H-point standard addition method for the selective simultaneous determination of nickel and copper using 1-(2-pyridylazo)-2-naphthol in Tween 80 micellar media.

The H-point standard addition method (HPSAM) has been applied for the simultaneous determination of nickel and copper in trace levels, using 1-(2-pyridylazo)-2-naphthol (PAN) as a chromogenic reagent in aqueous Tween 80 micellar media. Under the optimum condition, the simultaneous determinations of nickel and copper by HPSAM were performed. The absorbances at one pair of wavelengths, 548 and 579 nm, were monitored with the addition of standard solutions of copper. The method is able to accurately determine copper-to-nickel ratios of 15:1 to 1:10 (Wt/Wt). The effects of diverse ions on the determination of nickel and copper to investigate the selectivity of the method were also studied. The recommended procedure was successfully applied to some water and alloy samples.     

Spectrophotometric and AAS determination of trace amounts of cobalt after preconcentration by using alpha-benzilmonoxime-microcrystalline naphthalene.

The formed cobalt-a-benzilmonoxime complex was adsorbed onto microcrystalline naphthalene. Then it was determined by zero and first derivative spectrophotometry and by atomic absorption spectrophotometry (AAS) after dissolving into chloroform and methylisobutylketone (MIBK), respectively. Under optimum conditions, cobalt in the range of 1.0 - 20.0, 0.4 - 30.0 and 2.5 - 50.0 microg could be determined by spectrophotometry, first derivative spectrophotometry and AAS method, respectively. By the method, a preconcentration factor equal to approximately 30 for cobalt was obtained. The effect of diverse ions on the determination of 5.0 microg cobalt was also studied. The method was successfully applied to some pharmaceuticals and synthetic alloy samples.     

Chemical Constituents of the Essential Oil of <Emphasis Type="Italic">Nepeta oxyodonta</Emphasis>

Water-distilled essential oil from the aerial parts of Nepeta oxyodonta Boiss. was analyzed by GC/MS for the first time. Fifty-eight components were identified. The major components were (E)-caryophyllene (12.6%), spathulenol (8.5%), β-bourbonene (8.1%), germacrene-D (7.4%), α-cadinol (7.3%), germacrene-D-4-ol (6.8%), T-cadinol (5.6%), and caryophyllene oxide (5.3%).__________Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 141–142, March–April, 2005.     

Using a Natural Surfactant for Synthesize of NiO and CuO Nanostructures via Simple and Fast Microwave Approach

NiO and CuO nanostructures were synthesized successfully via simple and fast microwave approach. Olive oil was chose as surfactant for stabilizing nanostructures. Different parameters such as microwave time and power and olive oil concentration were investigated on product size and morphology. The products were characterized with X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrometry analysis.     

Two‐dimensional modeling for stability analysis of two‐phase stratified flow

The effect of wavelength and relative velocity on the disturbed interface of two‐phase stratified regime is modeled and discussed. To analyze the stability, a small perturbation is imposed on the interface. Growth or decline of the disturbed wave, relative velocity, and surface tension with respect to time will be discussed numerically. Newly developed scheme applied to a two‐dimensional flow field and the governing Navier–Stokes equations in laminar regime are solved. Finite volume method together with non‐staggered curvilinear grid is a very effective approach to capture interface shape with time. Because of the interface shape, for any time advancement, a new grid is performed separately on each stratified field, liquid, and gas regime. The results are compared with the analytical characteristics method and one‐dimensional modeling. This comparison shows that solving the momentum equation including viscosity term leads to physically more realistic results. In addition, the newly developed method is capable of predicting two‐phase stratified flow behavior more precisely than one‐dimensional modeling. It was perceived that the surface tension has an inevitable role in dissipation of interface instability and convergence of the two‐phase flow model. Copyright © 2009 John Wiley & Sons, Ltd.     

Potentiality of partial least-squares multivariate calibration in the spectrophotometric analysis of binary mixtures of purine bases

Abstract  

A partial least-squares (PLS) modeling was developed for the simultaneous spectrophotometric determination of adenine (AD) and guanine (GU). The determination of these analytes is pharmacologically necessary. Multivariate calibration is used because of spectral overlapping. The calibration set contained AD and GU in the concentration range of 1.4–20.3 and 1.5–25.7 μg cm⁻³, respectively. The absorption spectra were recorded from 200 to 300 nm. The predicted residual error sum-of-squares for AD and GU was 0.0500 and 0.4000 for number of principal components 3 and 2, respectively. The root mean square error of prediction for AD and GU was 0.0913 and 0.2582, respectively. The limits of detection were 0.02 and 0.03 μg cm⁻³ for AD and GU, respectively. The proposed method allows the simultaneous determination of AD and GU in spiked real matrixes of human urine, serum, and plasma.     

Three-dimensional dynamic Green’s functions for a multilayered transversely isotropic half-space

With the aid of a method of displacement potentials, an efficient and accurate analytical derivation of the three-dimensional dynamic Green’s functions for a transversely isotropic multilayered half-space is presented. Constituted by proper algebraic factorizations, a set of generalized transmission–reflection matrices and internal source fields that are free of any numerically unstable exponential terms are proposed for effective computations of the potential solution. Three-dimensional point-load Green’s functions for stresses and displacements are given, for the first time, in the complex-plane line-integral representations. The present formulations and solutions are analytically in exact agreement with the existing solutions given by Pak and Guzina (2002) for the isotropic case. For the numerical computation of the integrals, a robust and effective methodology which gives the necessary account of the presence of singularities including branch points and poles on the path of integration is laid out. A comparison with the existing numerical solutions for multilayered isotropic half-space is made to confirm the accuracy of the numerical solutions.     

A sensitive and simple extractive-spectrophotometric method for the determination of microgram amount of cobalt by using alpha-benzilmonoxime.

Alpha-benzilmonoxime has been used for the extraction and determination of cobalt at microgram amount. The reagent reacts with cobalt(II) in the pH range of 8.8 - 9.3 to form a yellow-color chelate, which is extracted in chloroform, toluene, and some other non-polar solvents. The chelate is stable in chloroform for about one day. Under the optimum conditions of the a-benzilmonoxime concentration and pH of 9.0, Beer's law was obeyed in the concentration range of 0.08 - 2.2 microg/ml cobalt. The molar absorptivity of the extracted species was 2.55 x 10(4) dm3/mol cm at 380 nm, with a detection limit of 0.01 microg/ml cobalt. Relative standard deviations of 0.4, 0.8 and 2.3% were found for the determination of cobalt concentrations of 2.2, 1.1 and 0.08 microg/ml, respectively. The effect of diverse ions on the determination of 1.00 microg/ml of cobalt has been studied. The method was applied to the determination of cobalt in vitamin B12 and B-complex ampoules, a Co2O3-Co3O4 laboratory chemical mixture and some synthetic alloy samples. The method is sensitive, simple, rapid and accurate.