Search results for " concentration"
showing 10 items of 1684 documents
Development of stir bar sorptive-dispersive microextraction mediated by magnetic nanoparticles and its analytical application to the determination of…
2014
A novel microextraction technique combining the principles of stir bar sorptive extraction (SBSE) and dispersive micro-solid phase extraction (DμSPE) is presented. The main feature of the method is the use of a neodymium-core stirring bar physically coated with a hydrophobic magnetic nanosorbent. Depending on stirring speed, the magnetic sorbent either acts as a coating material to the stir bar, thus affording extraction alike SBSE, or as a dispersed nanosorbent medium for the collection and extraction of the target analytes, in close analogy to DμSPE. Once the stirring process is finished, the strong magnetic field of the stir bar prevails again and rapidly retrieves the dispersed MNPs. Al…
Evaluation of solid-phase extraction and stir-bar sorptive extraction for the determination of fungicide residues at low-microg kg(-1) levels in grap…
2004
Abstract A liquid chromatography–mass spectrometry method has been developed for determining bitertanol, carboxin, flutriafol, pyrimethanil, tebuconazole and triadimefon. The evaluation of both atmospheric pressure interfaces (API), atmospheric pressure chemical ionization (APCI) and electrospray (ESI) using positive and negative ionization modes, clearly shows that the studied pesticides are more sensitive using APCI in positive mode. Two procedures based on solid-phase extraction (SPE) and stir-bar sorptive extraction (SBSE) have been assessed for extracting these compounds in grape. The recoveries obtained by SPE in samples spiked at the limit of quantification (LOQ) level ranged from 60…
Development and Optimization of Pre-Concentration Procedure of Rare-Earth Elements (REEs) in Their Minerals, Using Microwave - Assisted Sample Dissol…
2015
Abstract The aim of this research was to develop and optimize a procedure for determination of REEs in xenotime and monazite samples collected from Bangka Island, which were compared to Standard Monazite (71 AG) of Bureau of Analyzed Samples, London. ICP-OES method was used for the determination. The samples were dried and sterilized by heating for a week at 110 °C, before digesting with nitric acid and hydrofluoric acid, using a microwave-assisted digestion system. After a careful line selection, at the detection limits for all REEs in the ng/mL the REEs were reliably obtained at the 0.09 – 38% level.
Separation of plasma membrane proteins of cultured human fibroblasts by affinity chromatography on bonded microparticulate silicas.
1984
Abstract Adsorbents for high-performance affinity chromatography were prepared by bonding proteins and reactive Procion triazine dyes to 3-isothiocyanatopropyl- and 3-aminopropylsilicas. The materials prepared were used successfully in the separation of hydrophobic plasma membrane proteins of cultured human fibroblasts. The data obtained show that the reaction of 3-isothiocyanatopropyltriethoxysilane (ITCPS) with the surface hydroxyl groups of silica yields a new and convenient route to preparing an “activated carrier” that is capable of coupling with potential affinity ligands containing amino functional groups. The reaction and bonding procedures of 3-isothiocyanatopropyltriethoxysilane a…
The importance of a highly active and DeltapH-regulated diatoxanthin epoxidase for the regulation of the PS II antenna function in diadinoxanthin cyc…
2005
The present study focuses on the regulation of diatoxanthin (Dtx) epoxidation in the diadinoxanthin (Ddx) cycle containing algae Phaeodactylum tricornutum, Thalassiosira pseudonana, Cyclotella meneghiniana and Prymnesium parvum and its significance for the control of the photosystem II (PS II) antenna function. Our data show that Dtx epoxidase can exhibit extremely high activities when algal cells are transferred from high light (HL) to low light (LL). Under HL conditions, Dtx epoxidation is strongly inhibited by the light-driven proton gradient. Uncoupling of the cells during HL illumination restores the high epoxidation rates observed during LL. In Ddx cycle containing algae, non-photoche…
Über die verdünnungsentropie der lösungen von fadenmolekülen
1953
Es wird versucht, auf breiter experimenteller Basis, einen allgemeinen uberblick uber die Wechselwirkung zwischen Polymeren und Losungsmitteln (LM) in masigen Konzentrationen (bis 3%) zu gewinnen. Zu diesem Zweck wird der osmotische Druck in Abhangigkeit von der Konzentration und der Temperatur fur 2 verschiedene Polymere in einer groseren Anzahl von Losungsmitteln gemessen und daraus die Virialkoeffizienten und die thermodynamischen Funktionen Δμ1, Δh1 und Δs1 berechnet. Der 1. Virialkoeffizient (VK) A hangt, wie zu erwarten war, nur vom Molekularge which des Polymeren ab. Der 2. und der 3. VK werden in der Grose B zusammengefast, die ein Mas fur die „Gute” des LM ist. Die differentielle V…
Resonant Photoelectron Diffraction
2013
A layout of a resonant photoelectron diffraction, RESPED, experiment is described from the theoretical basis to the data acquisition and analysis procedures. The theory of the resonance between the directly emitted photoelectron of a selected valence band and the electron emitted by autoionization (Auger) of the same valence band is presented within a formal frame. The critical issue of the angular symmetry and distribution of the resonating electron is discussed in connection with the current computational protocols for photoelectron diffraction, PED, analysis. A few representative applications are presented, where RESPED is shown to overcome some limitations of conventional PED thanks to …
NUMERICAL-EXPERIMENTAL METHOD FOR THE ANALYSIS OF RESIDUAL STRESSES IN COLD-EXPANDED HOLES
2012
Hole cold expansion is a technique widely used to improve the fatigue life of components with holes, e.g. bolted or riveted joints. As it has been demonstrated in literature by analytical, numerical and experimental analyses carried out by several authors, the compressive residual stresses introduced by the hole cold expansion have a beneficial influence on both the static and the fatigue strength of the treated component, because they reduce significantly the typical stress peaks around the hole due to stress concentration. In the literature, various analyses of the residual stresses introduced by the hole cold expansion have been performed by using several methods such as X-ray diffractio…
Influence of mechanoactivation on the adhesion and mechanical properties of metal/oxide interfaces
2005
Properties of interfaces in solid state metal/oxide joints (Al/SiO2, Al/MgO, Al/glass, Mg/MgO, In/glass, Mg/SiO2 etc.) are reported. Interfaces were formed at plastic deformation of metal on the oxide surface at room temperature. Structure, composition, and micromechanical properties of the interfaces are studied by AFM, X-ray diffraction, SIMS, electron, optical microscopy, and precision microindentation. A noticeable adhesion is observed in the regions of maximum shear strain in case of metals with low oxide formation energy. Formation of a reaction zone with oxygen concentration gradient is detected in which the metal near the interface hardens. The effect of mechanoactivation is conside…
Synthesis of single crystalline sub-micron rutile TiO2 rods using hydrothermal treatment in acidic media
2014
Size engineered rutile sub-micron rods were obtained from nanostructured titania under acidic conditions. The synthesis was performed by hydrothermal treatment starting from TiO2-P25 and HCl. The synthesis proceeds in less than two hours and can be up-scaled to several grams in a one-pot reaction by increasing the reaction time. The product is single-phase, and the particles are single crystalline as confirmed by electron diffraction and powder X-ray diffraction analysis. The length of the particles can be varied over a wide range from 100 nm to 1.3 μm by changing the acid concentration. Particle growth is proposed to proceed by a dissolution-recrystallization process via soluble [TiCl6]2− …