Optimized Ultrasonic Extraction for the Determination of Polyaromatic Hydrocarbons by Gas Chromatography–Mass Spectrometry

The presence of polycyclic aromatic hydrocarbons (PAHs) in soil is an issue of concern due to their harmful effects on human health. The goal of this study was to optimize ultrasonic extraction to establish an efficient, easy, and low-cost method for the determination of 16 priority PAHs in soil. The time of extraction and solvent systems were optimized with the analysis by gas chromatography–mass spectrometry. The method was validated, and the optimum results were obtained using 1:1 cyclohexane:acetone and 1:1 hexane:acetone solvent systems with 30- and 60-min sonication times.     

Anti-plane shear cracks in ideally plastic crystals

Cracks in ductile single crystals are analyzed here for geometries and orientations such that two-dimensional states of anti-plane shear constitute possible deformation fields. The crystals are modelled as ideally plastic and yield according to critical resolved shear stresses on their slip systems. Restrictions on the asymptotic forms of stress and deformation fields at crack tips are established for anti-plane loading of stationary and quasistatically growing cracks, and solutions are presented for several specific orientations in f.c.c. and b.c.c. crystals. The asymptotic solutions are complemented by complete elastic-plastic solutions for stationary and growing cracks under small scale yielding, based on previous work by Rice (1967, 1984) and Freund (1979). Remarkably, the plastic zone at a stationary crack tip collapses into discrete planes of displacement and stress discontinuity emanating from the tip; plastic flow consists of concentrated shear on the displacement discontinuities. For the growing crack these same planes, if not coincident with the crack plane, constitute collapsed plastic zones in which velocity and plastic strain discontinuities occur, but across which the stresses and anti-plane displacement are fully continuous. The planes of discontinuity are in several cases coincident with crystal slip planes but it is shown that this need not be the case, e.g., for orientations in which anti-plane yielding occurs by multi-slip, or for special orientations in which the crack tip and the discontinuity planes are perpendicular to the activated slip plane.     

Formation of nanosize Li-ferrites from acetylacetonato complexes and their crystal structure, microstructure and order–disorder phase transition

Nanosize Li-ferrites were synthesised by the thermal decomposition of an appropriate mixture of complex compounds with acetylacetone - (2,4 pentadione) ligands ([M(AA)_x]; M=Li and Fe) at 500 °C. The obtained sample is composed of three phases determined by the standard Rietveld procedure: Li_0.5Fe_2.5O₄ (S.G. P4₃32), Li_1.16Fe₃O₄ (S.G. Fd 3̄ m) and LiFeO₂ (S.G. Fm 3̄ m). Cation distribution in nanosize ordered spinel Li_0.5Fe_2.5O₄ deviates from that of the bulk counterpart. Microstructure parameters (crystallite size of ∼23 nm and strain of 3.2526(9)×10³) were determined by the Rietveld refinement of the TCH-pV parameters. SEM microphotographs show a particle size of ∼50–60 nm. An order–disorder phase transition in ordered spinel Li_0.5Fe_2.5O₄was studied by DSC measurements and in situ XRPD technique.The temperature of phase transition was found to be 762 °C (DSC) and (±) 7455°C.(XRPD)PACS 81.07.Bc; 81.16.Be; 61.66.Fn; 61.50.Ks     

Sensitive flow-injection amperometric detection of iodide using Mn3+ and As3+.

A rapid, selective, and sensitive kinetic flow-injection method for iodide content determination with amperometric detection on a platinum electrode was developed. The method is based on the catalytic effect of iodide on the Mn3+ reaction with As3+ in the presence of sulfuric acid. The calibration curve was linear in the concentration range from 5.0 x 10(-7) to 1.0 x 10(-4) mol/L iodide. The limit of detection (LOD) was found to be 5.0 x 10(-9) mol/L iodide. The relative standard deviations (RSD) were 1.68% and 3.03% for 1.0 x 10(-3) mol/L standard and 1.0 x 10(-6) mol/L iodide solution (n = 6), respectively. The method has been successfully applied for determination of iodide in waters, table salts, fodder, organic substances and human blood sera. The results were compared with those obtained by a standard AOAC (Association of Official Analytical Chemists) method, as well as with those obtained by a kinetic spectrophotometric procedure for determination of iodide.     

Technical and radiological characterisation of fly ash and bottom ash from thermal power plant

Journal of Radioanalytical and Nuclear Chemistry - Huge quantities of fly ash and bottom ash are generated from thermal power plants and it presents great concern for country, mainly due...     

Activity-guided isolation of novel norwithanolides from depreasubtriflora with potential cancer chemopreventive activity

Activity-monitored fractionation of a CHCl(3)-soluble extract of Deprea subtriflora using a quinone reductase induction assay led to the purification of subtrifloralactones A-J (1-10), 10 novel C-18 norwithanolides based on a new C(27) skeleton. These compounds were characterized by spectroscopic and chemical studies, and single-crystal X-ray diffraction analysis was used to confirm the structures of 1 and 4. Compounds 1-10 were evaluated for their cancer chemopreventive activity in terms of their ability to induce quinone reductase activity with cultured murine hepatoma cells, and compounds 1 and 6 were found to be highly effective.     

Physical investigation of the colloidal iron-inulin complex

The iron-inulin complex, which could be applied as a parenteral hematinic agent, is studied by physical techniques. Electron microscopy shows that the complex contains very small particles that are approximately spherical and 10–30 nm in diameter. The examination reveals the presence of an electron-transparent sheath, probably consisting of linked inulin oligomers with M _w ∼ 3000 g mol⁻¹, around the electron-dense, ironcontaining core of the FeOOH particles. FTIR spectroscopy suggests the existence of stronger hydrogen bonds, which are formed in the complexes between FeOOH and oligosaccharides, compared to the hydrogen bond in the initial compounds. A gel filtration technique on a Sephadex column showed conclusively that a large proportion of combined inulin oligomers with M _w ∼ 1500 g mol⁻¹ as secondary fractions are present in complexes. These low-molecular-weight inulin fractions have a significant influence on the complex stability. The text was submitted by the authors in English.     

Identification of photocatalytic degradation products of diazinon in TiO2 aqueous suspensions using GC/MS/MS and LC/MS with quadrupole time-of-flight mass spectrometry

The photocatalytic degradation of the organophosphorus insecticide diazinon in aqueous suspensions has been studied by using titanium dioxide as a photocatalyst. The degradation of the insecticide was a fast process and included the formation of several intermediates that were identified using GC/ion-trap mass spectrometry with EI or CI in positive and negative ionization mode and HPLC/electrospray-QqTOF mass spectrometry. Since primarily hydroxy derivatives were identified in these aqueous suspensions, the mechanism of degradation was probably based on hydroxyl radical attack. The initial oxidative pathways of the degradation of diazinon involved the substitution of sulfur by oxygen on the Pz.dbnd6;S bond, cleavage of the pyrimidine ester bond, and oxidation of the isopropyl group. Exact mass measurements of the derivatives allowed the elemental formula of the molecules to be determined confidently. Similarities to the metabolic pathways occurring in living organisms were observed.