Adsorption-spectroscopic method for multielement analysis: Determination of Cr(VI), V(V), Ni(II), and Cu(II) from one sample using a two-layer adsorbent

The possibility of preconcentrating vanadium, chromium, copper, and nickel by the simultaneous adsorption in a flow-through mode on a two-layer adsorbent and the determination of metal ions by diffuse reflectance spectroscopy was studied. The adsorbent was made of a polyacrylonitrile fiber, one layer of which was filled with an AV-17 anion exchanger (PANV-AV-17), while another layer, with a KU-2 cation exchanger (PANV-KU-2). The procedure was based on the simultaneous preconcentration of vanadium and chromium on the first disk and nickel and copper on the second disk, by pumping the analyzed solution through both disks in a flow-through cell. Then, vanadium was determined on the disk of PANV-AV-17 with 8-hydroxyquinoline-5-sulfonic acid in 0.1 M HCl; next, chromium was determined with 1,5-diphenylcarbazide; the complex of vanadium was decomposed by 0.5 M H₂SO₄ and ascorbic acid. In the PANV-KU-2 disk, nickel was determined with dimethylglyoxime and then copper was analyzed with sodium diethyldithiocarbamate; the complex of nickel was decomposed with 1 M HCl. The selectivity factors were determined. A procedure was developed for the dynamic adsorption-spectroscopic determination of the following elements present simultaneously (μg/mL): V, 0.01–0.05; Cr, 0.002–0.015; Ni, 0.02–0.10; and Cu, 0.02–0.15. The results of analysis of model solutions are presented for different component ratios, RSD < 20%.     

Controlled rotational Raman echo recurrences and modulation of high-intensity ultrashort laser pulses by molecular rotations in the gas phase

We show that sequences of femtosecond laser pulses can control the rotational Raman response of a gas mixture, giving rise to a tunable manifold of echo recurrences in the retarded nonlinear-optical response of the gas. Tailored phase masks for high-intensity ultrashort laser pulses are experimentally demonstrated using molecular rotations in the gas phase driven by optimally time-ordered pulse sequences.     

Unusual dependence of the effectiveness of spectral sensitization of the photoconductivity of polycrystalline ZnO on the dye concentration in a mixed monolayer on a semiconductor surface

A nonmonotonic, oscillatory dependence of the effectiveness of spectral sensitization of the photoconductivity of polycrystalline ZnO on the dye concentration in n-octadecylamine and stearic acid monolayers, transferred to the surface of a semiconductor by the Langmuir-Blodgett method, has been observed experimentally. The observed effect is completely different from the monotonic increase of the photocurrent with a peak at some dye concentration in certain films adsorbed on a semiconductor surface from a solution and in films deposited in vacuum. To explain the results, a simple model describing the balance of monomers and dimers of the dye is examined. The solution of the problem is an oscillatory decaying function of the monomer concentration as the total dye concentration in the monolayer increases. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 3, 174–177 (10 August 1996)     

Determination of thiosulfate ions by the complexation of lead thiosulfate with 4-(2-pyridylazo)-resorcinol on the PANF-AV-17 solid phase

A procedure was developed for determining thiosulfate ions; the procedure involved their adsorption as a complex with lead ions at pH 4 on disks of polyacrylonitrile fiber filled with an AB-17 anion exchanger and determination by the reaction with 4-(2-pyridylazo)-resorcinol at pH 10. The analytical range was (0.2–0.8) × 10^?4; the detection limit was 2 μg/mL. The determination did not interfere with metal cations at the level of the maximum permissible concentrations for potable water, as well as 2–15-fold amounts of sulfites, sulfides, and iodides; 100–200-fold amounts of sulfates, pyrosulfates, and bromides; and 1000-fold amounts of chlorides. The developed procedure was used in the analysis of tap water by the “added-found” method (RSD < 20%).     

Macroheterocycles with an endocyclic azo-group. 1. Tetraazamacrocycles obtained from resorcinol

High-dilution azocoupling of bisdiazotized bis-(2-aminophenyl)oligooxa (orthia)alkanes with resorcinol gives tetraazamacrocycles with two endocyclic azo-groups. It is shown that azocoupling occurs exclusively at the 2- and 4-positions of the resorcinol ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 126–130, January, 1988.     

Potentialities of fibrous ion-exchange materials in the determination of sulfate ions by color reactions of barium with organic reagents on a solid phase

The possibility of the determination of sulfate ions with the use of fibrous materials filled with ion exchangers on the basis of color reactions of barium with the organic reagents Arsenazo III, Orthanilic B, and Orthanilic K on a solid phase was examined. A polyacrylonitrile fiber filled the cation exchanger KU-2; anion exchangers AB-17, A-5, ANKF-211, and EDE-10p; and polyampholyte ANKB-50 (PANV-ANKB-50) was used as the support. The study of the different techniques of the sorption of the reaction components demonstrated the efficiency of the two systems involving PANV-ANKB-50. The determination of sulfates is possible because of the sorption of the excess barium remaining after the reaction with sulfate ions in the solution and its detection on the solid phase with a solution of Arsenazo III or the detection of the excess barium remaining after the interaction with the solution of sulfate ions on the solid phase with a solution of Orthanilic K. The calibration plots are linear in the concentration range of sulfate ions 10^?4–10^?5 M.     

Lanthanum-strontium cuprate: A promising cathodic material for solid oxide fuel cells

Samples of lanthanum-strontium cuprate LaSrCuO_3.61 are synthesized by a solid-phase method at 1473 K, in air. Electron diffraction patterns reveal low-intensity satellites whose position is described in the reciprocal space by the (3 + 2)-dimensional space group I4/mmm(αα0, α-α0)00mg. Using a five-layer cell LaSrCuO_4-δ|YSZ|LaSrCuO_4-δ|YSZ|LaCuO_4-δ prepared by isostatic hot pressing, the ionic component of conductivity of LaSrCuO_4-δ is determined (σ_{1179 K} = 3.8 × 10^?3 S cm^?1), which is commensurate with other mixed conductors based on complex oxides of cobalt and iron.     

75th Birthday of M.R. Vyaselev

Chronicle

75th Birthday of M.R. Vyaselev     

Effect of arsenate and phosphate ions on the adsorption and complexation of uranium(VI) with Arsenazo III on the solid phase of the ion exchanger PAN-EDE-10p fibrous anion exchanger

The effect of arsenate and phosphate ions on the adsorption and color reaction of uranium(VI) with Arsenazo III on the solid phase of a fibrous material filled with the EDE-10p anion exchanger was studied in different adsorption processes. We selected the optimum conditions for the system of U(VI)-AsO ₄ ^3? (H₂PO ₄ ^? )-PANV-EDE-10p-Arsenazo III and used this system for the adsorption-spectrophotometric determination of (0.03–0.3) 10^?3 M arsenate, (0.004–0.06) 10^?3 M phosphate, and 0.01–0.1 μg/mL uranyl ions.