Facile reduction of aromatic nitro/azido functionality on solid support employing Al/NiCl2·6H2O and Al/NH4Cl: synthesis of pyrrolo[2,1-c][1,4]benzodiazepines

An efficient and mild method for the reduction of aromatic nitro and azido groups on solid support using Al/NiCl₂·6H₂O and Al/NH₄Cl is described. This solid phase reduction technique has been applied towards the synthesis of DNA binding pyrrolo[2,1-c][1,4]benzodiazepine antitumour antibiotics.     

Structure and Magnetic Properties of Nickel–Zinc Ferrite Nanoparticles Prepared by Glass Crystallization Method

Summary. The magnetic and microstructure properties of Fe₂O₃–0.4NiO–0.6ZnO–B₂O₃ glass system, which was subjected to heat treatment in order to induce a magnetic crystalline phase (Ni_0.4Zn_0.6-Fe₂O₄ crystals) within the glass matrix, were investigated. DSC measurement was performed to reveal the crystallization temperature of the prepared glass sample. The obtained samples, produced by heat treatment at 765°C for various times (1, 1.5, 2, and 3 h), were characterized by X-ray diffraction, IR spectra, transmission electron microscopy, and vibrating sample magnetometer. The results indicated the formation of spinel Ni–Zn ferrite in the glass matrix. Particles of the ferrite with sizes ranging from 28 to 120 nm depending on the sintering time were observed. The coercivity values for different heat-treatment samples were found to be in the range from 15.2 to 100 Oe. The combination of zinc content and sintering times leads to samples with saturation magnetization ranging from 12.25 to 17.82 emu/g.     

Photoreaction of 2′-chloro-4-R-benzanilide: synthesis of 2-(4-R-phenyl)-1,3-benzoxazole and 9-R-phenanthridin-6(5H)-one (R=H, CH3, CH3O)

The UV photolysis of 2′-chloro-4-R-benzanilides in acetonitrile solution under nitrogen atmosphere leads to the formation of intramolecular photocyclization products (9-R-phenanthridin-6(5)-one, 20–30%), along with the minor photoreduction, photo-Fries, and intramolecular photosubstitution products. The photoreaction of 2′-chloro-4-R-benzanilide in acetonitrile solution containing 10% of water or aqueous sodium hydroxide however gives 2-(4-R-phenyl)-1,3-benzoxazole as a major product (30%) along with the photoreduction, photo-Fries and intramolecular photocyclization products.     

Use of spectroscopy of gamma-radiation from the inelastic scattering of reactor fast neutrons for elemental analysis

Gamma-spectra of stainless-steel and soil samples have been measured to study the potentialities of using spectroscopy of γ-radiation from the inelastic scattering of reactor fast neutrons for element analysis of various materials. Contents of iron, chromium, nickel, manganese, silicon and titanium in stainless steel, and those of silicon, iron, aluminium, magnesium, calcium, sodium, titanium, carbon and oxygen in soil have been determined by comparing the spectra of the samples with those of specially prepared mixtures of elements. The distinguishing features, advantages, and limitations of this method are discussed.     

14 MeV neutron activation analysis of gold jewellery

Samples of nominal 18 carat and 21 carat gold jewelleries from the local market were non-destructively bulk analyzed using neutron activation analysis. Neutrons of 14 MeV energy were used with a fast pneumatic sample transfer system. The actual gold contents, as well as the composition of the base metals in these samples were determined. The fast neutron activation was found to be an efficient, quick and accurate method of characterizing the precious metal objects routinely in bulk, with a large sample throughput. The results demonstrate the commercial availability of the technique for non-destructive bulk analysis of precious metal objects.     

Membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene–perfluorovinyl ether)

Some properties of the membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene-perfluorovinyl ether) copolymer (PFA) films have been investigated. The dimensional change caused by grafting and swelling behavior, water uptake, electrical conductivity, and mechanical properties of the grafted films were found to increase as the grafting proceeds. The influence of the preparation conditions (such as preirradiation dose, monomer concentration, grafting temperature, and film thickness) on those properties was studied. These properties were found to be dependent mainly on the degree of grafting regardless of grafting conditions, except at higher monomer concentration (>40 wt %). The electric conductivity and mechanical properties for the membranes obtained at higher AAc concentrations were lower than those obtained at lower ones. Analysis by x-ray microscopy of the grafted films revealed that the grafting begins at the part close to the film surface and proceeds into the central part with progressive diffusion of monomer to give finally homogeneous distribution of the electrolytes in the whole bulk of the polymer. The membranes show good electrochemical and mechanical properties which make them acceptable for practical use as cation-exchange membranes.     

Comparative studies on the adsorption and association of 3-methylxanthine and 7-methylxanthine at a charged interface

Summary A systematic comparative study of the adsorption and association of 3-methylxanthine (3MXan) and 7-methylxanthine (7MXan) at mercury-solution interfaces in acidic, neutral, and alkaline buffer solutions was undertaken by ac voltammetry. At bulk concentrations of3MXan above a threshold value, the stacking interactions between vertically oriented molecules lead to a slow reorientation aroundE _ecm, and the molecules adopt a perpendicular orientation. The association of the adsorbed molecules of7MXan is hindered and is not effective in promoting base-base stacking interactions. The enhanced surface activity of3MXan compared to7MXan results from the different position of the methyl group in the purine moiety. The effect of some divalent metal ions on adsorption stages and association of the investigated compounds has been studied. The results indicate that the complexation of methylated xanthine enhances the stacking interactions and hence would be expected to facilitate the formation of perpendicularly stacked layers ofM(II)-MXan complexes on the electrode surface. The adsorption parameters of the investigated compounds have been computed in absence and presence of Cu(II) at differentpH values. The results are compared with the behaviour of xanthine.

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Vergleichende Untersuchungen zur Adsorption und Assoziation von 3-Methylxanthin und 7-Methylxanthin an einer geladenen Grenzfläche

Zusammenfassung Eine systematische vergleichende Untersuchung zur Adsorption und Assoziation von 3-Methylxanthin (3MXan) und 7-Methylxanthin (7MXan) an Quecksilber-Lösungs-Grenzflächen wurde mittels AC-Voltammetrie in sauren, neutralen und basischen Pufferlösungen durchgeführt. Oberhalb einer bestimmten Grenzkonzentration kommt es durch Wechselwirkungen zwischen vertikal angeordneten3MXan-Molekülen zu einer langsamen Reorientierung umE _ecm, was zu einer senkrechten Anordnung führt. Die Assoziation von7MXan ist gehindert und erlaubt daher keine ausgeprägten Basen-Basen-Wechselwirkungen. Die erhöhte Oberflächenaktivität von3MXan gegenüber7MXan resultiert aus der unterschiedlichen Stellung der Methylgruppe am Purinrest. Der Effekt einiger zweiwertiger Metallionen auf die Adsorption und Assoziation von3MXan und7MXan wurde untersucht. Die Ergebnisse weisen auf eine Begünstigung der Wechselwirkungen hin; die Bildung von vertikal angeordneten Grenzschichten an der Elektrodenoberfläche sollte daher im Fall vonM(II)-Mxan-Komplexen erleichtert sein. Die Adsorptionsparameter der untersuchten Verbindungen wurden in Abwesenheit und in Gegenwart von Cu(II) bei verschiedenenpH-Werten berechnet. Die Ergebnisse werden mit dem Verhalten von Xanthin verglichen.

     

Determination of trace alkaline earth metals in brines using chelation ion chromatography with an iminodiacetic acid bonded silica column

The chromatographic behaviour of alkaline earth metals on iminodiacetic acid bonded silica was studied. It was found that the ionic strength of the eluent greatly affected both retention time and selectivity by controlling the extent to which either simple ion exchange or surface complexation was responsible for retention. With a 0.1 M KNO3 eluent, the retention order was Mg(II), Sr(II), Ca(II) and Ba(II), indicating a strong contribution to retention from ion exchange. However, when using a 1.5 M KNO3 eluent, Ba(II) was found to elute first, indicating complexation to be more dominant under these conditions (pH 4.2). The effect of the ionic strength of the sample was also studied and it was found that by matching the eluent cation with that of the sample matrix, efficient separations of alkaline earth metals in 1.0 M NaCl and KCl brines could be obtained without matrix system peaks. Using post-column reaction with o-cresolphthalein complexone, trace levels of Ca(II) and Mg(II) were determined in medicinal NaCl saline solution and laboratory-grade KCl.     

Decomposition of vegetables for determination of Zn,Cd, Pb and Cu by stripping voltammetry

A simple and accurate digestion method using nitric acid, perchloric acid and hydrogen peroxide has been developed for use in trace analysis for heavy metals in vegetables by differential pulse anodic stripping voltammetry. The recovery of the metals from the samples is lower if the hydrogen peroxide is omitted from the digestion mixture. Standard reference materials have been analysed satisfactorily by this method.     

Determination of camptothecin in biological fluids using reversed-phase high-performance liquid chromatography with fluorescence detection

Camptothecin, a plant alkaloid with antitumor activity, is a potent and rapidly acting inhibitor of DNA synthesis. The objective of this study was to develop a sensitive high-performance liquid chromatographic (HPLC) method for the detection and estimation of the camptothecin concentration in biological fluids. Using HPLC coupled with fluorescence detection, at an excitation wavelength of 370 nm and an emission wavelength of 434 nm, we found that the lower limits of detection for camptothecin in aqueous, plasma and urine samples were 0.5, 1 and 10 ng/ml, respectively. The ideal mobile phase used was methanol-10 mM potassium phosphate (75:25, v/v, pH 4.0). To determine the utilization of the method in a biological system, we studied the pharmacokinetics of camptothecin in mice. Elimination of camptothecin from mice blood was triphasic and followed first-order kinetics. The half-life of camptothecin in mouse blood was 25.7 min. Our studies indicate that HPLC with fluorescence detection for the determination of camptothecin in different media is a simple, rapid, sensitive and reproducible method.