Fluorescence microscopy observation of self-organized microstructure formed by a rare earth compound

The morphologies of monolayers containing Eu(TTA)3Phen (TTA=thenoyltrifluoroace-tone, Phen = 1, 10-phenanthroline) were studied at the air/liquid interface on different subphases by fluorescence microscopy (FM). The composite subphase was the basic premise for the stable existence of the rare earth compound at air/liquid interface. The process that rare earth compound phase changes from liquid expanded state to liquid condensed state corresponded to a plateau in the π-A isotherm. In the pure Eu(TTA)3Phen monolayer, rod domains of Eu(TTA)3Phen formed and packed with no order. In the mixed monolayers with stearic acid (SA), phase transition of SA occurred first and formed domains with an electric gradient field, which induced the rare earth compound to form luminescent ring domains. Influence of intermolecular interaction on the self-organized microstructure was revealed.     

Dynamic ion-exchange chromatography with post-column reaction detection for the determination of the rare earth elements in monazites

Summary Separation and determination of lanthanum, cerium, praseodymium, neodymium and samarium in monazites have been achieved by dynamic ion-exchange chromatography. The ore samples are decomposed by sulfuric acid and the rare earths are separated in a group as oxalates. The rare earth elements are then separated from each other on a column of bonded phase silica by gradient elution with 0.05 to 0.5 M lactic acid (pH 3.5) in the presence of 0.01 M sodium 1-octanesulfonate. Post-column reaction with Arsenazo III is used for detection and quantification of the individual rare earth elements. Results are quoted for lanthanum, cerium, praseodymium, neodymium and samarium in monazites. Detection limit is 1 μg ml⁻¹ with a S/N ratio of 3. The separation is complete within 27 min valley to valley resolution. Precision of better than 1% can usually be obtained.     

The UHPLC-DAD fingerprinting method for analysis of extracellular metabolites of fungi of the genus <Emphasis Type="Italic">Geosmithia</Emphasis> (Acomycota: Hypocreales)

A new simple ultra-high-performance liquid chromatography method with diode array detection (UHPLC-DAD) was developed for chemical fingerprinting analysis of extracellular metabolites in fermentation broth of Geosmithia spp. The SPE method employing Oasis MCX strong cation-exchange mixed-mode polymeric sorbent was chosen for extraction of the metabolites. The analyses were performed on an Acquity UPLC BEH C18 column (100 × 2.1 mm i.d.; particle size, 1.7 μm; Waters) using a gradient elution program with an aqueous solution of trifluoroacetic acid and acetonitrile as the mobile phase. The applicability of the method was proved by analysis of 38 strains produced by different species and isolated from different sources (hosts). The results revealed the correlation of obtained UHPLC-DAD fingerprints with taxonomical identity.     

Neutron activation analysis of rare earth impurities in metallic uranium

A method with a sensitivity of 2·10⁻⁷ to 1·10⁻¹⁰% has been developed for determining Yb, Ho, Dy, Gd, Eu, Sm and La impurities in metallic uranium by means of neutron activation. The method is based on a preliminary chromatographic separation of the total amount of rare earth elements from uranium by passing the solution in sulphuric acid through KU-2 cation exchange resin and eluting the traces of uranium retained by the resin with a solution of ascorbic acid. The rare earth impurities are then eluted from the resin with 4–5N HCl, evaporated, and irradiated for 20 hours with a neutron flux of 1.2·10¹³ n·cm⁻²·sec⁻¹. Subsequently the traces of the rare earth elements are co-precipitated with Fe(OH)₃, dissolved in concentrated HCl and separated from the iron and other impurities by passing the solution through Dowex 1X8 anion exchange resin in the chloride form. The individual rare earth elements are then separated from each other using KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutyrate as the eluant.     

Peculiarities of phase transformations in aqueous isopropanol solutions

Peculiarities of phase transformations in aqueous isopropanol solutions are studied in the range from room temperature to −15°C. It is found that solution cooling results in the formation of macroaggregates with regular geometrical shapes, which are dispersed in the liquid phase and directedly move in the field of a temperature gradient. In aqueous isopropanol solutions with concentrations of 10–30 vol %, the aggregates are formed at temperatures of −10 to −15°C. The average aggregate size is several millimeters. Under the action of a temperature gradient, the aggregates move to the region of higher temperatures. At temperature gradients of 1–2 K/cm, the aggregate velocity is 1–2 mm/s. The characters of the motion and interaction of aggregates are very sensitive to the temperature distribution in a solution. After the aggregate motion ceases, crystallization of the liquid phase that initially is outside of the aggregates is observed.     

Spectrophotometric determination of rare earth metals with 1-(2-pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-naphthol (PAN) reacts very sensitively with rare earth metals to form a deep red precipitate in alkaline solution; this can be extracted with ether, except in the case of lanthanum, cerium and scandium. Absorption maxima occur at 530 and 560 mμ. Traces of rare earth metals may be determined in the presence of many foreign metals.     

Separation and continuous determination of the light rare earth elements and thorium in Baotou Iron Ore by a micro-column

A method for continuous determination of the light rare earth elements (LREEs) and thorium in Baotou Iron Ore was established. The light rare earths and thorium were adsorbed on a micro-column packed with HD-8 cation exchange resins. The light rare earth elements were eluted with 4 mol L⁻¹ HCl–2 mol L⁻¹ NH₄Cl solution and determined with tribromo-arsenzao by a 721-E spectrophotometry at 630 nm; thorium was eluted with 5% potassium oxalate solution and determined with Arsenazo III by a 721-E spectrophotometry at 660 nm. The measured values by the proposed method were in close agreement with the certified values (Baotou main ore standard sample, Baotou ore R-715 standard sample and GSD-2 standard sample). The RSD of the light rare earths and thorium in Baotou Iron Ore were of <1.70% and <1.99%, respectively.     

Multitracer study on permeation of rare earth elements through a supported liquid membrane

Separation by means of supported liquid membranes is a useful method for the preparation and preconcentration of radioactive nuclides. The permeation of rare earth elements through a bis(2-ethylhexyl) hydrogen phosphate-decalin membrane supported on a microporous polytetrafluoroethylene sheet was studied using a multitracer containing radioactive nuclides of Sc, Zr, Nb, Hf, Ce, Pm, Gd, Yb, and Lu. Permeation rates of these elements from feed solutions of various acidity to receiving solutions of 0.5 mol·dm⁻³ HCl were determined simultaneously. The feed solution at pH 1.4 gave the highest permeation rate for Ce, Pm, and Gd, amounting to about 95% of permeation for Ce and Pm, 80% for Gd, and 10% for Yb in 21 h. Scandium, Zr, Nb, Hf, and Lu were not transported at all from the feed solution. Permeation rates of Yb and Lu from the feed solution at pH 1.4 to receiving solutions of 0.75, 1.0, 2.3, and 4.0 mol·dm⁻³ HCl increased with the concentration. The results obtained indicate that the light rare earth elements can be separated from the heavy ones by this method.     

Separation of rare earth,nuclear-fuel burn-up monitors in the 10−9 mole range by high-pressure liquid chromatography with UV-detection

Anion-exchange chromatography of the rare earth (Sm, Nd, Pr, Ce) ions in methanol-nitric acid-water media is performed using high-pressure liquid chromatography. The separation method is especially designed for determination of¹⁴⁸Nd in the nuclear fuel cycle in order to find precise burn-up values. The high-pressure liquid chromatography method presented here is very fast, gives high resolutions, and enables collection of selected fractions containing nmoles of rare earth by UV monitoring at 280 nm of the eluate.     

Use of short columns and high flow rates for rapid gradient reversed-phase chromatography

Summary Rapid analyses were performed using reversed-phase liquid chromatography with short (20–100 mm) columns swept by fast yet shallow gradients, and the results compared with those obtained with 150 mm columns and slow gradients. The resolution losses incurred with shorter columns were minimised by employing elevated flow rates, to ensure that comparable mean retention factors were experienced by individual analytes during gradients run on different columns. This conserves gradient steepness. High quality performance was obtained with turn-around times of 5–10 minutes. An overall 5-fold enhancement in the rate of information generation was obtained. The relevance of instrumental parameters and of column and packing dimensions, upon the potential for improved performance is discussed. Some implications for the rapidly developing technique of capillary electrochromatography are briefly indicated.     

Partition countercurrent chromatography in inorganic analysis

Summary Partition countercurrent chromatography can be used for the concentration and separation of elements of similar properties in aqueous solution — extradant systems. The angle of wetting of the column wall with the components of a two-phase liquid system has a considerable effect on the retention of the stationary phase. The method was used for the separation of orthophosphate and pyrophosphate (extradant — solution of dinonyltin dichloride in methylisobutylketone), cesium and strontium (solution of cobalt dicarbollide in nitrobenzene) and rare earth elements (di-2-ethyhexylphosphoric acid in decane).

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Gegenstrom-Verteilungs-Chromatographie in der anorganischen Analyse

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Surface tension of pure liquid lanthanide and early actinide metals

A systematic theoretical study of the surface tension of liquid rare earth metals and early actinides is performed. An equation, based on the theoretical considerations suggested by Eyring, enables one to calculate the surface tension of elementary substances in a wide temperature range from melting to boiling points. The results of temperature-dependent surface tension calculations of a pure liquid terbium (1629–1880?K) are fitted as γ?=?845?0.1 (T???T _m) (mJ?m²), where the surface tension decreases linearly with temperature. The surface tension was also calculated, at melting points, for all the liquid rare earth metals from La to Lu and for the first six metals of the actinide series from Ac to Pu. It is observed that the lanthanides may be divided into three groups in accordance with their electronic structure. Mostly, the calculated results agree well with available experimental data.     

Simultaneous determination of twelve water- and fat-soluble vitamins by high-performance liquid chromatography with diode array detection

Summary A novel method for the simultaneous determination of twelve water- and fat-soluble vitamins has been established by high-performance liquid chromatography with diode array detection. The vitamins were analyzed on a μBondapak C₁₈ column (300 × 3.9 mm, 10 μm) with methanol-KH₂PO₄ buffer (0.1 M, pH 7.0)-water as mobile phase in a gradient. The linearity of calibration graphs was compound-dependent and the detection limits ranged from 0.02 μg mL⁻¹ to 0.5 μg mL⁻¹. The method was successfully applied to determine vitamins in pharmaceutical preparations. The recoveries were from 95.1% to 103% and the relative standard deviations were in the range of 0.9% to 4.5%.     

Reversed-phase thin-layer chromatography of the rare earth elements

Summary Partition chromatographic behaviour of the rare earth elements on C₁₈ bonded silica reversed-phase material has been investigated by thin-layer chromatography in methanol — lactate media. The rare earth lactato complexes are distributed and fractionated on bonded silica layers without ion-interaction reagents. The concentration and pH of lactate solution, methanol concentration and temperature have effects on the migration and resolution of the rare earth elements. The partition system is particularly suited to separate adjacent rare earths of middle atomic weight groups, allowing the separation of gadolinium, terbium, dysprosium, holmium, erbium and thulium to be achieved by development to 18 cm distance.     

On the utility of predictive chromatography to complement mass spectrometry based intact protein identification

The amino acid sequence determines the individual protein three-dimensional structure and its functioning in an organism. Therefore, “reading” a protein sequence and determining its changes due to mutations or post-translational modifications is one of the objectives of proteomic experiments. The commonly utilized approach is gradient high-performance liquid chromatography (HPLC) in combination with tandem mass spectrometry. While serving as a way to simplify the protein mixture, the liquid chromatography may be an additional analytical tool providing complementary information about the protein structure. Previous attempts to develop “predictive” HPLC for large biomacromolecules were limited by empirically derived equations based purely on the adsorption mechanisms of the retention and applicable to relatively small polypeptide molecules. A mechanism of the large biomacromolecule retention in reversed-phase gradient HPLC was described recently in thermodynamics terms by the analytical model of liquid chromatography at critical conditions (BioLCCC). In this work, we applied the BioLCCC model to predict retention of the intact proteins as well as their large proteolytic peptides separated under different HPLC conditions. The specific aim of these proof-of-principle studies was to demonstrate the feasibility of using “predictive” HPLC as a complementary tool to support the analysis of identified intact proteins in top-down, middle-down, and/or targeted selected reaction monitoring (SRM)-based proteomic experiments.     

Calculation of amino acid hydrophilicity indices for retention of peptides on amide, diol and silica columns in normal-phase liquid chromatography

Summary A set of hydrophilicity parameters in a normal-phase liquid chromatography of peptides is presented in order to clarify the contribution of individual amino acid residues to peptide retention and to predict retention times. The retention of 100 peptides was studied using normal-phase liquid chromatography on amide, diol and silica columns. An acetonitrile-water mixed solution containing 0.2% trifluoroacetic acid +0.2% triethylamine was used as the mobile phase in a linear gradient elution system. The contribution of each residue upon retention was calculated by linear multiple regression analysis. This paper described the contribution values as “hydrophilicity retention coefficients”. Using these hydrophilicity retention coefficients, retention times could be predicted for peptides of known amino acid content and sequence. A set of hydrophilicity retention coefficients on each column was successfully explained by contributions to the degree of retention.     

Simultaneous determination of trace metals by solid phase absorptiometry: application to flow analysis of some rare earths

Solid phase absorptiometry was applied to the simultaneous flow analysis of trace metals in combination with a micro black flow-through cell packed with ion exchanger beads and a multi-channel photodetector connected with optical fibers. A 4.0 cm³ sample solution containing five rare earth metal ions (Dy, Ho, Tm, Er and Nd) was introduced into a flow system and these metal ions were concentrated on a cation exchanger (Muromac 50W-X4) in a flow-through cell. The absorbance increases originating from the f-f or d-f transition bands of these metal ions were directly and continuously measured at 910 nm for Dy, at 530 nm for Ho, at 683 nm for Tm, 522 nm for Er and at 790 nm for Nd, respectively. A multi-variable analysis method was combined with the flow analysis because the absorption spectra of the five rare earth metal ions partly overlapped one another. Although no coloring reagents were used, the proposed method was about ?200 times more sensitive than the corresponding solution method. The reproducibility of this method was less than ± 5%. The detection limits were 0.03, 0.40, 0.30, 0.35 and 0.23 mg dm^–3 for Dy, Ho, Tm, Er and Nd, respectively. Five rare earth metal ions could be precisely determined in practical samples such as yttrium concentrate. Received: 14 March 2000 / Revised: 24 May 2000 / Accepted: 28 May 2000     

功能性离子液体在金属萃取分离中的研究进展

近年来,离子液体在金属萃取领域的研究受到广泛关注,主要集中在两个方面,一是疏水性离子液体作为“绿色”溶剂用于金属离子萃取;二是带有官能团的功能性离子液体作为萃取剂用于金属离子萃取,其中,后者是目前研究的热点。 本文主要对近年来功能性离子液体萃取分离放射性金属、重金属和稀土金属等研究进行综述,并对其未来发展进行了展望。     

Isolation of oxygen-containing monoterpenoids of essential oils by preparative adsorption chromatography with gradient elution

A simple and effective procedure for the comparative chromatography of 1–2 ml of essential oils on a 40×250 mm column of silica gel with gradient elution by hexane-diethyl ether has been developed. A simple system of preparing the mobile phase permits the creation of a continuous gradient during chromatography. The efficacy of the procedure has been shown taking as an example the isolation of fenchone from fennel essential oil. A. V. Dumanskii Institute of Colloid Chemistry and the Chemistry of Water, Ukrainian Academy of Sciences, Kiev. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 634–637, September–October, 1991.