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排序方式: 共有340条查询结果,搜索用时 15 毫秒
91.
Hemmateenejad B Akhond M Miri R Shamsipur M 《Journal of chemical information and computer sciences》2003,43(4):1328-1334
92.
A new micelle-mediated extraction method for preconcentration of ultra-trace quantities of beryllium and aluminum as a prior step to their simultaneous spectrophotometric determination has been developed. Chrome Azurol S (CAS), cetyltrimethylammonium bromide (CTAB) and Triton X-114 were used as chelating agent, cationic surfactant for extraction and co-extraction agent, respectively. Mean centering (MC) of ratio spectra has been used for simultaneous analysis of beryllium and aluminum. The optimal extraction and reaction conditions were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 5-40 ng mL−1 of beryllium and 3-100 ng mL−1 of aluminum. The detection limit of the method is 0.98 and 0.52 ng mL−1 for beryllium and aluminum, respectively. The interference effect of some anions and cations was also tested. The method was applied to the simultaneous determination of beryllium in water samples. 相似文献
93.
Simultaneous determination of phenol and mononitrophenol isomers using PLS regression and conventional and derivative spectrophotometry 总被引:1,自引:0,他引:1
The partial least squares regression method (PLS) was tested as a calibration procedure for the simultaneous determination of phenol, o-nitrophenol, m-nitrophenol and p-nitrophenol by both conventional and first derivative UV/Vis spectrophotometry. The experiments were conducted in the acidic, neutral and basic media. The results obtained by the application of the PLS procedure on the conventional and first derivative spectra in two solvent media were compared. It was found that the results obtained in the basic medium have better performance characteristics than those obtained in the acidic or neutral media. Comparable results were obtained in the case of both conventional and first derivative absorbance data. The proposed method was applied to the determination of the four phenol derivatives in natural spiked water samples at concentration levels between 1.0 and 10.0 microg ml(-1) with average recoveries in the range 96% - 99%. 相似文献
94.
Forouzan Zonouzi Alireza Shayesteh Taher Alizadeh Hamid Dezhampanah Bahram Ghalami-Choobar Afsaneh Zonouzi 《中国化学会会志》2020,67(1):41-45
The (E)-2-hydroxy-5-(aryldiazenyl) benzaldehydes (azo dyes 1–4 ) were synthesized in high purity. As they are insoluble in water, the usual analytical methods cannot be utilized to determine their pKa values. Cyclic voltammetry was experimentally used to determine their pKa values in DMSO solvent. In addition, computational methods and a conductor-like screening model (COSMO) were used to calculate the solvent effect. , , Kexchange, and pKa values were estimated for the azo dyes being studied using the BP86, TPSS, B3LYP, PBE0, TPSSh, and PW6B95 density functionals in def2-TZVP basis sets. The obtained mean absolute deviations (MADs) indicate that the results of BP86, PBE0, and PW6B95 functionals are in good agreement with experimental values. 相似文献
95.
Valiollah Mirkhani Majid Moghadam Shahram Tangestaninejad Bahram Bahramian 《Monatshefte für Chemie / Chemical Monthly》2007,138(12):1303-1308
Summary. The Mn(III)-salen, containing phosphonium groups at the 5,5′-positions of the salen ligand supported on Amberlite IRA-200 via electrostatic binding was used for the oxidation of alkenes and alkanes with sodium periodate at room temperature in the
presence of imidazoles as axial ligands, and the effect of solvent, different axial ligands, and various oxygen donors was
investigated. This heterogenized catalyst shows high catalytic activity in alkene epoxidation and alkane hydroxylation. It
showed high selectivity in the epoxidation of stilbenes, α-pinene, and (R)-(+)-limonene, and exhibits a particular ability to epoxidize linear alkenes. The stability and reusability of this new heterogenized
metallo-salen complex was also investigated. The catalyst was characterized by FTIR, UV-Vis, SEM, and thermal analysis. 相似文献
96.
Bahram Mokhtari 《Supramolecular chemistry》2013,25(12):859-866
This paper introduces a supramolecular-based microextraction technique and examines its ability in preconcentration of tetrahedral oxoanions in the produced water. Diacid p-tert-butylcalix[4]arene in the cone conformation was synthesised and used. The respective parameters including ligand concentration, volume of aqueous disperser, salt effect and extraction time were optimised. The linear range, detection limit (S/N = 3) and precision (relative standard deviation, n = 6) were determined to be in the range of 1.0–280, 2.0–42.0 μg/l and 2.6–11.0%, respectively. 相似文献
97.
Bahram Sadeghi Bigham Marzieh Eskandari Maryam Tahmasbi 《Journal of computational science》2012,3(3):127-131
The polar diagram of a set of points in a plane and its extracted dual EDPD were recently introduced for static and dynamic cases. In this paper, the near-pole polar diagram NPPD for a set of points is presented. This new diagram can be considered as a generalization of the polar diagram and has applications in several communication systems and robotics problems. After reviewing the NPPD of points, we solve the problem for a set of line segments and simple polygons in optimal time Θ(n log n), where n is the number of line segments or polygon vertices. We introduce duality for the NPPD of points and identify some applications. 相似文献
98.
99.
Bahram Mashhoon 《General Relativity and Gravitation》1999,31(5):681-691
The inertial and gravitational properties ofintrinsic spin are discussed and some of the recent workin this area is briefly reviewed. The extension ofrelativistic wave equations to accelerated systems and gravitational fields is criticallyexamined. A nonlocal theory of accelerated observers ispresented and its predictions are compared withobservation. 相似文献
100.
Michael Hassul Bahram Shahian 《International Journal of Mathematical Education in Science & Technology》2013,44(6):915-918
A simplified method for the determination of inverse z‐transforms is presented. This technique provides an alternative to partial‐fraction expansion. With knowledge of the signal poles and the time domain sequence, the inverse z‐transform can be accomplished by solving a set of simultaneous equations. The time domain sequence is easily found by long division of the z‐transform. 相似文献