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排序方式: 共有227条查询结果,搜索用时 109 毫秒
71.
Mohammad Bagher Gholivand Marzieh Piryaei Mir Mahdi Abolghasemi 《Journal of separation science》2013,36(5):872-877
Nanoporous silica was prepared and functionalized with amino propyl‐triethoxysilane to be used as a highly porous fiber‐coating material for solid‐phase microextraction (SPME). The prepared nanomaterials were immobilized onto a stainless steel wire for fabrication of the SPME fiber. The proposed fiber was evaluated for the extraction of volatile component of Citrus aurantium L. leaves. A homemade microwave‐assisted extraction followed by headspace (HS) solid‐phase apparatus was used for the extraction of volatile components. For optimization of factors affecting the extraction efficiency of the volatile compounds, a simplex optimization method was used. The repeatability for one fiber (n = 4), expressed as RSD, was between 3.1 and 8.6% and the reproducibility for five prepared fibers was between 10.1 and 14.9% for the test compounds. Using microwave‐assisted distillation HS‐SPME followed by GC‐MS, 53 compounds were separated and identified in C. aurantium L., which mainly included limonene (62.0%), linalool (7.47%), trans‐β‐Ocimene (3.47%), and caryophyllene (2.05%). In comparison to a hydrodistillation method, the proposed technique could equally monitor almost all the components of the sample, in an easier way, which was rapid and required a much lower amount of sample. 相似文献
72.
A cold column trapping-cloud point extraction (CCT-CPE) method coupled to high performance liquid chromatography (HPLC) was developed for preconcentration and determination of curcumin in human urine. A nonionic surfactant, Triton X-100, was used as the extraction medium. In the proposed method, a low surfactant concentration of 0.4% v/v and a short heating time of only 2 min at 70 °C were sufficient for quantitative extraction of the analyte. For the separation of the extraction phase, the resulted cloudy solution was passed through a packed trapping column that was cooled to 0 °C. The temperature of the CCT column was then increased to 25 °C and the surfactant rich phase was desorbed with 400 μL ethanol to be directly injected into HPLC for the analysis. The effects of different variables such as pH, surfactant concentration, cloud point temperature and time were investigated and optimum conditions were established by a central composite design (response surface) method. A limit of detection of 0.066 mg L−1 curcumin and a linear range of 0.22–100 mg L−1 with a determination coefficient of 0.9998 were obtained for the method. The average recovery and relative standard deviation for six replicated analysis were 101.0% and 2.77%, respectively. The CCT-CPE technique was faster than a conventional CPE method requiring a lower concentration of the surfactant and lower temperatures with no need for the centrifugation. The proposed method was successfully applied to the analysis of curcumin in human urine samples. 相似文献
73.
Abdorreza Mohammadi Rouya Tavakoli Marzieh Kamankesh Hamid Rashedi Abdolmohammad Attaran Mostafa Delavar 《Analytica chimica acta》2013
A simple and highly sensitive analytical methodology for isolation and determination of patulin in apple-juice samples, based on enzyme-assisted extraction (EAE) and ionic liquid-based dispersive liquid–liquid microextraction (IL-DLLME) was developed and optimized. Enzymes play essential roles in eliminating interference and increasing the extraction efficiency of patulin. Apple-juice samples were treated with pectinase and amylase. A mixture of 80 μL ionic liquid and 600 μL methanol (disperser solvent) was used for the IL-DLLME process. The sedimented phase was analyzed by high-performance liquid chromatography (HPLC). Experimental parameters controlling the performance of DLLME, were optimized using response surface methodology (RSM) based on central composite design (CCD). Under optimum conditions, the calibration curves showed high levels of linearity (R2 > 0.99) for patulin in the range of 1–200 ng g−1. The relative standard deviation (RSD) for the seven analyses was 7.5%. The limits of detection (LOD) and limits of quantification (LOQ) were 0.15 ng g−1 and 0.5 ng g−1, respectively. The merit figures, compared with other methods, showed that new proposed method is an accurate, precise and reliable sample-pretreatment method that substantially reduces sample matrix interference and gives very good enrichment factors and detection limits for investigation trace amount of patulin in apple-juice samples. 相似文献
74.
Marzieh piryaei 《Natural product research》2016,30(8):991-994
This article investigates the effect of microwaves on the amount of volatile compounds Achillea tenuifolia Lam with two methods, headspace single-drop microextraction and microwave-assisted headspace single-drop microextraction (MA-SDME), for the analysis of essential oil. Solvent selection, solvent volume, microwave power, irradiation time and sample mass were optimised by the simplex method. 相似文献
75.
Seyedeh Marzieh Ghavidel 《Journal of Mathematical Analysis and Applications》2008,345(2):854-870
We investigate the problem of existence and flow invariance of mild solutions to nonautonomous partial differential delay equations , t?s, us=φ, where B(t) is a family of nonlinear multivalued, α-accretive operators with D(B(t)) possibly depending on t, and the operators F(t,.) being defined—and Lipschitz continuous—possibly only on “thin” subsets of the initial history space E. The results are applied to population dynamics models. We also study the asymptotic behavior of solutions to this equation. Our analysis will be based on the evolution operator associated to the equation in the initial history space E. 相似文献
76.
Let be a field, and M and N two finitely generated graded modules over standard graded -algebras A and B, respectively. We will study generalized, sequentially, almost, and approximately Cohen–Macaulay as well as clean, and pretty
clean properties of the -module through the corresponding properties of M and N. The behavior of these properties with respect to the simplicial join of two simplicial (multi)complexes will be revealed
as corollaries. 相似文献
77.
Electrocatalytic Activities of Graphene/Nile Blue Nanocomposite Toward Determination of Hydrogen Peroxide and Nitrite Ion
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Reza Karimi Shervedani Elham Ansarifar Marzieh Samiei Foroushani 《Electroanalysis》2016,28(9):1957-1969
Electrocatalytic activities of graphene nanosheets/Nile blue nanocomposite, synthesized and adsorbed simultaneously on the glassy carbon (GC?GNs?NB) electrode, are investigated. The nanocomposite was characterized by ATR?FTIR, FESEM and voltammetry. Activity of the electrode toward reduction of H2O2 and oxidation of NO2? was studied electrochemically. Values of 1.95 and 0.730 mM are found for the Michaelis?Menten constant of the electrode toward H2O2 and NO2?, respectively. Wide dynamic response ranges were observed for the electrode, with DLs of 0.22 μM H2O2 and 1.1 μM NO2?. Effect of interferences was studied. The sensor was successfully tested for H2O2 and NO2? contents in real samples, respectively. 相似文献
78.
Construction of 5‐amino‐1,10‐phenanthroline‐Fe(II) Nanostructures on Glassy Carbon Electrode: Simultaneous and Selective Determination of Purine and Pyrimidine DNA Bases
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Reza Karimi Shervedani Sedigheh Bagheri Dehaghi Marzieh Samiei Foroushani 《Electroanalysis》2016,28(4):874-880
5‐amino‐1,10‐phenanthroline‐Fe(II) complex is immobilized onto GC electrode and used for determination of DNA bases. Modifications are traced by electrochemical methods. All DNA bases are electroactive on the modified electrode. The Ips increased linearly with increase of DNA bases concentration. A wide response range was observed for each base (~4 orders for guanine (GA) and adenine (A); and ~2.5 orders for thymine (T) and cytosine (C)) with DLs of 0.15, 4.44, 133.0 and 230.0 nM, respectively. The electrode was applied for determination of calf‐thymus DNA bases. The value obtained for [(GA+C)/(A+T)], 0.78, is in good agreement with standard value, 0.77. 相似文献
79.
Synthesis of Oxazolo[5,4‐d][1,2,4]triazolo[4,3‐a]pyrimidines as a New Class of Heterocyclic Compounds
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Marzieh Akbarzadeh Mehdi Bakavoli Hossein Eshghi Ali Shiri 《Journal of heterocyclic chemistry》2016,53(3):832-839
Several new derivatives of oxazolo[5,4‐d]pyrimidine ( 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h ) have been synthesized through the reaction of 2,4‐dichloro‐6‐methyl‐5‐nitropyrimidine ( 2 ) with aryl carboxylic acids in refluxing POCl3. Further treatment of compounds ( 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h ) with hydrazine hydrate gave the hydrazine derivatives ( 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h ) that were subsequently cyclized into a novel heterocyclic system, oxazolo[5,4‐d][1,2,4]triazolo[4,3‐a]pyrimidine ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l , 5m , 5n , 5o , 5p ) and ( 7a , 7b , 7c , 7d ) on treatment with triethylorthoesters or carbondisulfide and alkylhalides, respectively. 相似文献
80.
Ali Benvidi Marzieh Dehghan Tezerjani Afsaneh Dehghani Firouzabadi Mohammad Mazloum-Ardakani Seyed Mohammad Moshtaghioun 《Journal of the Iranian Chemical Society》2016,13(11):2135-2142
In this work, a simple and novel electrochemical biosensor based on a glassy carbon electrode (GCE) modified with graphene oxide nanosheets (GO) was developed for detection of DNA sequences. The morphology of prepared nanoplatform was investigated by scanning electron microscopy, infrared (FTIR) and UV/Vis absorption spectra. The fabrication processes of electrochemical biosensor were characterized with cyclic voltammetry and electrochemical impedance spectroscopy (EIS) in an aqueous solution. The optimization of experimental conditions such as immobilization of the probe BRCA1 and its hybridization with the complementary DNA was performed. Due to unique properties of graphene oxide nanosheets such as large surface area and high conductivity, a wide liner range of 1.0 × 10?17–1.0 × 10?9 M and detection limit of 3.3 × 10?18 M were obtained for detection of BRCA1 5382 mutation by EIS technique. Under the optimum conditions, the proposed biosensor (ssDNA/GO/GCE) revealed suitable selectivity for discriminating the complementary sequences from non-complementary sequences, so it can be applicable for detection of breast cancer. 相似文献