β-Cyclodextrin-grafted magnetic graphene oxide nanocomposites in ultrasound-assisted dispersive magnetic solid-phase extraction for simultaneous preconcentration of lead and cadmium ions

Research on Chemical Intermediates - This article presents an ultrasound-assisted dispersive magnetic solid-phase extraction method (USA-DMSPE) to preconcentration Cd(II) and Pb(II) simultaneously....     

Synthesis and activity measurement of some water-gas shift reaction catalysts

The effect of calcination temperature on the activity and some properties of low temperature water gas shift reaction catalysts has been investigated. The activities of catalysts have been determined using a fixed bed catalytic reactor. The following results may be deduced from the present study. 1. The catalysts' total surface area decreased with increasing calcination temperature, presumably due to the partial sintering of the catalysts particles. 2. The presence of an amorphous CuO phase within the structure of some catalysts may be related to the desirable conditions prevailing during synthesis of the latter. 3. Observation of a similar trend between the increase in copper crystallite particle size and enhancement of catalyst activities with increasing calcination temperature demonstrates the important contribution made by the copper crystallite phase to the overall activities of water gas shift reaction catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.     

Template‐Free Synthesis of Highly b‐Oriented MFI‐Type Zeolite Thin Films by Seeded Secondary Growth

Highly b‐oriented, closely packed, MFI zeolite films are prepared on seeded stainless‐steel plates using organic template‐free, secondary growth solutions, containing aluminum sulfate as a crystallization agent. The number of a‐oriented twin crystals is significantly reduced, and even eliminated, simply by restricting the pH value of the secondary growth solution to the narrow range of 11.1–11.3. Values of pH can be adjusted through the controlled addition of (NH₄)₂SO₄ or H₂SO₄ to secondary growth solutions of the composition (1 SiO₂:0.57 NaOH:137.5 H₂O:0.0050 (Al₂(SO₄)₃?18 H₂O)) or by simply decreasing the molar composition of NaOH with no extra additives.     

Cu (II)‐β‐cyclodextrin complex stabilized on magnetic nanoparticles: A retrievable hybrid promoter for green synthesis of spiropyrans

The magnetic core of manganese ferrite (MnFe₂O₄) nanoparticles has a significant stability in comparison with ferrite (Fe₃O₄) nanoparticles. The unique supramolecular properties of β‐cyclodextrin (β‐CD), such as hydrophobic cavity, hydrophilic exterior and ‐OH functional groups, make it a good candidate for functionalization and catalytic application. So, a surface‐modified magnetic solid support with the Cu (II)‐β‐CD complex was prepared. The structure of nanoparticles was characterized by Fourier transform‐infrared spectroscopy, X‐ray powder diffraction, thermogravimetric analysis, vibrating‐sample magnetometry, inductively coupled plasma‐optical emission spectrometry and scanning electron microscope analyses. The catalytic activity of these nanoparticles was investigated in the synthesis of spiropyrans and high yields of desired products obtained under green media. Some advantages of this novel catalyst for this reaction are high yields, short reaction times, green solvent and conditions, easy workup procedure, negligible copper leaching, reusability without a significant diminish in catalytic efficiency, and simple separation of nanocatalyst by using an external magnet alongside the environmental compatibility and sustainability.     

New Cycloartane and Flavonol Glycosides from Corchorus depressus

Two new monodesmosidic cycloartane triterpene glycosides, depressosides E and F, and two new flavonol glycosides, depressonol A and B, were isolated from the butanol‐soluble part of the EtOH extract of Corchorus depressus L . The structures of the new compounds were elucidated as (22R,24S)‐22,25‐epoxy‐9,19‐cyclolanostane‐3β,16β,24‐triol 3‐[α‐L ‐rhamnopyranosyl‐(1→4)‐β‐D ‐glucopyranoside] ( 1 ), (22R,24S)‐22,25‐epoxy‐9,19‐cyclolanostane‐3β,16β,24‐triol 3‐[α‐D ‐glucopyranosyl‐(1→3)‐β‐D ‐glucopyranoside] ( 2 ), kaempferol 3‐[β‐D ‐glucopyranosyl‐(1→4)‐β‐D ‐galactopyranoside] 7‐[α‐L ‐arabinofuranoside] ( 4 ), and kaempferol 3‐[β‐D ‐glucopyranosyl‐(1→6)‐β‐D ‐galactopyranoside] 7‐[α‐L ‐arabinofuranoside] ( 5 ) on the basis of chemical evidence and detailed spectroscopic studies.     

Cobalt determination with FI-FAAS after on-line sorbent preconcentration using 1-nitroso-2-naphthol

The suitability of 1-nitroso-2-naphthol (NN) as a complexing agent for on-line preconcentration of cobalt using C(18) microcolumn with FI-FAAS system has been tested. Various parameters affecting the complex formation and its elution were optimized. Reagent solution (2.5x10(-3) mol l(-1)) and aqueous sample solution acidified with 0.1% (v/v) nitric acid were on-line mixed in a reaction coil set at 65+/-1 degrees C and flowed through the microcolumn for 30 s. The pH of the mixed solution was adjusted to 3 approximately 4 by adding HNO(3) (1 mol l(-1)) or NaOH (1 mol l(-1)) in the reagent solution. The adsorbed complexes in the microcolumn were eluted with ethanol (acidified to 1% nitric acid) in 10 s into the nebulizer of FAAS. A good precision (1.6% for 100 mug l(-1) Co(II), n=10), high enrichment factor 17.2, with detection limit (3sigma) 3.2 mug l(-1), and sample throughput (90 h(-1)) were obtained. The method was applied on the certified reference materials (CRMs) i.e. NBS-362 and NBS-364 (special low alloy steel), for the determination of cobalt and the results were in good agreement with the certified values.     

Palladium(II) and platinum(II) complexes of Schiff bases derived from 2,6-diacetylpyridine and S-methyldithiocarbazate and the X-ray crystal structure of the [Pd(mdapsme)Cl] complex

Condensation of 2,6-diacetylpyridine (dap) with S-methyldithiocarbazate (smdtc) in a 1:2 molar ratio yields a bicondensed pentadentate Schiff base (H₂dapsme) which reacts with K₂MCl₄ (M = Pd^II, Pt^II) giving stable complexes of empirical formula, [M(dapsme)] · 0.5Me₂CO. These complexes have been characterized by a variety of physico-chemical techniques. Condensation of dap with smdtc in a 1:1 molar ratio also yields the bicondensed Schiff base (H₂dapsme) as the major product, but a mono-condensed one-armed Schiff base (Hmdapsme) is also obtained as a minor product. The latter reacts with K₂PdCl₄ in an EtOH–H₂O mixture yielding a crystalline complex of empirical formula, [Pd(mdapsme)Cl], the crystal structure of which has been determined by X-ray diffraction. The complex has a distorted square-planar structure in which the ligand is coordinated to the palladium(II) ion as a uninegatively charged tridentate chelating agent via the pyridine nitrogen atom, the azomethine nitrogen atom and the thiolate sulfur atom; the oxygen atom of the acetyl group does not participate in coordination.     

Thermotropic polyesters. 1: Synthesis, characterization and thermal transition of poly[4,4-bis(ω-alkoxy)biphenyl isophthalate]

A new homologous series of thermotropic polyesters has been synthesized by polycondensation reaction between isophthaloyl chloride and mesogenic diols 4,4^′-bis(ω-hydroxyalkoxy)biphenyl in which the spacer length is varied from 3 to 6 methylene units. The thermal behavior of the polymers has been characterized using polarized light microscopy and differential scanning calorimetry (DSC). The odd members exhibit a smectic C (S_C) phase in a narrow temperature interval, while the even members form a smectic A (S_A) phase in a broader temperature range. All of the obtained compounds were characterized by conventional spectroscopic methods.     

Synthesis of 2-arylbenzimidazoles catalyzed by transition metal nitrates

A simple and practical procedure for synthesis of 2-arylbenzimidazoles by a one-pot condensation of o-phenylenediamine with aromatic aldehydes in the presence of a catalytic amount of M(NO₃)₂·6H₂O (M = Mn, Fe, Co, Ni, Cu) in ethanol at room temperature is described. Major advantages of this practical procedure are use of a readily available catalyst, high yields, short reaction times, and simplicity of the reaction and workup.     

On-line spectrophotometric determination of scandium after preconcentration on XAD-4 resin impregnated with nalidixic acid

An on-line scandium preconcentration and determination method was developed with spectrophotometer associated with flow injection. Scandium from aqueous sample solution of pH 4.5 was selectively retained in the minicolumn containing XAD-4 resin impregnated with nalidixic acid at a flow rate of 11.8 mL min^?1 as scandium–nalidixic acid complex. The scandium complex was desorbed from the resin by 0.1 mol L^?1 HCl at a flow rate of 3.2 mL min^?1 and mixed with arsenazo-III solution (0.05 % solution in 0.1 mol L^?1 HCl, 3.2 mL min^?1) and taken to the flow through cell of spectrophotometer where its absorbance was measured at 640 nm. The preconcentration factors obtained were 35 and 155; detection limits of 1.4 and 0.32 μg L^?1 and sample throughputs of 40 and 11 were obtained for preconcentration time of 60 and 300 s, respectively. The tolerance limits of many interfering cations like Th(IV), U (VI), rare-earths and anions like tartrate, citrate, oxalate and fluoride were improved. The method was successfully applied to the determination of scandium from mock seawater samples and good recovery was obtained. The method was also validated on certified reference material IAEA-SL-1 (lake sediment) and the result was in good agreement with the reported value.