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排序方式: 共有1413条查询结果,搜索用时 328 毫秒
21.
Jibrin Sabo Suleiman Bin Hu Xuli Pu Chaozhang Huang Zucheng Jiang 《Mikrochimica acta》2007,159(3-4):379-385
A new method is proposed using a microcolumn (20 mm × 2.0 mm) packed with nanometer-sized zirconia as solid-phase extractor
for the separation/preconcentration of Mn, Cu, Cr, Zn, Ni and Co prior to their determination by inductively coupled plasma
optical emission spectrometer (ICP-OES) in environmental samples. The factors affecting the separation and preconcentration
of analytes such as pH, sample flow rate and volume, eluent concentration and volume were determined, interfering ions were
studied, and the optimal experimental conditions were established. The adsorption capacity of nanometer-sized ZrO2 for Mn, Cu, Cr, Zn, Ni and Co was found to be 1.3, 1.3, 1.7, 2.0, 3.9 and 1.5 mg g−1, respectively. The detection limits of the method were 12, 58, 24, 2, 7 and 36 ng L−1, respectively, with a preconcentration factor of 25. The precision of this method was 1.7% (Mn), 2.9% (Cu), 5.9% (Mn), 3.8%
(Mn), 6.2% (Mn) and 4.3% (Mn) with 9 determinations of 10 ng mL−1 of target analytes, respectively. The method was successfully applied to the determination of trace metals in lake water,
dried fish samples, certified reference materials of human hair and milk, and provided satisfactory results. 相似文献
22.
The effects of intermolecular interactions on the second-order susceptibilities ((2)) of molecular crystals are studied by using a semiempirical quantum–chemical method. These effects are discussed on the basis of the super-molecular approach. The influence of the electrostatic interactions between adjacent unit cells on the tensor components of (2) was modeled by using the technique of cumulative atomic multipole moments (CAMMs). 相似文献
23.
Puoci F Iemma F Muzzalupo R Spizzirri UG Trombino S Cassano R Picci N 《Macromolecular bioscience》2004,4(1):22-26
Spherical molecularly imprinted polymers (SMIPs) have been prepared via a novel precipitation polymerization using sulfasalazine (prodrug used in the diseases of the colon) as template. The sulfasalazine was incorporated into SMIPs and into a spherical non-imprinted polymer (control), and then the release rate of the bioactive agent at different pH values was evaluated. Considerable differences in the release characteristics between imprinted and non-imprinted polymers have been observed. This opens the possibility of the development of drug release systems capable of modulating the release of a specific molecule. Photomicrography of spherical molecularly imprinted polymers (SMIPs). 相似文献
24.
A new high-performance liquid chromatographic/electrospray ionization tandem mass spectrometric (HPLC/ESI-MS/MS) method was developed for the simultaneous quantification of 5-fluorouracil (5FU), methotrexate (MTX) and cyclophosphamide (CP) in environmental samples. These compounds, commonly used in the treatment of cancer, are recognized as genotoxic. In order to estimate the occupational exposure of hospital personnel handling these drugs, wipe samples were taken from the working surfaces and directly analyzed (with trophosphamide as internal standard) using a reversed-phase capillary column and MS/MS detection. This is the first HPLC/MS/MS method for the simultaneous determination of 5FU, MTX and CP. The present method offers high sensitivity, with detection limits of 1.1 microg l(-1) for MTX and CP and 33.3 microg l(-1) for 5FU, avoiding any sample preconcentration procedure. Rapidity, specificity, high accuracy (mean values between 92.4 and 99.9%) and precision (mean RSD values between 3.4 and 12.1%) make the method suitable for the routine determination of these three antineoplastic drugs. 相似文献
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27.
Dr. Mahnaz Najafi Dr. Sara Abednatanzi Abbas Yousefi Prof. Mehrorang Ghaedi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(72):17999-18014
Photocatalysis has been known as one of the promising technologies due to its eco-friendly nature. However, the potential application of many photocatalysts is limited owing to their large bandgaps and inefficient use of the solar spectrum. One strategy to overcome this problem is to combine the advantages of heteroatom-containing supports with active metal centers to accurately adjust the structural parameters. Metal nanoparticles (MNPs) and single atom catalysts (SACs) are excellent candidates due to their distinctive coordination environment which enhances photocatalytic activity. Metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and carbon nitride (g-C3N4) have shown great potential as catalyst support for SACs and MNPs. The numerous combinations of organic linkers with various heteroatoms and metal ions provide unique structural characteristics to achieve advanced materials. This review describes the recent advancement of the modified MOFs, COFs and g-C3N4 with SACs and NPs for enhanced photocatalytic applications with emphasis on environmental remediation. 相似文献
28.
F. Deyhimi F. Mermoud F. O. Gülaçlar A. Buchs 《International journal of environmental analytical chemistry》2013,93(1-2):75-85
Abstract The use of classical urea inclusion techniques for the separation of straight chain hydrocarbons from branched and cyclic compounds is satisfactory when applied to mixtures in the milligram to gram ranges, but leads to low separation efficiencies when quantities in the microgram to milligram range are involved. In this study, a modified inclusion technique using an urea-packed milli-bore column and a catalytic eluent is described. Examples of its use for the separation of mixtures of linear and cyclic hydrocarbons from 30μg up to a few milligrams are given. The versatility of this technique for the analyses of low amounts of environmental samples is described, and an application to the hydrocarbon fraction of surface sediment from lake Leman (Switzerland) is presented. 相似文献
29.
E. V. Pinneker B. I. Pisarski S. E. Pwalowa 《Isotopes in environmental and health studies》2013,49(3-4):313-320
Abstract The isotopic composition (D, 18O, 87Sr, 3He) of thermal and mineral waters of Mongolia is discussed. The Sr-isotope ratio depends on the rock's contact. Near the Chubsugul-lake 3He-/4He-values are high. A certain similarity between the waters of Mongolia and those of East Siberia can be derived from the obtained data. 相似文献
30.
J. M. Ferreira Liliana Caramelo R. P. Chhabra 《International Journal of Mathematical Education in Science & Technology》2013,44(4):545-552
A curve fitting model is presented which minimizes the sum of squares of relative residues and expressions for the fit coefficients and their respective errors are derived. The new model is compared to the normal least squares model, using as an example the Reynolds number-drag coefficient data for a sphere. The results show that the best fit was obtained with the new model, indicating it may provide a useful tool for data analysis. 相似文献