Koji Ishida

Thin-layer chromatographic behaviour and separation of rare earths in silica gel-aqueous alkali metal chloride systems

SummaryThe thin-layer Chromatographic behaviour of all rare earths except Pm on silica gel in aqueous alkali metal nitrate solutions has been investigated. In all the solutions the tetrad effect is clearly observed in the variations of both the Rf-values and the logarithms of the separation factors relative to Gd with the atomic numbers of the lanthanoids. A brief discussion concerning the effect of the solvent cations and typical chromatograms for the separations of multicomponent mixtures containing adjacent lanthanoids are presented.

Consecutive thin-layer chromatographic separation of Zr(IV), Hf(IV) and many other ions on silica gel in nitric acid-hydrogen peroxide media.

The thin-layer chromatographic (TLC) behaviour of 64 ions including Zr(IV) and Hf(IV) has been surveyed on systems composed of silica gel and of nitric acid and nitric acid-hydrogen peroxide media. In the 0.5 mol 1(-1) HNO(3)-3% (w/v) H(2)O(2) solution, only Hf(IV) adsorbed very strongly, whereas Zr(IV) and many other ions showed no or weak adsorption. Stepwise development with diluted nitric acid and subsequently with nitric acid-hydrogen peroxide solution allowed the consecutive separation of three-component mixtures consisting of Zr(IV), Hf(IV) and one of many other accompanying elements, such as Mo(VI), Nb(V), Th(IV), Ti(IV), U(VI) and rare earths(III), to be conducted simply and effectively.

Thin-layer chromatographic behaviour and separation of zirconium(IV) and hafnium(IV) on silica gel in mineral acid—hydrogen peroxide media

Abstract The thin-layer chromatographic behaviour of Zr(IV) and Hf(IV) on silica gel in HNO3, HCl and H2SO4 media containing various amounts of H2O2 was investigated as a function of the concentration of each component of the respective solvents. In all the systems, Zr(IV) gave much higher RF values than Hf(IV) because of the stronger complexation of Zr(IV) with H2O2, so that the complete separation of the two metals, present in Zr:Hf weight ratios ranging from 20:1 to 1:40, could be accomplished simply and easily without any sample pretreatment.

CONTRIBUTION OF A LOCAL ELECTRIC DIPOLE MOMENT TO THE HYDROPHILIC NATURE OF RU(PHEN)2(1,5,6,10-TETRAAZAPHENANTHRENE)2+ COMPLEX IN AQUEOUS SOLUTIONS

Abstract The [Ru(phen) 2 (taphen)]Cl 2 ·6H 2 O (taphen=1,5,6,10-tetraazaphenanthrene, phen=1,10-phenanthroline) was prepared, and the origin of the hydrophilic nature of this complex ion was discussed mainly by analysis of the 1 HNMR spectra of the D 2 O solutions. The peak systems for the taphen and phen protons could be analyzed in terms of ABX and AA′MM′SS′X 2 models, respectively, implying geometric similarities with [Ru(phen) 3 ] 2+ . The signal for each proton of the taphen ligand appeared at a lower field (0.34–0.67xa0ppm) than that for the phen proton of the corresponding position. These shifts were explained by the internal electric-field arising from a local electric dipole moment in the taphen ligand. The optimum value of the moment was calculated by the assumption of six point-dipoles on the taphen ligand: the estimated moments and directions of the vectors on the bonds where they were situated were 3.8–4.2xa0D for N5→C4 a and N6→C6 a , 0.3–0.4xa0D for C4→C4 a and C7→C6 a , and 0.1–1.0xa0D for C10 b →C4 a and C10a→C6 a . The dipole moment of the complex ion except for the charge is formally calculated to be 5.5–6.5xa0D. Both protonation and hydrogen-bond formation scarcely occurred on the N5 or N6 nitrogen atom of the taphen ligand, which indicated that the local dipole moment was the primary factor determining the hydrophilic nature of the complex ion.

Effects of amine-pretreatment of silica gel on the TLC behaviour of rare earths

The TLC behaviour of all the rare earths except Pm has been examined on silica gel pretreated with aqueous solutions of four different amines [iminodi-2-ethanol, tris(hydroxymethyl)aminomethane, nitrilotri-2-ethanol, and 1,3-diazole] in a 1 mol/l NH4Cl solution. The Rf value of each metal decreased with increasing pKa value of the amines and also with increasing concentration and pH of the amine solution used for the pretreatment. The technique is simple and reproducible, and makes it possible to arbitrarily regulate the adsorbability of silica gel. Thus, the use of the amine-treated silica gels serves to develop many solvent systems for the separation of the rare earths.

Consecutive thin-layer chromatographic separation of Au(III), Pt(IV), Pd(II) and large amounts of associated base metals

SummaryThe TLC system composed of ECTEOLA-cellulose and 2.5 mol/l HCl−2.5 mol/l NaCl−0.6% (w/v) H2O2 solution allows consecutive separations of Au(III), Pt(IV), Pd(II) and a number of associated base metals such as Cr(III), Mn(II), Fe(III), Co(II) Ni(II), Cu(II), Mg, Ca, Ba, Al, Bi(III), Pb(II), Zn(II) and Ag(I) coexisting in an extremely wide range of amounts and ratios, to be conducted completely in a single run. The effectiveness of the present system is verified by applying it to various synthesized samples containing the three noble metals and one of the base metals, Pt-metal powder and two kinds of Au-alloys.

Anion-exchange separation of rhodium and iridium by ECTEOLA-cellulose column

SummaryThe separation of Rh(III) and Ir(IV) in amounts of 20–5300 and 20–7700 μg, respectively, and in ratios of Rh∶Ir=1∶100 to 100∶1 was achieved without cross-contamination by use of a 3 g ECTEOLA-cellulose column. Rh was first eluted with 40 ml of a 3 mol/l HCl-1% (w/v) NaClO3 solution. Ir(IV) was desorbed with 60 ml of a 6 mol/l HCl-0.1% (w/v) NaClO3 solution. Quantitative recoveries were obtained for each metal. The present method provides much better resolution than the other existing anion-exchange methods and can effectively be applied to the separations and recoveries of Rh and Ir(III or IV) present in a more extensive range of amounts and ratios.