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排序方式: 共有269条查询结果,搜索用时 15 毫秒
91.
Ali Mehdinia Masoumeh Mashkani Ali Jabbari 《International journal of environmental analytical chemistry》2016,96(11):1091-1104
Extraction, pre-concentration and determination of trace amounts of mercury ions from water samples were investigated by magnetic solid phase extraction (MSPE) method using Fe3O4 nanoparticles decorated with polythionine as an adsorbent. A simple chemical synthesis by catalytic reaction of thionine in the presence of FeCl3 and hydrogen peroxide was used for preparation of the magnetic sorbent. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometer analysis and Fourier transform infrared spectroscopy were used to characterise the adsorbent. Mercury ions were determined by cold vapour atomic absorption spectrometry. The parameters for MSPE procedure, such as pH of the extraction solution, adsorption time, weight adsorbent, elution conditions (type, concentration and volume of the eluent), volume of the sample solution and effects of coexisting ions were investigated. The obtained optimal conditions were: sample pH of 4; sorbent amount of 4 mg; sorption time of 20 min; elution solvent of HNO3 (0.3 mol L?1)/thiourea (2% w/v) with volume of 2 mL, and breakthrough volume of 400 mL. A good linearity in the concentration range of 0.025–40 µg L?1 (R2 > 0.999) with the pre-concentration factor of 198 was obtained. The limits of detection and quantification were achieved as 0.008 and 0.025 µg L?1, respectively. Furthermore, sea and river water samples were analysed and good recoveries (97.1–99.6%) were obtained. 相似文献
92.
Masoumeh Mohammadnejad Mohsen Farhadpour Vahideh Mahdavi Mahmoud Tabrizchi 《International Journal for Ion Mobility Spectrometry》2017,20(1-2):23-30
Dichlorodiphenyl trichloroethane (DDT) as an organochlorine compound has been globally used as a pesticide for controlling soil-dwelling insects and treating diseases such as malaria and typhus. The degradation products of DDT and its metabolites have also negative effects on the environment. The present study has investigated the determination of DDT and its metabolites in water sample using ion mobility spectrometry (IMS) as a rapid and sensitive detection technique. For this purpose, DDT and its metabolites were extracted using reverse phase solid-phase extraction (SPE) from water samples. The samples were then recovered by eluting with methanol and finally, quantified using the corona discharge IMS technique. Injection and oven temperatures and the effect of dopant were optimized as experimental parameters influencing both detection and determination efficiencies. Degradation of DDT in IMS drift tube was studied and reduced mobility values of DDT and its metabolites were calculated. The developed method was validated using water sample to obtain good results for the determination of DDT at low levels (1 ng ml?1) while spiked recoveries were obtained to be between 95.0–96.7%. The proposed method based on IMS proved to be a simple, inexpensive, rapid and sensitive procedure for the fast monitoring and determination of DDT and its main metabolites in water sample. 相似文献
93.
A simple, low-cost, and effective cooling/heating-assisted headspace solid-phase microextraction (CHA–HS–SPME) device, capable of direct cooling the fiber to low temperatures and simultaneous heating the sample matrix to high temperatures, was fabricated and evaluated. It was able to cool down the commercial and handmade fibers for the effective tapping of volatile and semi-volatile species in the headspace of complex solid matrices, with minimal manipulation compared with conventional SPME. The CHA–HS–SPME system can create large temperature gaps (up to 200 °C) between the fiber and the sample matrix, because the cooling process is directly applied onto the fiber. 相似文献
94.
Ghalkhani M Fernandes IP Oliveira SC Shahrokhian S Oliveira-Brett AM 《Bioelectrochemistry (Amsterdam, Netherlands)》2011,80(2):175-181
Clioquinol is an antifungal, antiprotozoal and an Alzheimer's disease drug with cytotoxic activity toward human cancer cells. The electrochemical behavior of clioquinol and its oxidation product was studied using cyclic, differential pulse and square-wave voltammetry over a wide pH range on a glassy carbon electrode. The results revealed that the oxidation of clioquinol is an irreversible pH-dependent process that proceeds with the transfer of one electron and one proton in an adsorption-controlled mechanism and results in the formation of a main oxidation product, which adsorbs very strongly on the glassy carbon surface. The charge transfer coefficient was calculated as 0.64. The adsorbed oxidation product presented reversible redox behavior, with two electron and two proton transfer. The electrochemical oxidation of clioquinol as a phenolic compound involves the formation of a phenoxy radical which reacts in at least two ways: in one pathway the radical initiates polymerization, the products remaining at the electrode surface, and in the other the radical is oxidized to a quinone-like structure. A mechanism for the oxidation of clioquinol is proposed. 相似文献
95.
We consider the two-dimensional motion of the coupled system of a viscous incompressible fluid and a rigid disc moving with
the fluid, in the whole plane. The fluid motion is described by the Navier–Stokes equations and the motion of the rigid body
by conservation laws of linear and angular momentum. We show that, assuming that the rigid disc is not allowed to rotate,
as the radius of the disc goes to zero, the solution of this system converges, in an appropriate sense, to the solution of
the Navier–Stokes equations describing the motion of only fluid in the whole plane. We also prove that the trajectory of the
centre of the disc, at the zero limit of its radius, coincides with a fluid particle trajectory. 相似文献
96.
Masoumeh Zakeri Majid M. Heravi Mina Saeedi Narges Karimi Hossein A. Oskooie Niloofar Tavakoli‐Hoseini 《中国化学》2011,29(7):1441-1445
An efficient one‐pot condensation of β‐naphthol, aldehydes and cyclic 1,3‐dicarbonyl compound has been achieved with ionic liquids as catalyst, thus a variety of 8,9,10,12‐tetrahydrobenzo[a]xanthen‐11‐one derivatives were prepared in good yields. The present approach offers several advantages such as shorter reaction times, good yields and mild reaction conditions. 相似文献
97.
Mohammad T. Baei Ali Reza Soltani Ali Varasteh Moradi Masoumeh Moghimi 《Monatshefte für Chemie / Chemical Monthly》2011,21(6):573-578
Abstract
The behavior of N2O adsorbed on the external surface of H-capped (6,0), (7,0), (8,0), and Al-doped (6,0) zigzag single-walled carbon nanotubes was studied by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 03 suite of programs. We present the nature of the N2O interaction in selected sites of the nanotubes. Binding energies corresponding to adsorption of the N2O are calculated to be in the range 4–21 kJ mol−1. More efficient binding energies cannot be achieved by increasing the nanotube diameter. We also provide the effects of N2O adsorption on the electronic properties of the nanotubes. 相似文献98.
Poly(4-vinyl pyridine) supported nanoparticle of copper(Ⅰ) iodide is reported as a green and recyclable catalyst for the regioselective synthesis of 1,4-disubstituted-1H-1,2,3-triazoles from benzyl halides,sodium azide and terminal alkynes in water. This catalyst can be recovered by simple filtration and recycled up to 8 consecutive runs without any loss of its efficiency. 相似文献
99.
Tabatabaee M 《Chemistry Central journal》2012,6(1):5
Background
Various water clusters including hexamers, heptamers, octamers, decamers and 1D or 2D infinite water chains in a number of organic and inorganic-organic hybrid hosts, have been reported. 相似文献100.
In this paper, we investigate the existence of unique continuous linear extension for linear correspondences. We also give some results on cosine families of linear correspondences. 相似文献