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The dependence of Mentha pulegium L. (pennyroyal) essential oil composition, obtained by supercritical carbon dioxide (SC-CO2), with the following parameters: pressure, temperature, extraction time (dynamic), and modifier (methanol) was studied. The results were also compared with those obtained by conventional hydrodistillation method in laboratory conditions. Regarding the percentages of menthone (30.3%) and pulegone (52.0%), the optimum SFE results were obtained at the following experimental conditions: pressure=100 atm, T=35 °C, dynamic time=10 min, and Vmodifier=0 μl. The results of hydrodistillation showed that the major components of M. pulegium L. were pulegone (37.8%), menthone (20.3%), and piperitenone (6.8%). The evaluation of the composition of each extract was performed by gas chromatography-mass spectrometry. 相似文献
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Graphene quantum dot-β-cyclodextrin modified glassy carbon electrode was used as a new nanosensor for determination of L-tyrosine (L-Tyr). It was found that graphene quantum dot-β-cyclodextrin has been stably electrodeposited on glassy carbon electrode modified by simple technique. The cyclic voltammograms of the modified electrode in an aqueous solution displayed a pair of well-defined, stable and irreversible reductive/oxidation redox systems. The apparent electron transfer rate constant (ks) and transfer coefficient (α) determined by cyclic voltammetry were approximately equal to 8.0 s–1 and 0.7, respectively. The modified electrode showed excellent catalytic activity towards the oxidation of L-Tyr at positive potential in buffer solution. The nanosensor also displayed fast response time, high sensitivity, low detection limit and a remarkably positive potential oxidation of L-Tyr that decreased the effect of interferences in analysis. 相似文献
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A heterogeneous magnetic copper catalyst was prepared via anchoring of copper sulfate onto multi‐layered poly(2‐dimethylaminoethyl acrylamide)‐coated magnetic nanoparticles and was characterized using various techniques. The catalyst was found to be active, effective and selective for one‐pot three‐component reaction of alkyl halide, sodium azide and alkyne, known as copper‐catalyzed click synthesis of 1,2,3‐triazoles. As little as 0.3 mol% of catalyst was found to be effective under the optimum conditions. The catalyst could also be recycled and reused up to seven times without significant loss of activity. Thermal stability, high loading level of copper on catalyst, broad diversity of alkyl/benzyl/allyl bromide/chloride and alkyl/aryl terminal alkynes without isolation of azide intermediate, and good to excellent yields of products make this procedure highly economical. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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A. N. Golikand J. B. Raoof M. Baghayeri M. Asgari L. Irannejad 《Russian Journal of Electrochemistry》2009,45(8):881-886
The catalytic behaviour of glassy carbon electrode modified by 1,2-dihydroxy antraquinone (Alizarin) was investigated. The electrocatalytic ability of modified electrode for the reduction of dioxygen was examined by cyclic voltammetry and rotating disk electrode (RDE) voltammetry techniques. The Alizarin modified glassy carbon electrode possesses excellent electrocatalytic abilities for dioxygen reduction over potential 400 mV lower than at the bare glassy carbon electrode. Hydrodynamic studies were performed to determine the heterogeneous rate constant for the reduction of O2 at the surface of modified electrode. It was determined by Koutecky-Levich plot. The apparent diffusion coefficient of O2 in O2 saturated acidic solutions was estimated by using Levich equation. Studies show the involvement of four electrons in dioxygen reduction at the surface of this modified electrode. 相似文献
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Shahnaz Rostamizadeh Ali Mohammad Amani Reza Aryan Hamid Reza Ghaieni Nasrin Shadjou 《合成通讯》2013,43(20):3567-3576
A simple, inexpensive, and efficient one-pot synthesis of 2,3-dihydroquinazoline-4(1H)-one derivatives under solvent-free conditions using a catalytic amount of iodine with excellent product yields is reported. This methodology provides easy, quantitative access to various 2,3-dihydroquinazoline-4(1H)-one derivatives, using commercially available iodine as a catalyst. 相似文献
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Kinetics of the addition reaction of triphenylphosphine to para‐benzoquinone in 1,2‐dichloroethane as solvent was studied. Initial rate method was used to determine the order of the reaction with respect to the reactants. Pseudo‐first‐order method was also used to calculate the rate constant. This reaction was monitored by UV‐vis spectrophotometry at 520 nm by variable time method. On the basis of the obtained results, the Arrhenius equation of this reaction was obtained: The activation parameters, Ea, ΔH#, ΔG#, and ΔS# at 300 K were 5.701, 6.294, 19.958 kcal mol?1 and ?45.853 cal mol?1 K?1, respectively. This reaction is first and second order with respect to triphenylphosphine and para‐benzoquinone, respectively. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36:472–479, 2004 相似文献
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A. N. Golikand J. Raoof M. Baghayeri M. Asgari L. Irannejad 《Russian Journal of Electrochemistry》2009,45(2):192-198
The electrocatalytic oxidation of methanol studied at the surface of nickel disc electrode coated with N,N-bis(salicylidene)phenylenediamine (Salophen) legend in 0.10 M NaOH solution using cyclic voltammetry. The results showed that
the Ni-salophen layer formed at the surface of electrode behaves as an efficient electrocatalyst for the oxidation of methanol
in alkaline medium. The thermal analysis of Ni-salophen complex studied at temperature ranges 0–800°C in argon atmosphere.
Also, FTIR was employed to prove the formation of complex on the modified electrode surface. Moreover, the effects of various
parameters such as oven temperature, methanol concentration, NaOH concentration and media temperature on electro-oxidation
of methanol were investigated. The kinetic parameters such as activation energy and Tafel slope were calculated for methanol
oxidation on the modified electrode surface.
Published in Elektrokhimiya in Russian, 2009,, 2009, Vol. 45, No. 2, pp. 203–210.
The text was submitted by author in English. 相似文献
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Mojtaba Shamsipur Mehdi Asgari Mir Fazlollah Mousavi Reza Davarkhah 《Electroanalysis》2012,24(2):357-367
MWCNTs‐nanoNiO composite was used as a glassy carbon electrode modifier for construction of a novel catalase nanobiosensor for hydrogen peroxide. The immobilized catalase exhibited excellent electrocatalytic activity towards the reduction of H2O2. The resulting amperometric biosensor exhibited a linear response over a concentration range of 200 µM to 2.53 mM with a low detection limit of 19.0 µM. Electrochemical impedance measurements revealed that the modified electrode can be used for the sensitive detection of H2O2. The charge transfer resistance found to decrease significantly after enzymatic reaction of nanobiosensor with H2O2. The resulting impedance was highly sensitive to H2O2 over a linear range of 19–170 nM with a detection limit of 2.4 nM. 相似文献