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1.
Polarographic determination of uranium (VI) has been studied in the organic extraction phase TBP—diluent along with a selected
aprotic solvent (i. e. dimethyl sulfoxide or N,N-dimethylformamide). DMF was found more suitable because it dissolves the
organic extraction phase better than DMSO. U (VI) extracted in TBP-kerosene, n-hexane, cyclohexane, n-dodecane, benzene, from
nitric acid medium can be determined in an organic solution (e. g. 50% DMF-30% TBP-20% kerosene) where it gives a well defined
wave. In the organic solution, nitric acid added and/or extracted from the aqueous phase was found as an excellent supporting
electrolyte for uranium determination. 相似文献
2.
Summary The influence of the isothermal temperature, program rate, initial temperature and flow rate on retention indices was studied. The methods of Kováts, Van Den Dool and Local Lagrange Interpolation are compared. Ten experimental measurements were carried out on a capillary column coated with OV-101 stationary phase. 相似文献
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Fayçal Boukhari Nacéra Tigrine‐Kordjani Brahim Youcef Meklati 《Helvetica chimica acta》2013,96(6):1168-1175
Walnut (Juglans regia L.) leaves are used traditionally as an herbal tea indicated for non‐insulin‐dependent diabetics. In recent years, the type‐II diabetes is occurring worldwide with increasing frequency. Thus, there is an urgent need to explore the new beneficial biomolecules on the human health. Our objective was to investigate, for the first time, the volatiles profile of Juglans regia L. leaves from Algiers region. The extraction of essential oil of fresh plant material was performed by microwave‐assisted hydrodistillation (MAHD), for the first time, a relatively recent method, then by the conventional hydrodistillation technique (HD) for comparison. The collected extracts were analyzed by GC‐FID and GC/MS using two capillary columns with different polarity. Extraction time of 1 h by MAHD provided higher yields (0.050±0.001% (w/w)) than by HD (0.030±0.006% (w/w)) after 3 h. A total of 38 compounds were identified using both techniques. Essential oils had similar qualitative but different quantitative composition in terms of chemical compounds. The MAHD method improved yield while reducing the extraction time. The sesquiterpenes were the dominant family in both MAHD and HD essential oils with β‐caryophyllene being the major constituent. Monoterpenes, including hydrocarbon and oxygenated, prevail in HD volatile fraction with β‐pinene and eucalyptol, respectively, as major components. 相似文献
4.
Mohamed El MESSOUDI Aicha BOUKHRISS Laila SADALLAH Laila SAJID M'hamed El KOUALI Said GMOUH 《高等学校化学研究》2020,36(5):877-884
In this paper, phosphate nanoparticles were coated on cotton(CO) and polyester(PES) textile surfaces by sol-gel method using tetraethylorthosilicate(TEOS) and chloropropyltriethoxysilane(CPTS) as silica precursors. The deposited nanoparticles were observed with scanning electronic microscopy energy-dispersive X-ray spectroscopy (SEM-EDX). The release kinetics of phosphorus(P) from these textiles into the aqueous medium(Aq), acid(Ac), and basic(Ba) artificial sweats were then studied. The released amount of phosphorus was evaluated by the inductively coupled plasma(ICP) according to ISO NF EN 16711-2 procedure. The results revealed that the release of P into the aqueous medium is lower than in the artificial sweat. The kinetics data[the phosphorus desorption amount(mg/g) as a function of time] were modeled according to five models:the first order, the second order, the third order, simple Elovich and parabolic diffusion. The suitable model was chosen based on the coefficient of determination(R2) and the calculation of the sum of the absolute errors(EABS), which describes the error between the theoretical and experimental values. SEM observations were also carried out on the fabrics after desorption in order to show the impact of desorption on their morphology. Furthermore, the impact of P release on the tensile strength of CO and PES fabrics was investigated using a uniaxial tensile test. The thermal stability of all samples before and after desorption was assessed by thermogravimetric analysis(ATG). 相似文献
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Preparation and coordination complex of the first imine-bridged tetrathiafulvalene-pyridine donor ligand 总被引:1,自引:0,他引:1
Chahma M Hassan N Alberola A Stoeckli-Evans H Pilkington M 《Inorganic chemistry》2007,46(10):3807-3809
The first imine-bridged pyridyltetrathiafulvalene building block (TTF-CH=N-Py, 1) has been synthesized via the Schiff base condensation of formyltetrathiafulvalene and 2-aminopyridine. The preparation, X-ray crystal structure, electrochemical and magnetic characterization of a 1:1 copper complex [CuII(hfac)2(TTF-CH=N-Py)] (2) are reported. The crystal structure reveals that the imine N atom participates in chelation to the paramagnetic center, thus making this ligand an attractive precursor for the assembly of pi-d systems. 相似文献
7.
Linda Didaoui A. Touabet A. Y. Badjah Hadj Ahmed B. Y. Meklati Werner Engewald 《Journal of separation science》1999,22(10):559-564
In reversed phase liquid chromatography (RP-HPLC), the validity of a multiparametric non-linear least-squares regression iterative method for the determination of the column dead time tM and the regression parameter (slope b), based on the use of alkan-2-ones, alkyl aryl ketones, and 1-nitroalkanes has been evaluated. The determination of tM and b has been extensively studied for two mobile phase systems acetonitrile-water and methanol-water on seven octadecyl-C18 and one octyl C8 analytical columns. The calculated tM and b values were compared with those obtained by Guardino's and Grobler's methods. The influence exerted thereon by the nature of the homologous series, the mobile phase composition, and the packing materials were investigated. 相似文献
8.
Dr. Xin Chen Malte Kohring Dr. M'hamed Assebban Dr. Bartłomiej Tywoniuk Dr. Cian Bartlam Narine Moses Badlyan Prof. Janina Maultzsch Prof. Georg S. Duesberg Prof. Heiko B. Weber Dr. Kathrin C. Knirsch Prof. Andreas Hirsch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13117-13122
The development of an efficient method to patterning 2D MoS2 into a desired topographic structure is of particular importance to bridge the way towards the ultimate device. Herein, we demonstrate a patterning strategy by combining the electron beam lithography with the surface covalent functionalization. This strategy allows us to generate delicate MoS2 ribbon patterns with a minimum feature size of 2 μm in a high throughput rate. The patterned monolayer MoS2 domain consists of a spatially well-defined heterophase homojunction and alternately distributed surface characteristics, which holds great interest for further exploration of MoS2 based devices. 相似文献
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Chahma M Li X Phillips JP Schwartz P Brammer LE Wang Y Tanko JM 《The journal of physical chemistry. A》2005,109(15):3372-3382
By using direct and indirect electrochemical methods, rate constants (ko) for cyclopropane ring opening of radical anions derived from the one-electron reduction of trans-1-benzoyl-2-phenylcyclopropane, trans-1-benzoyl-2-vinylcyclopropane, 2-methylenecyclopropyl phenyl ketone, spiro[anthracene-9,1'-cyclopropan-10-one], 3-cyclopropylcyclohex-2-en-1-one, and 3-(1-methylcyclopropyl)cyclohex-2-en-1-one were determined. Qualitatively, rate constants for ring opening of these (and other cyclopropyl- and cyclobutyl-containing radical anions) can be rationalized on the basis of the thermodynamic stability of the radical anion, the ability of substituents on the cyclopropyl group to stabilize the radical portion of the distonic radical anion, and the stability of the enolate portion of the distonic radical anion. On the basis of this notion, a thermochemical cycle for estimating deltaG(o) for ring opening was presented. For simple cyclopropyl-containing ketyl anions, a reasonable correlation between log(ko) and deltaG(o) was found, and stepwise dissociative electron transfer theory was applied to rationalize the results. Activation energies calculated with density functional theory (UB3LYP/6-31+G*) correlate reasonably well with measured log(ko). The derived log(ko) and deltaG(o) and log(ko) vs E(a) plots provide the basis for a "calibration curve" to predict rate constants for ring opening of radical anions derived from carbonyl compounds, in general. 相似文献