Search results for "EXCHANGE"
showing 10 items of 2035 documents
Cu-B alloy - analysis of use possibility as fuel cell cathode catalyst
2016
In recent years there has been a development of non-conventional and renewable sources of energy. One such sources of energy are fuel cells. Fuel cells are ecological and high efficiency sources of electric energy. However, the use of fuel cells on a large scale is limited, mainly by the high cost of catalysts. Platinum is most commonly used as the catalyst. But due to the high price of platinum there’s a need for finding other catalysts. Replacement of platinum will contribute to the fast development of green energy sources. This paper presents a study of possibility of using Cu-B alloy as catalyst for oxygen electrode in fuel cells. Researches were done in glass vessel, on a copper electr…
Tri- and tetranuclear heteropivalate complexes with core {Fe2Ni O} (x = 1, 2): Synthesis, structure, magnetic and thermal properties
2019
Abstract The reactions of complex [Fe2Ni(O)(Piv)6(Et2O)(H2O)2] (1) with 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) gave the following new coordination compounds: the trinuclear complex [Fe2Ni(O)(Piv)6(phen)H2O]·(C2H5)2O (2), the tetranuclear ones [Fe2Ni2(OH)2(Piv)8(phen)2] (3) and [Fe2Ni2(OH)2(Piv)8(bpy)2] (4), depending on the crystallization conditions. According to single crystal X-ray diffraction data, all the compounds have molecular structures. The Mossbauer spectra of 1–3 correspond to high-spin Fe3+ ions in an octahedral environment consisting of oxygen atoms. The DC magnetic susceptibility studies and quantum-chemical analysis of intra- and intermolecular J pathways using…
Synthesis and characterization of new coordination compounds by the use of 2-pyridinemethanol and di- or tricarboxylic acids
2021
The development of synthetic approaches towards new coordination polymers has attracted significant interest due to their fascinating physical properties, as well as their use in a wide range of technological, environmental and biomedical applications. Herein, the initial combination of 2-pyridinemethanol (Hhmp) with 1,4-benzenedicarboxylic acid (H2bdc) or 1,3,5-benzenetricarboxylic acid (H3btc) has been proven a fruitful source of such new species providing access to five new coordination compounds, namely [M2(Hbtc)2(Hhmp)4]·DMF (M = CoII, 1·DMF;NiII, 2·DMF), [Ni(bdc)(Hhmp)2]n·4H2O (3·4H2O), [Zn2(bdc)(hmp)2]n·DMF (4·DMF) and [Fe3(bdc)3(Hhmp)2]n (5). 4·DMF and 5 are the first metal–organic …
Synthesis, crystal structure and magnetic properties of bis[μ-bis(3-(pyridin-2-yl)-1,2,4-triazole-N′,N1,N2)] bis[triaqua nickel(II)] tetranitrate
1998
Abstract A new dinuclear nickel(II) coordination compound of formula Ni2(Hpt)2(H2O)6(NO3)4 (Hpt=3-(pyridin-2-yl)-1,2,4-triazole) was synthesized. The structure was solved at 298 K by single-crystal X-ray analysis. Bisμ-bis(3-(pyridin-2-yl)-1,2,4-triazole-N′,N1,N2) bistriaqua nickel(II) tetranitrate (C14H24N12O18Ni2) crystallizes in the triclinic space group P-1, a=7.2266(1), b=9.9144(1), c=11.2647(1) A, α=66.854(1)°, β=74.000(1)°, γ=86.400(2)°, V=712.42(1) A3, Z=1 (dinuclear units), 2823 reflections (1 > 2σ(I)), R1=0.0442, wR2=0.1197. The Ni(II) ions are bridged by two neutral Hpt ligands coordinating via N1 and N2 in the equatorial plane, Ni(1)-Ni(1)′=4.098(1) A. The Hpt bridging mode is a…
Behavior of Actinium, Alkaline, and Rare Earth Elements in Sr-Resin/Mineral Acid Systems
2015
In this work, the interactions between the divalent alkaline earth elements (AEE) (Sr, Ba, Ra), the trivalent rare earth elements (REE) (Ce-Lu, Y), and Ac(III) with Sr-resin were investigated in the presence of HNO3, HCl, HBr, HClO4, and HPF6. Distribution coefficients of these ions on the Sr-resin were determined under batch-loading conditions. Lastly, online column separations were performed to demonstrate the utility of these systems. Substantial differences in the behavior of the ions in solutions comprised of the five different acids were observed. These differences can partly be explained by a combination of ion exchange (primary) and extraction (solvation) mechanisms. From a practica…
Application of a weakly basic dimethylamino-modified silica ion exchanger to the separation of oligonucleotides
1979
Abstract LiChrosorb RP-8, RP-18 and Diol as well as a newly synthesized basic dimethylamino-modified silica ion-exchanger (DMA-silica) were applied for the separation of adenylic acid, cytidylic acid and uridylic acid oligoribonucleotides. On LiChrosorb RP-8 and RP-18, respectively, in aqueous buffered eluents (K 2 HPO 4 - H 3 PO 4 ), the retention of oligonucleotides was increased with decreasing number of nucleotide units in the solute, i.e., with increasing hydrophobic character. The elution behaviour of ologonucleotides on LiChrosorb Diol followed the same order but took place according to a size-exclusion mechanism. The retention of oligonucleotides on DMA-silica is assumed to be based…
Hydrophobic and cation exchange mechanisms in the retention of basic compounds in a polymeric column.
2004
A cation exchange retention mechanism concomitant with the well-known hydrophobic partition mechanism in a polymeric column has been observed and investigated. This exchange process is attributed to ionization of some acidic sites present in the polymer column at basic mobile phase pH values. Several drugs of different basicity have been chromatographed on a polymeric PLRP-S column with methanol-water and acetonitrile-water mobile phases. The cation exchange between the protonated basic drug and the buffer cations (Na+, K+ and BuNH4+) is observed at the pH range where the protonated drug and the ionized sites of the column coexist. This process produces a shift of the retention versus pH pl…
The determination of the DNA base composition in 19 species of adriatic sponges with high-pressure liquid cation-exchange chromatography.
1976
Abstract The (adenine + thymine)/(guanine + cytosine) base ratios of 19 species of adriatic sponges have been determined by high-pressure liquid cation-exchange chromatography. The base ratios vary from 1.49 (Mycale massa) to 0.63 (Hippospongia communis) according to an (A+T) content of 59.7 and 38.6 mol%, respectively. The DNAs of sponges of the order Keratosa showed marked differences in their (A +T) contents (39.5 to 58.8 mol%) whereas those of Tetractinellida and Halichondrina were nearly identical (39.3 to 40.8 and 49.5 to 49.8 mol%, respectively). The 5-methylcytosine (5MC) content was determined in 8 sponge DNAs by a semiquantitative method. The values differed from 0.8 to 2.2 mol% o…
The second component of human complement: Detection of two hemolytic forms in plasma by pH Variation
1988
The second component of human complement (C2) in pseudoglobulin prepared from normal plasma eluted as a single peak at high conductivity (30 mS) and pH 4.5 from the cationic exchangers S-Sepharose or Mono S in the Fast Protein Liquid Chromatography (FPLC) System. The C2 was stable at pH 4.5 and 0 degrees C if enzyme inhibitors were used and the pH was raised to 6.0 after elution from the columns. After rechromatography on Mono S in the FPLC System at the median isoelectric point of 5.5 or pH 6.0, the C2 eluted as two distinct hemolytic forms: the first peaked at 16 mS, the second at 30 mS. The two forms of C2 did not correlate with the allotypic variant of C2 in individual, normal human pla…
Characterization of aquatic humic substances and their metal complexes by immobilized metal-chelate affinity chromatography on iron(III)-loaded ion e…
2001
The analytical fractionation of aquatic humic substances (HS) by means of immobilized metal-chelate affinity chromatography (IMAC) on metal-loaded chelating ion exchangers is described. The cellulose HYPHAN, loaded with different trivalent ions, and the chelate exchanger Chelex 100, loaded to 90% of its capacity with Fe(III), were used. The cellulose HYPHAN, loaded with 2% Fe(III), resulted in HS distribution coefficients Kd of up to 10(3.7) mL/g at pH 4.0 continuously decreasing down to 10(1.5) at pH 12, which were appropriate for HS fractionation by a pH-depending chromatographic procedure. Similar distribution coefficients Kd were obtained for HS sorption onto Fe(III)-loaded Chelex 100. …