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61.
Belal TS 《Journal of fluorescence》2008,18(5):771-780
A simple, rapid, selective and sensitive spectrofluorimetric method was described for the analysis of three nitrofuran drugs,
namely, nifuroxazide (NX), nitrofurantoin (NT) and nitrofurazone (NZ). The method involved the alkaline hydrolysis of the
studied drugs by warming with 0.1 M sodium hydroxide solution then dilution with distilled water for NX or 2-propanol for
NT and NZ. The formed fluorophores were measured at 465 nm (λ
Ex 265 nm), 458 nm (λ
Ex 245 nm) and 445 nm (λ
Ex 245 nm) for NX, NT and NZ, respectively. The reaction pathway was discussed and the structures of the fluorescent products
were proposed. The different experimental parameters were studied and optimized. Regression analysis showed good correlation
between fluorescence intensity and concentration over the ranges 0.08–1.00, 0.02–0.24 and 0.004–0.050 μg ml−1 for NX, NT and NZ, respectively. The limits of detection of the method were 8.0, 1.9 and 0.3 ng ml−1 for NX, NT and NZ, respectively. The proposed method was validated in terms of accuracy, precision and specificity, and it
was successfully applied for the assay of the three nitrofurans in their different dosage forms. No interference was observed
from common pharmaceutical adjuvants. The results were favorably compared with those obtained by reference spectrophotometric
methods. 相似文献
62.
Abdollah Salimi Mohadeseh Izadi Rahman Hallaj Saied Soltanian Hassan Hadadzadeh 《Journal of Solid State Electrochemistry》2009,13(3):485-496
A simple procedure was developed to prepare a glassy carbon electrode modified with carbon nanotubes and Ruthenium (III) complexes.
First, 25 μl of dimethyl sulfoxide–carbon nanotubes solutions (0.4 mg/ml) was cast on the surface of the glassy carbon electrode
and dried in air to form a carbon nanotube film at the electrode surface. Then, the glassy carbon/carbon nanotube-modified
electrode was immersed into a Ruthenium (III) complex solution (direct deposition) for a short period of time (10–20 s for
multiwalled carbon nanotubes and 20–40 s for single-walled carbon nanotubes). The cyclic voltammograms of the modified electrode
in aqueous solution shows a pair of well-defined, stable, and nearly reversible redox couple, Ru(III)/Ru(II), with surface-confined
characteristics. The attractive mechanical and electrical characteristics of carbon nanostructures and unique properties and
reactivity of Ru complexes are combined. The transfer coefficient (α), heterogeneous electron transfer rate constants (k
s), and surface concentrations (Γ) for the glassy carbon/single-walled carbon nanotubes/Ru(III) complex-, glassy carbon/multiwalled carbon nanotubes/Ru(III)
complex-, and glassy carbon/Ru(III) complex-modified electrodes were calculated using the cyclic voltammetry technique. The
modified electrodes showed excellent catalytic activity, fast response time, and high sensitivity toward the reduction of
nicotinamide adenine dinucleotide in phosphate buffer solutions at a pH range of 4–8. The catalytic cathodic current depends
on the nicotinamide adenine dinucleotide concentration. In the presence of alcohol dehydrogenase, the modified electrode exhibited
a response to addition of acetaldehyde. Therefore, the main product of nicotinamide adenine dinucleotide electroreduction
at the Ru(III) complex/carbon nanotube-modified electrode was the enzymatically active NADH. The purposed sensor can be used
for acetaldehyde determination. 相似文献
63.
64.
Saied Saeed Hosseiny Davarani Amin Morteza NajarianSaeed Nojavan Mohammad-Ali Tabatabaei 《Analytica chimica acta》2012
Recent advances in electromembrane extraction (EME) methodology calls for effective and accessible detection methods. Using imipramine and clomipramine as model therapeutics, this proof-of-principle work combines EME with gas chromatography analysis employing a flame ionization detector (FID). The drugs were extracted from acidic aqueous sample solutions, through a supported liquid membrane (SLM) consisting of 2-nitrophenyl octyl ether (NPOE) impregnated on the walls of the hollow fiber. EME parameters, such as SLM composition, type of ion carrier, pH and the composition of donor and acceptor solutions, agitation speed, extraction voltage, and extraction time were studied in detail. Under optimized conditions, the therapeutics were effectively extracted from different matrices with recoveries ranging from 90 to 95%. The samples were preconcentrated 270–280 times prior to GC analysis. Reliable linearity was also achieved for calibration curves with a regression coefficient of at least 0.995. Detection limits and intra-day precision (n = 3) were less than 0.7 ng mL−1 and 8.5%, respectively. Finally, method was applied to determination and quantification of drugs in human plasma and urine samples and satisfactory results were achieved. 相似文献
65.
Saied Saeed HosseinyDavarani Hamid Reza Moazami Elham Memarian Saeed Nojavan 《Electrophoresis》2016,37(2):339-346
Electromembrane extraction (EME) of model analytes was carried out using a virtually rotating supported liquid membrane (SLM). The virtual (nonmechanical) rotating of the SLM was achieved using a novel electrode assembly including a central electrode immersed inside the lumen of the SLM and five counter electrodes surrounding the SLM. A particular electronic circuit was designed to distribute the potential among five counter electrodes in a rotating pattern. The effect of the experimental parameters on the recovery of the extraction was investigated for verapamil (VPL), trimipramine (TRP), and clomipramine (CLP) as the model analytes and 2‐ethyl hexanol as the SLM solvent. The results showed that the recovery of the extraction is a function of the angular velocity of the virtual rotation. The best results were obtained at an angular velocity of 1.83 RadS?1 (or a rotation frequency of 0.29 Hz).The optimization of the parameters gave higher recoveries up to 50% greater than those of a conventional EME method. The rotating also allowed the extraction to be carried out at shorter time (15 min) and lower voltage (200 V) with respect to the conventional extraction. The model analytes were successfully extracted from wastewater and human urine samples with recoveries ranging from 38 to 85%. The RSD of the determinations was in the range of 12.6 to 14.8%. 相似文献
66.
Seyed Farhad Hosseini Ali Hashemian Behnam Moetakef-Imani Saied Hadidimoud 《Acta Mechanica Sinica》2018,34(4):728-743
In the present paper, the isogeometric analysis (IGA) of free-form planar curved beams is formulated based on the nonlinear Timoshenko beam theory to investigate the large deformation of beams with variable curvature. Based on the isoparametric concept, the shape functions of the field variables (displacement and rotation) in a finite element analysis are considered to be the same as the non-uniform rational basis spline (NURBS) basis functions defining the geometry. The validity of the presented formulation is tested in five case studies covering a wide range of engineering curved structures including from straight and constant curvature to variable curvature beams. The nonlinear deformation results obtained by the presented method are compared to well-established benchmark examples and also compared to the results of linear and nonlinear finite element analyses. As the nonlinear load-deflection behavior of Timoshenko beams is the main topic of this article, the results strongly show the applicability of the IGA method to the large deformation analysis of free-form curved beams. Finally, it is interesting to notice that, until very recently, the large deformations analysis of free-form Timoshenko curved beams has not been considered in IGA by researchers. 相似文献
67.
We describe a novel method for the synthesis a new magnetic bromochromate hybrid nanomaterial, Fe3O4@SiO2@TEA@[CrO3Br], as a catalyst. The physical properties, morphology and magnetic investigations of magnetic bromochromate hybrid nanomaterials are identified by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) techniques. Fourier transform infrared (FT-IR), elemental analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD) were also used for structural identification. The quantity of chromium is approximately 0.38%, which confirms to the immobilization amount of [CrO3Br]- and is equal to 0.007 mol/100 g. 相似文献
68.
Ghassempour A Najafi NM Mehdinia A Davarani SS Fallahi M Nakhshab M 《Journal of chromatography. A》2005,1078(1-2):120-127
A simple and sensitive method for determining anatoxin-a in aqueous samples was developed using solid-phase microextraction (SPME) and gas chromatography with mass spectrometry (GC-MS) detection. Three forms of polyaniline (PANI) films and a single form of polypyrrole (PPY) film were prepared and applied for SPME. The extraction properties of these films to anatoxin-a were examined and it was shown that leucoemeraldine form of PANI displayed a better selectivity to this compound. SPME conditions were optimized by selecting the appropriate extraction parameters, including type of coating (leucoemeraldine form of PANI at 32 microm thicknesses), salt concentration (10%, w/v), time of extraction (30 min) and stirring rate (1000 rpm). The calibration curve was linear in the range from 50 to 10,000 ng/ml, with the detection limit (S/N = 3) of 11.2 ng/ml. This method was successfully applied for the analysis of anatoxin-a in the cultured media of two species of cyanobacteria. 相似文献
69.
The Atomic Energy Commission of Syria (AECS), in cooperation with the Arabic Atomic Energy Agency (AAEA), has initiated the
first proficiency test exercise for the determination of naturally occurring radioactive materials (NORM) in contaminated
soil from the oil field. The soil sample was collected from one of the most highly radioactively contaminated lagoons with
production water in the Syrian oil fields, which was then prepared, characterised and certified according to a standard procedure.
Samples were dispatched to laboratories from eight Arab countries; Kuwait, Egypt, Yemen, Tunisia, Jordan, the Kingdom of Saudi
Arabia, Libya and Syria. The results were evaluated using three statistical criteria; z-score, the U
test score and the relative bias. These statistical methods were used to evaluate the performance of each laboratory, in addition
to the overall evaluation for each radionuclide. This evaluation has indicated that 57% and 86% of the results passed the
criteria set for precision and accuracy applied for this test in relation to 226Ra and 228Ra, respectively. These two radionuclides are considered to be the most important radionuclides in the oil industry. 相似文献
70.