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Attachment of 2,2-bipyridine onto a silica gel for application as a sequestering agent for copper, cadmium and lead ions from an aqueous medium

Souza E. J., Cristante V. M., Padilha P. M., Jorge S. M. A., Martines M. A. U., Silva R. I. V., Carmo D. R., Castro G. R.

Polish Journal of Chemical Technology

2011

Vol. 13, nr 4

28-33

A method was developed to attach 2,2-bipyridine (BP) onto a silica gel surface by a two-step reaction. The fi rst step consisted of a reaction between the matrix and a silylating agent, 3-chloropropyltrimethoxysilane. In the second step of the reaction, a ligand molecule was attached onto Si-CPTS, yielding the product Si-BP. The modified material contained 0.431±0.01 mmol of 2,2-bipyridine per gram of modified silica, as confirmed by FT-IR spectra of the proposed structure. The surface modification was characterized by the BET technique, which revealed a decrease in the surface area from 614 to 450 m2 g-1. The series of adsorption isotherms for the metal ions were adjusted to fit a modified Langmuir equation. The maximum number of moles of copper, cadmium and lead ions adsorbed was 0.64, 0.53, and 0.54 mmol g-1, respectively. The surface saturation was calculated as ¢ fraction and the values obtained, Cu(II) =1.160, Cd(II) = 1.044 and Pb(II) = 0.997, suggest a type 1:1 metal-ligand complex.

Kinetic spectrophotometric determination of ascorbic acid in pharmaceutical formulations

Fathi M. R., Elahi R., Hashemi P.

Chemia Analityczna

2005

Vol. 50, No. 6

1069-1076

Sensitive, simple and fast kinetic spectrophotometrii; method for determination of ascorbic acid has been described. The procedure is based on reduction of iron(IIi) to iron(II) by ascorbic acid and formation of a complex between iron(II) and 2.2'-bipyridine. Reaction rate was monitored spectrophotometrically by measuring the increase in absorbance of the formed complex al 522 nm. Ascorbic acid was determined using a fixed-time (3 min} method in two concentration ranges: 0.1-15 mg mL-1 and 20-45 mg ml.-1: the corresponding correlation coefficients were 0.998 and 0.999, respectively. Relative standard deviation for 10 replicate determinations of ascorbic acid in 2 mg mL-1 solution was 0.47% and detection limit equalled 0.032 μg mL-1. The proposed method was successfully applied to the determination of ascorbic acid in pharmaceutical formulations. Reliability of determination was confirmed applying standard iodimetric method.

Opisano czułą, prosta i szybką metodę oznaczania kwasu askorbowego. Procedura polega na redukcji żelaza(ITI) do żelaza(II) za pomocą kwasu askorbowego i tworzeniu kompleksu żelaza(II) z 2.2'-dipirydyną. Szybkość reakcji mierzono na podstawie wzrostu absorbancji przy 522 nm. Kwas askorbowy oznaczano metodą stałego czasu (3 min) w zakresie stężeń 0,1-15 mgL-1 i 20-45 mgmL-1.Względne odchylenie standardowe, obliczone na postawie 10 pomiarów kwasu askorbowego o stężeniu 2 mg mL-1, wynosiło 047%. a granica wykrywalności - 0,032 μg mL-1. Wiarygodność oznaczeń potwierdzono metodą jodometryczną.

A Novel Tetranuclear Iron Complex [Fe4O2(O2CC2H5)7(bipy)2]PF6.2H2O (bipy=2,2'-Bipyridine):Synthesis, Crystal Structure and Magnetic Properties

Yan B., Chen Z. D.

Polish Journal of Chemistry

2001

Vol. 75, nr 6

785-793

A novel tetranuclear iron-oxo complex has been synthesized and characterized by X-ray single crystal structural analysis: [Fe4O2(O2CC2H5)7(bipy)2]PF6_2H2O (bipy = 2,2_- bipyridine). The title complex crystallizes in the monoclinic system, space group C2/c, with lattice parameters a = 27.859(2) A, b = 13.0629(10) A, c = 17.2698(14) A, _ = 123.6080(10)_, V = 5234.3 (7) A3, Dc = 1.559 Mg/m3, Z = 4, R1 = 0.0493. The molecular structure shows that there are two types of coordination environment for Fe(III) atoms. One is formed by two N atoms and four O atoms, another by six O atoms, all in distorted octahedron, which forms a "butterfly" core structure. The corresponding variable temperature susceptibility measurement shows the antiferromagnetic interactions in the complex.