Search results for "chemistry [Water]"
showing 10 items of 2369 documents
A capillary liquid chromatography method for benzalkonium chloride determination as a component or contaminant in mixtures of biocides
2015
A method for quantifying benzalkonium chloride (BAK), an alkyl dimethyl benzyl ammonium compound, in several biocides formulations is proposed. A tertiary amine like N-(3-aminopropyl)-N-dodecyl-1,3-propanediamine (TA) and a straight-chain alkyl ammonium compound like trimethyl-tetradecyl ammonium chloride (TMTDAC), have been employed as trade surfactants besides BAK. Two capillary analytical columns with different polarities are tested: inertsil CN-3 capillary column (150mm×0.5mm i.d., 3μm particle diameter) and a non endcapped Zorbax C18 capillary column (35mm×0.5mm i.d., 5μm particle diameter). This latter column provided the best separation of the BAK homologues in less than 12min using …
Sample Preparation Improvement in Polycyclic Aromatic Hydrocarbons Determination in Olive Oils by Gel Permeation Chromatography and Liquid Chromatogr…
2005
Abstract The determination of 15 polycyclic aromatic hydrocarbons (PAHs) in olive oil samples has been improved in order to obtain a fast methodology with a low limit of detection through the combination of liquid–liquid extraction with acetonitrile and preparative gel permeation chromatography (GPC) prior to the injection of purified extracts into a C18 column. Acetonitrile–water was used as the mobile phase with a gradient from 50 to 95%, w/w, acetonitrile in 30 min. The oven temperature was maintained at 15°C, and fluorometric detection was made at a fixed excitation wavelength of 264 nm and variable, optimal emission wavelength for each analyte ranging from 352 nm for 11-H-benzo(b)fluor…
Thermal stability of transition alumina nanocrystals with different microstructures
2018
Abstract The preparation of well-crystallized boehmite nanoparticles with different morphologies, encompassing from aciculae or rods of 320, 150 and 70 nm of length to platelets of 50 nm in diameter, allowed a comparative study of their respective thermal evolutions as alumina precursors. Static thermal treatments of boehmite nanocrystals at 600, 1000 and 1200 °C and a dynamic, in situ synchrotron study between 100 and 1000 °C revealed that original boehmite microstructures, i.e. size and shape of the nanoparticles, were kept not only in γ-Al 2 O 3 but also in transitional aluminas up to 1000 °C. Specifically, at that temperature, acicular samples presented θ-Al 2 O 3 structure, while in pl…
The Bi sulfates from the Alfenza Mine, Crodo, Italy: An automatic electron diffraction tomography (ADT) study
2014
We report about three bismuth sulfates from mineralized quartz dikes from Alfenza (Crodo, Italy), two new phases and a rare mineral, cannonite, all growing on bismuthinite. The first new phase occurs as white, "hortensia-like" aggregates of pseudo-hexagonal platelets, with perfect basal cleavage, similar to 20 mu m wide and few micrometers thick. The approximate composition is Bi2O2(SO4), and cell parameters and symmetry, as determined by automatic diffraction tomography, are a = 22.0(4), b = 16.7(3), c = 15.9(3) angstrom, beta = 102.9(5)degrees, space group Pc or P2/c. A major stacking disorder is detected by HR-SEM images and electron diffraction data.The second new phase was detected onl…
Ferro-pedrizite, NaLi2(Fe2+ 2Al2Li)Si8O22(OH)2, a new amphibole-supergroup mineral from the Sutlug pegmatite, Tyva Republic, Russia
2015
Ferro-pedrizite, a new amphibole-supergroup mineral was discovered in the Sutlug pegmatite occurrence situated in the Targi River Basin, Tyva Republic, Eastern Sibera, Russia. The associated minerals are quartz, albite, microcline, spodumene, cassiterite, beryl, columbite-(Mn), fergusonite-β-(Y), fluorapatite, schorl, trilithionite and fluorite. Ferro-pedrizite forms dark grey-blue to violet-blue acicular and long prismatic crystals up to 2 × 5 × 50 mm and their aggregates. D meas = 3.16(1) g/cm3 (by hydrostatic weighing), 3.13(1) g/cm3 (by flotation in heavy liquids); D calc = 3.135 g/cm3. Ferro-pedrizite is optically biaxial (−), α = 1.614(3), β = 1.638(3), γ = 1.653(3), 2 V meas = 75(5)°…
Assessment of the mechanism of elemental incorporation into bivalve shells (Arctica islandica) based on elemental distribution at the microstructural…
2014
Abstract To address the mechanism of elemental incorporation into shells of the bivalve Arctica islandica , we performed two-dimensional elemental mapping of Sr, Mg, and S at a ∼3 μm spatial resolution using electron microprobe. These elemental distributions were precisely compared to the shell microstructure. The Sr distribution was intimately linked to the S concentration and/or shell microstructure. Sr showed a clear annual pattern with higher values at the annual growth lines and lower values in annual growth increments. The Sr and S concentrations were higher near sub-annual growth lines than in the adjacent regions, which were dominated by acicular microstructure (middle shell layer) …
Geochemistry of REE, Zr and HF in a wide range of pH and water composition: The Nevado del Ruiz volcano hydrothermal system (Colombia)
2015
International audience; The geochemical behaviour of Rare Earth Elements, Zr and Hf was investigated in the thermal waters of Nevado del Ruiz volcano system. A wide range of pH, between 1.0 and 8.8, characterizes these fluids. The acidic waters are sulphate dominated with different Cl/SO4 ratios. The important role of the pH and the ionic complexes for the distribution of REE, Zr and Hf in the aqueous phase was evidenced. The pH rules the precipitation of authigenic Fe and Al oxyhydroxides producing changes in REE, Zr, Hf amounts and strong anomalies of Cerium. The precipitation of alunite and jarosite removes LREE from the solution, changing the REE distribution in acidic waters.Y–Ho and Z…
Interpretive search of optimal isocratic and gradient separations in micellar liquid chromatography in extended organic solvent domains
2020
Abstract Micellar liquid chromatography (MLC) is a reversed-phase mode with mobile phases containing an organic solvent and a micellised surfactant. Most procedures developed in MLC are implemented in the isocratic mode, since the general elution problem in chromatography is less troublesome. However, gradient elution may be still useful in MLC to analyse mixtures of compounds within a wide range of polarities, in shorter times. MLC using gradients is attractive to determine by direct injection moderate to low polar compounds in physiological samples. In these analyses, the use of initial micellar conditions (isocratic or gradient) with a fixed amount of surfactant above the critical micell…
A Novel Deep Learning Stack for APT Detection
2019
We present a novel Deep Learning (DL) stack for detecting Advanced Persistent threat (APT) attacks. This model is based on a theoretical approach where an APT is observed as a multi-vector multi-stage attack with a continuous strategic campaign. To capture these attacks, the entire network flow and particularly raw data must be used as an input for the detection process. By combining different types of tailored DL-methods, it is possible to capture certain types of anomalies and behaviour. Our method essentially breaks down a bigger problem into smaller tasks, tries to solve these sequentially and finally returns a conclusive result. This concept paper outlines, for example, the problems an…
Numerical approach to problems of gravitational instability of geostructures with advected material boundaries
1998
SUMMARY We present a numerical approach for solving 2-D mantle flow problems where the chemical composition changes abruptly across intermediate boundaries. The method combines a Galerkin-spline technique with a method of integration over regions bounded by advected interfaces to represent discontinuous variations of material parameters. It allows direct approximation of a natural free surface position, instead of a posteriori calculation of topography from the normal stress at the upper free-slip boundary. We formulate a model where a viscous incompressible fluid filling a square box is divided into layers (not necessarily horizontal) by advected boundaries, across which the density and vi…