considerably depending on the size of the hydration shell of the cation in question, the rigid macroreticular resin with its very high effective cross linkage (about 25%) in the exchange region should show some marked differences in the distribution coefficients of some elements as compared with a 8% cross-linked gel-type resin. It has been shown that the distribution coefficient of magnesium when plotted against percentage of cross linkage shows a maximum at about 12% cross linkage and then slightly decreases again, while that for calcium shows an increase up to 25% cross linkage. As a result, the separation factor between Mg and Ca in 1M aqueous HCl increases from a value of about 2 with an 8% cross-linked gel-type resin to about 8 for the AG MP-50 macroreticular resin. It seems reasonable to assume that some other spectacular increases in separation factors are also possible.

Distribution coefficients and cation-exchange behaviour of 45 elements with a macroporous resin in hydrochloric acid/methanol mixtures

Cation-exchange distribution coefficients are presented for 45 elements with the macroreticular (macroporous) cation-exchange resin AG MP-50 in mixed hydrochloric acid/methanol media, with acid concentrations ranging from 0.5 to 6.0 M, and methanol concentrations from 0 to 90%. The ion-exchange behaviour of the elements is discussed, some possible separations are indicated, and 3 multi-element elution curves are presented, demonstrating the separations of the combinations In-Zn-Ga-Al-Yb; Cd-Li-Cu(II)-Mg-Ca; and Pt(IV)-Te(IV)-V(IV)-Fe(III)-Mn(II).

Purification of reduced nicotinamide adenine dinucleotide by ion-exchange and high-performance liquid chromatography

Combining ion-exchange (AG MP-1) and reversed-phase (C-18) partition chromatography accomplishes a higher degree of purification of NADH than either method can provide alone. Final elution in 95% ethanol, dehydration with anhydrous sodium sulfate, and storage in dry 1,2-propanediol over molecular sieves prevents hydrolysis of the purified dinucleotide.