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991.
The paper presents a new method based on simultaneous derivatization and air-assisted liquid–liquid microextraction (AALLME) for the extraction and preconcentration of some aliphatic amines prior to gas chromatography-flame ionization detection (GC-FID). Primary aliphatic amines are derivatized and extracted simultaneously by a fast reaction with butylchloroformate (derivatization agent/extraction solvent) under mild conditions. The mixture of butylchloroformate and aqueous sample solution is rapidly sucked into a 10-mL glass syringe and then is injected into a test tube with conical bottom and the procedure is repeated seven times. After centrifuging the resulted cloudy solution, the derivatized analytes in the sedimented phase are determined by GC-FID. The influence of main factors on the efficiency of derivatization/extraction procedure is studied. Under the optimal conditions, the enrichment factors (EFs) for aliphatic amines are obtained in the range of 248–360 and limits of detection (LODs) are between 0.30 and 2.6 μg L−1. The obtained extraction recoveries ranged from 50 to 72% and the relative standard deviation (RSD) was less than 4.8% for intra-day (n = 6) and inter-days (n = 4) precision. The method is successfully applied to determine some aliphatic amines in environmental water samples. 相似文献
992.
Abbas Afkhami Farzaneh Soltani-Felehgari Tayyebeh Madrakian Hamed Ghaedi Majid Rezaeivala 《Analytica chimica acta》2013
A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, selective and highly sensitive simultaneous determination of cadmium, copper and mercury using square wave anodic stripping voltammetry (SWASV). The carbon paste electrode was modified by N,N′-bis(3-(2-thenylidenimino)propyl)piperazine coated silica nanoparticles. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, −1.100 V vs. Ag/AgCl; deposition time, 60 s; resting time, 10 s; SW frequency, 25 Hz; pulse amplitude, 0.15 V; dc voltage step height, 4.4 mV), the detection limit was 0.3, 0.1 and 0.05 ng mL−1 for the determination of Cd2+, Cu2+ and Hg2+, respectively. The complexation reaction of the ligand with several metal cations in methanol was studied and the stability constants of the complexes were obtained. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective for the simultaneous determination of Cd2+, Cu2+ and Hg2+. Furthermore, the present method was applied to the determination of Cd2+, Cu2+ and Hg2+ in water and some foodstuff samples. 相似文献
993.
Nádia R. Aguiam Vânia I. CastroAna I.F. Ribeiro Rui D.V. FernandesCarina M. Carvalho Susana P.G. CostaSílvia M.M.A. Pereira-Lima 《Tetrahedron》2013
The multicomponent Ugi reaction is a straightforward method that can be used for the synthesis of highly hindered C-tetrasubstituted amino acids by reacting an amine, a ketone or aldehyde, a carboxylic acid and an isocyanide. In the present work, the synthesis of several α,α-dialkylglycines (α,α-diethylglycine, Deg; α,α-dipropylglycine, Dpg; 1-amino-1-cyclohexanecarboxylic acid, Ac6c) was achieved by solid phase Ugi reaction using resins functionalized with the isocyanide group. Since no resins with these features were available commercially, the functionalization of an aminomethylated resin started by the use of glycine (Gly), β-alanine (β-Ala) and γ-aminobutyric acid (GABA) as spacers. After spacer N-formylation, followed by dehydration, isocyanide functionalised resins were obtained. The resins were then used in solid phase Ugi reaction, using phenylacetic acid as the acid component, 4-methoxybenzylamine as the amine component and different ketones, to afford the desired N-acylated α,α-dialkylglycines in good overall yields (60–80%), after acidolytic cleavage from the resin, thus proving the feasibility of this approach. 相似文献
994.
《合成通讯》2013,43(18):3233-3241
Abstract A concise synthesis of (2E,4Z)-2,4-heptadien-1-ol and (2E,4Z)-2,4-heptadienal is presented. Commercially available (Z)-2-penten-1-ol was converted to ethyl-(2E,4Z)-2,4-heptadienoate by reaction with activated MnO2 and (carboethoxymethylene)triphenylphosphorane in the presence of benzoic acid as a catalyst. Ethyl-(2E,4Z)-2,4-heptadienoate was converted to (2E,4Z)-2,4-heptadien-1-ol with LiAlH4. The alcohol was partially oxidized to (2E,4Z)-2,4-heptadienal with MnO2. The title compounds are male-specific, antennally active volatile compounds from the Saltcedar leaf beetle, Diorhabda elongata Brulle (Coleoptera: Chrysomelidae) and have potential use in the biological control of the invasive weed saltcedar (Tamarix spp). 相似文献
995.
D.M. Fernandes J.L. Andrade M.K. Lima M.F. Silva L.H.C. Andrade S.M. Lima A.A. Winkler Hechenleitner E.A. Gómez Pineda 《Polymer Degradation and Stability》2013
Ni0.04Zn0.96O and Fe0.03Zn0.97O with average diameter of 23 and 19 nm, respectively, have been synthesized by a modified sol–gel method to be used in the preparation of (100 − x)/x poly(vinyl alcohol)/oxide nanocomposite films, with x = 0, 1, 3 and 5 (in wt.%). A 125 W-Hg vapor lamp with emission above 254 nmwas used to irradiate PVA/Ni0.04Zn0.96O and PVA/Fe0.03Zn0.97O films. The effect on their structural, thermal, morphological and optical properties was studied by TG, DSC, DRX, AFM, UV–vis and PL spectrophotometry. The Ni0.04Zn0.96O addition on PVA films decreases the thermal stability of the polymer in inert and in oxidative atmosphere. In contrast, the Fe0.03Zn0.97O presence in the PVA films seems to increase the thermal stability of the polymer. The characteristic peak of the crystalline phase of PVA and wurtzite phase of the zinc oxide were identified through X-ray diffraction in both films. The crystallinity of the PVA film increases with UV irradiation and with the presence of Ni0.04Zn0.96O and Fe0.03Zn0.97O. The roughness of the PVA film was not modified by the addition of the doped oxides; however, it increases after UV irradiation, more significantly in the films containing the oxides. The PVA film exhibits absorption around 280 nm characteristic of π–π∗ transitions related to carbonyl groups from residuals acetate, while the 95/05 PVA/Ni0.04Zn0.96O and 95/05 PVA/Fe0.03Zn0.97O nanocomposite films show absorption at the visible region which is characteristics of the band gap reduction of the doped oxides. The photoluminescence of PVA was modified by the presence of the oxides in the film. These nanocomposite films are interesting due to their thermal, mechanical (flexible) properties and low cost of production. In addition they are also able to exhibit peculiar optical properties showing potential to be used in photonic devices, gas sensors and organic solar cell applications. 相似文献
996.
Pierre-Olivier Bussière Jérémy Peyroux Geneviève Chadeyron Sandrine Therias 《Polymer Degradation and Stability》2013
The photochemical behaviour of polymer–nanoparticles/nanocomposites has been studied depending on the geometry of the nanofiller and an overview of the studies reported in the last decade is tentatively given. Depending on their functionality, nanoparticles can impact the durability of the nanocomposite materials under light irradiation. The behaviour to UV-light exposure in presence of oxygen of various types of nanocomposites with clays, LDH and carbon nanotubes has been investigated and recent progress on the influence of functional nanoparticles on the polymer photodegradation is reported. The influence of photocatalytic (ZnO and TiO2) nanoparticles and phosphors on the photooxidation of the polymeric matrix and the durability of the material properties are characterized. From a general point of view, the stabilization strategy of polymer nanocomposites must be adapted depending on the nanofiller. 相似文献
997.
Qiufen Wang Ying Huang Yang Zhao Wei Zhang Yan Wang 《Surface and interface analysis : SIA》2013,45(8):1297-1303
Tin‐based oxide Li2SnO3 has been synthesized by a hydrothermal route as negative material for lithium‐ion batteries. The microstructure and electrochemical properties of the as‐synthesized materials were investigated by some characterizations means and electrochemical measurements. The as‐synthesized Li2SnO3 is a porous rod, which is composed of many uniform and regular nano‐flakes with a size of 50–60 nm. Li2SnO3 also displays an electrochemical performance with high capacity and good cycling stability (510.2 mAh g?1 after 50 cycles at a current density of 60 mA g?1 between 0.0 V and 2.0 V verusus Li/Li+). Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
998.
Silver nanolayers sputtered on polytetrafluoroethylene and their changes induced by post‐deposition annealing at 100–300 °C are studied. Changes in surface morphology and roughness are examined by atomic force microscopy and by measurement of electrical sheet resistance by two‐point technique. Chemical composition was determined by X‐ray photoelectron spectroscopy (XPS) and electrokinetic analysis in dependence on the gold layer thickness. The annealing at 300 °C leads to significant rearrangement of the silver layer, and the transition threshold increases to 35 nm. The presence of oxidized structures on silver‐coated samples is observed in XPS spectra and by electrokinetic analysis, too. Annealing of pristine and silver‐coated poly(tetrafluoroethylene) at 300 °C results in significant change of the sample surface morphology and chemistry. There is observed formation of isolated silver islands on the surface, which could be connected with silver melting. Later, the silver agglomeration takes place. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
999.
Phase change material (PCM, octadecane) nanocapsules were successfully prepared by resin fortified emulsion (RFE) polymerization using the alkali soluble resin (ASR) of poly(ethylene‐co‐acrylic acid) (EAA) and poly(styrene‐co‐acrylic acid) (SAA). Stable PCM nanocapsules were obtained by resin fortified emulsion polymerization, which could be attributed to the prevention of Ostwald ripening due to PCM being hydrophobic. Analysis of online FTIR measurements throughout the reaction confirmed that the nanocapsules contained octadecane as a PCM. TEM imaging of the PCM nanocapsules showed spherical and core/shell morphology. The characteristics of PCM nanocapsules can be controlled by process parameters. As a result, the particle size and particle size distribution (i.e., polydispersity index (Dw/Dn)) of the PCM nanocapsules were created by adjusting manufacturing conditions. The PCM nanocapsules exhibited thermal energy storage (~49.8 J/g) and release (~47.9 J/g) behavior. 相似文献
1000.