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31.
Novel method for in-situ surfactant-based solid-phase extraction: application to the determination of Co(II) and Ni(II) in aqueous samples 总被引:1,自引:0,他引:1
We report on a completely new kind of solid phase extraction which we term in-situ surfactant-based solid-phase extraction (ISS-SPE). It represents a simple and rapid method for extraction from aqueous samples and preconcentration of compounds containing hydrophobic (alkyl) groups. A cationic surfactant containing alkyl chain is dissolved in the aqueous sample. Following the addition of hexafluorophosphate (HFP; an ion-pairing anion), solutions turn cloudy due to the interaction between the surfactant and the HFP ion. This is due to the formation of fine solid particles composed of the HFP salt of the cationic surfactant. The alkyl groups of the surfactant in the solid particles strongly interact with hydrophobic groups of analytes and become bound. The solid particles are centrifuged, and the sedimented particles can be either dissolved in an appropriate organic solvent, or leached with a solvent to recover the absorbed analyte(s). The method presented here has distinct advantages in that the extraction times are short and recoveries are high, probably a result of the formation of very fine particles of large specific surface, and of their good dispersion in the sample solution. The performance of ISS-SPE was demonstrated by extracting chelates of Co(II) and Ni(II) from water samples. Under the optimized conditions, the preconcentration factors are 51 and 45, respectively, and the detection limits are 0.9 and 0.6???g?L?1. The method was validated by the analysis of a certified reference material and by comparing results with those obtained by electrothermal AAS. Figure
In ISS-SPE method, a cationic surfactant containing alkyl chain is dissolved in aqueous sample. After addition of hexafluorophosphate anion, a cloudy solution is formed due to formation of fine solid particles (surfactant hexafluorophosphate salt). Hydrophobic anaytes can be adsorbed on the alkyl group of the solid particles and extracted. 相似文献
32.
Amirhossein Hajihosseini Farzaneh Maleki Gholam Reza Rokni Lamooki 《Chaos, solitons, and fractals》2011,44(11):1004-1019
A class of recurrent neural networks is constructed by generalizing a specific class of n-neuron networks. It is shown that the newly constructed network experiences generic pitchfork and Hopf codimension one bifurcations. It is also proved that the emergence of generic Bogdanov–Takens, pitchfork–Hopf and Hopf–Hopf codimension two, and the degenerate Bogdanov–Takens bifurcation points in the parameter space is possible due to the intersections of codimension one bifurcation curves. The occurrence of bifurcations of higher codimensions significantly increases the capability of the newly constructed recurrent neural network to learn broader families of periodic signals. 相似文献
33.
The electrooxidation of hydrochlorothiazide (HCT) at the surface of a benzoylferrocene modified multi-walled carbon nanotube paste electrode was studied using electrochemical approaches. Under the optimized conditions (pH 7.0), the square wave voltammetric peak current of HCT increased linearly with HCT concentration in the ranges of 6.0?×?10?7 to 3.0?×?10?4 M. The detection limit was 9.0?×?10?8 M HCT. The diffusion coefficient (D?=?1.75?×?10?5 cm2/s) and electron transfer coefficient (α?=?0.45) for HCT oxidation were also determined. The proposed sensor was successfully applied for the determination of HCT in human urine and tablet samples. 相似文献
34.
Aliyari Elnaz Fathi Ali Akbar Alvand Mahrouz Jamshidi Parastoo Shemirani Farzaneh Mozaffari Shahla Neyestani Mahmoud Reza 《Research on Chemical Intermediates》2021,47(5):1905-1918
Research on Chemical Intermediates - This article presents an ultrasound-assisted dispersive magnetic solid-phase extraction method (USA-DMSPE) to preconcentration Cd(II) and Pb(II) simultaneously.... 相似文献
35.
Tonya Vitova Radmila Faizova Jorge I. Amaro-Estrada Laurent Maron Tim Pruessmann Thomas Neill Aaron Beck Bianca Schacherl Farzaneh Fadaei Tirani Marinella Mazzanti 《Chemical science》2022,13(37):11038
The stabilization of uranyl(v) (UO21+) by Fe(ii) in natural systems remains an open question in uranium chemistry. Stabilization of UVO21+ by Fe(ii) against disproportionation was also demonstrated in molecular complexes. However, the relation between the Fe(ii) induced stability and the change of the bonding properties have not been elucidated up to date. We demonstrate that U(v) – oaxial bond covalency decreases upon binding to Fe(ii) inducing redirection of electron density from the U(v) – oaxial bond towards the U(v) – equatorial bonds thereby increasing bond covalency. Our results indicate that such increased covalent interaction of U(v) with the equatorial ligands resulting from iron binding lead to higher stability of uranyl(v). For the first time a combination of U M4,5 high energy resolution X-ray absorption near edge structure (HR-XANES) and valence band resonant inelastic X-ray scattering (VB-RIXS) and ab initio multireference CASSCF and DFT based computations were applied to establish the electronic structure of iron-bound uranyl(v).The role of Fe in the increased stability of uranyl(v) is clarified by using state of the art uranium metalorganic chemistry, advanced X-ray spectroscopic approaches and computations. 相似文献
36.
37.
JPC – Journal of Planar Chromatography – Modern TLC - A new stability-indicating HPTLC assay has been established for leuprolide acetate. Silica gel 60F254 was used as stationary phase.... 相似文献
38.
Superhydrophobic and icephobic surfaces prepared by RF-sputtered polytetrafluoroethylene coatings 总被引:1,自引:0,他引:1
A superhydrophobic and icephobic surface were investigated on aluminum alloy substrate. Anodizing was used first to create a micro-nanostructured aluminum oxide underlayer on the alloy substrate. In a second step, the rough surface was coated with RF-sputtered polytetrafluoroethylene (PTFE or Teflon®). Scanning electron microscopy images showed a “bird's nest”-like structure on the anodized surface. The RF-sputtered PTFE coating exhibited a high static contact angle of ∼165° with a very low contact angle hysteresis of ∼3°. X-ray photoelectron spectroscopy (XPS) results showed high quantities of CF3 and CF2 groups, which are responsible for the hydrophobic behavior of the coatings. The performance of this superhydrophobic film was studied under atmospheric icing conditions. These results showed that on superhydrophobic surfaces ice-adhesion strength was 3.5 times lower than on the polished aluminum substrate. 相似文献
39.
Ohne Zusammenfassung 相似文献
40.
Encapsulation of fullerene into nanotubes based on a C2N sheet, known as nitrogenated holey graphene, was investigated using density functional theory. The structural and electronic properties of these carbon hybrid materials, consisting of nitrogenated holey nanotubes and a small C20 fullerene, were studied. The formation energies showed that encapsulation of the fullerene into the nitrogenated holey nanotube is an exothermic process. To characterise the electronic properties, the electronic band structure and density of states of armchair and zigzag nitrogenated holey nanotubes were calculated. Filling these nanotubes with the C20 fullerene resulted in a p-type semiconducting character. The energy band gap of the nitrogenated holey nanotubes decreased with fullerene encapsulation. The results are indicative of the possibility of band gap engineering by encapsulation of small fullerenes into nitrogenated holey nanotubes. 相似文献