Flame atomic absorption determination of palladium in solutions after preconcentration using octadecyl silica membrane disks modified by thioridazine.HCl

A new simple and reliable method for rapid and selective extraction and determination of trace level of Pd(II) ion is developed. Palladium ions are adsorbed quantitatively during passage of aqueous samples through octadecyl silica membrane disks modified with thioridazine·HCl (TRH). The influence of flow rates of eluent and sample solution, amount of ligand, types and least amount of eluent, and pH of samples were studied. Almost all matrix elements were found to pass through the disk to drain. Break through volume and limit of detection of the membrane disks modified by 5 mg of TRH was found to be 1.0 l and 12 μg l⁻¹, respectively. The retained Pd(II) ions are then stripped from the disk with a minimal amount of sulfite solution as eluent and subsequently measured by atomic absorption spectrometry. The proposed method permitted large enrichment factors of about 100 and higher. The method was applied to the recovery of Pd(II) ions from different industrial samples and waters.     

Polymerization of lanthanide acrylonitrile complexes

The molecular complexes of some lanthanides scandium (Sc3+), yttrium (Y3+), lanthanum (La3+), gadolinium (Gd3+), cerium (Ce3+) and ytterbium (Yb3) have been studies in dimethyl formamide (DMF) spectrophtometrically equilibrium constants (K), molar extintion coefficient (epsilon), energy of transition (E) and free energy (delta G*) were calculated. The polymerization of acrylonitrile has been studied and investigated in the presence of Sc3+, Y3+, La3+, Gd3+, Ce3+, and Yb3+ ions. The IR spectra of the formed AN-M (III) Br3 polymer complexes show the absence of the C identical to N band and the presence of two new bands corresponding to NH2 and OH groups. Magnetic moment values and the thermal stabilities of homopolymer and the polymer complexes were studied by means of thermogravimetric analysis and the activation energies for degradation were calculated.     

Ion-selective electrode for the determination of prenalterol

A new prenalterol (Pr) ion-selective PVC membrane electrode based on the ion-pair complex of Pr with sodium tetraphenylborate was prepared and its performance characteristics were studied. The electrode exhibited a linear response with a good Nernstian slope over a relatively wide range of concentration. The electrode whose membrane was made of 8.0% (w/w) of ion pair, 49.5% (w/w) of dioctyl phthalate (DOP) and 43.5% (w/w) of PVC showed characteristics higher than those obtained with the other ones, namely, slope of 56.3 mV per concentration decade, at 25 °C; usable concentration range 1.2×10⁻⁵–3.2×10⁻² M prenalterol; response time ≤20 s. Up to 24 h continuous soaking, the calibration graph slope was constant at 56.0 mV per concentration decade, at 25 °C, then it decreased gradually as the time of soaking increases reaching 41 mV per decade after 11 days. The changes in pH did not affect the electrode performance within the range 2.2–7.5. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the electrode. The electrode showed very good selectivity for Pr with respect to a large number of inorganic and organic cations. The standard addition method and potentiometric titration were used to determine Pr in pure solutions and in pharmaceutical formulations. The relative standard deviations (R.S.D.) of the three methods used for the determination of prenalterol in pharmaceutical formulations were 0.8, 2.1 and 1.9% of the extrapolation, standard addition and potentiometric methods, respectively.     

Colorimetric Microdetermination of Bromhexine Drug in Aqueous Solution

A simple, accurate and sensitive method for determination of bromhexine hydrochloride drug in aqueous solution has been described. The procedure has been based on the reaction of this drug with an excess amount of p‐dimethylaminobenzaldehyde (DAB) in acidic medium (pH =1.6) and the presence of sodium dodecyl sulfate (SDS). The produced yellow color from this reaction has been followed spectrophotometrically at an absorbance maximum of 430 nm. Microgram amounts of bromhexine hydrochloride can be estimated with an accuracy of better than ±1.5% and a relative standard deviation of less than 3.5%. The method has been used for the determination of 0.41–82.5 μg.mL^?1 with a molar extinction coefficient of 4699.1–3602.3 L.mol^?1.cm^?1. An application of the developed procedure to bulk bromhexine hydrochloride and some of its pharmaceutical preparations has been carried out. The effect of the presence of some other surfactants and common pharmaceutical additives has been investigated. A comparison of the presented method with that in the absence of SDS and the standard method of the British Pharmacopoeia has been explored. The suggestion, according to the results, is to use the developed method as standard in pharmaceutical applications.     

Infrared study of the effect of some solvents on the structural properties of soybean proteins

The effect of three groups of solvents classified according to their water miscibility on soybean proteins at 80°C and 100°C was investigated by following the changes in their infrared spectra. The results showed that, for immiscible solvents, the values of the absorbances ratios

Formation and characterization of high surface area thermally stabilized titania/silica composite materials via hydrolysis of titanium(IV) tetra-isopropoxide in sols of spherical silica particles

A direct synthetic route leading to titania particles dispersed on nonporous spherical silica particles has been investigated; 5, 10, and 20% (w/w) titania/silica sols mixtures were achieved via hydrolyzation of titanium tetra-isopropxide solution in the mother liquor of a freshly prepared sol of spherical silica particles (St?ber particles). Titania/silica materials were produced by subsequent drying and calcination of the xerogels so obtained for 3 h at 400 and 600 degrees C. The materials were investigated by means of thermal analyses (TGA and DSC), FT-IR, N(2) gas adsorption-desorption, powder X-ray diffraction (XRD), and transmission electron microscopy (TEM). In spite of the low surface area (13.1 m(2)/g) of the pure spherical silica particles calcined at 400 degrees C, high surface area and mesoporous texture titania/silica materials were obtained (e.g., S(BET) ca. 293 m(2)/g for the 10% titania/silica calcined at 400 degrees C). Moreover, the materials were shown to be amorphous toward XRD up to 600 degrees C, while reasonable surface areas were preserved. It has been concluded that dispersion of titania particles onto the surface of the nonporous spherical silica particles increase their roughness, therefore leading to composite materials of less firm packing and mesoporosity.     

Infrared matrix isolation evidence for the formation of (η5-cyclopentadienyl)tricarbonyl-molybdenum and -tungsten radicals in carbon monoxide matrices at 12 K

Infrared spectroscopic evidence including ¹³CO labelling and energy-factored force-field fitting is presented for the first time to show that the radicals (η⁵-C₅H₅)-M(CO)₃^? (M = MO, W) and HCO are produced on photolysis of (η⁵-C₅H₅)M(CO)₃H complexes in CO matrices at 12 K.     

Simultaneous determination of U and Th by delayed fission neutron technique based on neutron generator

A method for simultaneous determination of uranium and thorium based on the deviation of their fission cross-section curves has been developed. Using a D-T neutron generator two different neutron spectra were produced with and without moderator around the target. The detection limits were found to be 0.044 mg and 0.25 mg in the presence of a moderator, while for fast neutrons 0.017 mg and 0.037 mg for uranium and thorium, respectively.This work was supported in part by the Ministry of Higher Education and the Hungarian Academy of Sciences.     

Initial observation of magnetization hysteresis and quantum tunneling in mixed manganese-lanthanide single-molecule magnets

The preparation of a new family of mixed transition metal/lanthanide clusters is reported. The reaction of [Mn3O(O2CPh)6(py)2(H2O)] with Ln(NO3)3 (Ln = Nd, Gd, Dy, Ho, and Eu) in a 1:2 molar ratio in MeOH/MeCN (1:20 v/v) leads to dark crystals in 55-60% isolated yield of complexes all containing the [Mn11Ln4]45+ core. The Dy compound has been found to give out-of-phase AC susceptibility signals, suggesting it might be a single-molecule magnet (SMM). This was confirmed by the observation of magnetization hysteresis loops. An Arrhenius plot constructed from magnetization decay data gave a barrier to relaxation of 9.3 K and showed the temperature-independent relaxation at very low temperatures indicative of quantum tunneling of magnetization. This is the initial demonstration of hysteresis and quantum behavior in a mixed 3d/4f SMM.     

Parallel nucleic acid recognition by the LNA (locked nucleic acid) stereoisomers beta-L-LNA and alpha-D-LNA; studies in the mirror image world

Two LNA (locked nucleic acid) stereoisomers (beta-L-LNA and alpha-D-LNA) are evaluated in the mirror-image world, that is by the study of two mixed sequences of LNA and alpha-L-LNA and their L-DNA and L-RNA complements. Both are found to display high-affinity RNA-recognition by the formation of duplexes with parallel strand orientation.