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排序方式: 共有640条查询结果,搜索用时 31 毫秒
621.
Karimi B Behzadnia H Rafiee M Vali H 《Chemical communications (Cambridge, England)》2012,48(22):2776-2778
A novel nano-fibrillated mesoporous carbon (IFMC) was found to be an effective modifier in combination with ionic liquid 1-octylpyridinum hexafluorophosphate (OPFP) as a binder to give impregnated graphite electrodes with outstanding electrochemical performances. 相似文献
622.
623.
Mohammad Ali Karimi Abdolhamid Hatefi-Mehrjardi Sayed Zia Mohammadi Alireza Mohadesi Mohammad Mazloum-Ardakani Mohammad Reza Hormozi Nezhad Asghar Askarpour Kabir 《Journal of the Iranian Chemical Society》2012,9(2):171-180
A new, simple, fast and reliable solid-phase extraction method has been developed for separation/preconcentration of trace amounts of Pb(II) using dithizone/sodium dodecyl sulfate-immobilized on alumina-coated magnetite nanoparticles, and its determination by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) after eluting with 4.0?mol?L?1 HNO3. Optimal experimental conditions including pH, sample volume, eluent concentration and volume, and co-existing ions have been studied and established. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation of Pb(II) using FAAS technique were 280 (for 560?mL of sample solution), 0.28?ng?mL?1, 1.4?C70?ng?mL?1 and 4.6% (for 10?ng?mL?1, n?=?10), respectively. These analytical parameters using GFAAS technique were 300 (for 600?mL of sample solution), 0.002?ng?mL?1, 0.006?C13.2?ng?mL?1 and 3.1% (for 5?ng?mL?1, n?=?10), respectively. The presented procedure was successfully applied for determination of Pb(II) content in opium, heroin, lipstick, plants and water samples. 相似文献
624.
625.
New highly organosoluble metallophthalocyanines (M = Zn, Co, Ni and Cu) bearing four [4-(3,3,6,6-tetramethyl-1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)phenoxy] substituents at peripheral positions have been prepared by tetramerization of 4-[4-(3,3,6,6-tetramethyl-1,8-dioxo-dodecahydro-1H-xanthen-9-yl)phenoxy]phthalonitrile in 2-(dimethylamino)ethanol using microwave irradiation or conventional heating. Ni(II), Co(II), and Cu(I) chloride were employed in order to synthesize the corresponding metal phthalocyanines and Zn(OAc)2 was used for the preparation of the zinc phthalocyanines. 4-[4-(3,3,6,6-Tetramethyl-1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)phenoxy]phthalonitrile was obtained by nucleophilic displacement of the nitro group in 4-nitrophthalonitrile with 9-(4-hydroxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione. 9-(4-Hydroxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione was synthesized efficiently from dimedone and 4-hydroxybenzaldehyde. All the phthalocyanines are soluble in DMSO, DMF, CHCl3, THF, CH2Cl2, and CH3CN. The new compounds were characterized by IR, NMR, and UV–vis spectroscopy, elemental analysis, and thermogravimetric analysis. 相似文献
626.
Fabrication and application of a voltammetric sensor based on gold 2-mercaptobenzothiazole self-assembled monolayer (Au-MBT SAM) for determination of silver ion is described. Preliminary experiments were performed to characterize the monolayer. The surface pKa determined for the MBT monolayer is 7.0. This value was obtained by impedimetric titration of the monolayer in the presence of Fe(CN)63−/4− as a redox probe. The extent of surface coverage was evaluated as 1.52 × 10−9 mol cm−2 based on charged consumed for reductive desorption of the monolayer in the 0.50 M NaOH solution. Then the sensor was used for determination of Ag(I) by square wave voltammetry. The parameters affecting the sensor response, such as pH and supporting electrolyte, were optimized. A dynamic calibration curve with two linear parts was obtained in the concentration ranges of 5 × 10−8-8 × 10−7 and 1 × 10−6-1 × 10−5 M of Ag(I). The detection limit adopted from cathodic striping square wave voltammetry was as 1 × 10−8 M for n = 7. Furthermore, the effect of potential interfering ions on the determination of Ag(I) was studied, and an appropriate method was used for the elimination of this effect. 相似文献
627.
Shervedani RK Mehrjardi AH Zamiri N 《Bioelectrochemistry (Amsterdam, Netherlands)》2006,69(2):201-208
A method is developed for quantitative determination of glucose using electrochemical impedance spectroscopy (EIS). The method is based on immobilized glucose oxidase (GOx) on the topside of gold mercaptopropionic acid self-assembled monolayers (Au-MPA-GOx SAMs) electrode and mediation of electron transfer by parabenzoquinone (PBQ). The PBQ is reduced to hydroquinone (H(2)Q), which in turn is oxidized at Au electrode in diffusion layer. An increase in the glucose concentration results in an increase in the diffusion current density of the H(2)Q oxidation, which corresponds to a decrease in the faradaic charge transfer resistance (R(ct)) obtained from the EIS measurements. Glucose is quantified from linear variation of the sensor response (1/R(ct)) as a function of glucose concentration in solution. The method is straightforward and nondestructive. The dynamic range for determination of glucose is extended to more than two orders of magnitude. A detection limit of 15.6 microM with a sensitivity of 9.66 x 10(-7) Omega(-1)mM(-1) is obtained. 相似文献
628.
A modified principle component artificial neural network (PC-ANN) model is developed for simultaneous determination of thiocyanate and salycilate concentration after passing through the bulk of a liquid membrane by tri-phenyl benzyl phosphonium chloride. All calibration, and test samples data were obtained using UV-Vis spectrophotometer. In this way, a modified PC-ANN consisting of three layers of nodes was trained by combination of Bayesian-Levenberg-Marquardt as training rule. Sigmoid and liner transfer functions were used in the hidden and output layers respectively to facilitate nonlinear calibration. The model could accurately estimate the concentration of components with acceptable precision and accuracy, for mixtures. The PC-ANN model exhibits a good ability for the simultaneous determination of the thiocyanate and salycilate in concentration range 0.5 x 10(-4) mol.l(-1) up to 5.0 x 10(-4) mol.l(-1) with Root Mean square error (2.22% and 2.20%, for thiocyanate and salycilate, respectively) and high correlation coefficients (R2= 0.998 or greater). Results obtained with modified trained PC-ANN were compared with stepwise linear regression (SMLR) model. Validation of the two models shows a better ability in estimation of the modified PC-ANN as compared with the SMLR model (MSRE given are 3.12%, 6.31%.). 相似文献
629.
Javad Azizian Farhad Hatamjafari Ali Reza Karimi 《Journal of heterocyclic chemistry》2006,43(5):1349-1352
630.
Javad Azizian Ali A. Mohammadi Ebrahim Soleimani Ali R. Karimi Mohammad R. Mohammadizadeh 《Journal of heterocyclic chemistry》2006,43(1):187-190