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991.
A room temperature ionic liquid N‐butylpyridinium hexafluorophosphate (BPPF6) was used as a binder to make an ionic liquid modified carbon paste electrode (IL‐CPE), which showed good characteristics such as simple preparation procedure, fast electrochemical response and good conductivity. The electrochemical oxidation of ascorbic acid (AA) on the new IL‐CPE was carefully studied. The oxidation peak potential of AA on the IL‐CPE appeared at 109 mV (vs. SCE), which was about 338 mV decrease of the overpotential compared to that obtained on the traditional carbon paste electrode (CPE) and the oxidation peak current was increased for about four times. The electrochemical parameters of AA on the IL‐CPE were calculated with the charge transfer coefficient (α) and the electrode reaction rate constant (ks) as 0.87 and 0.800 s?1, respectively. Based on the relationship of the oxidation peak current and the concentration of AA a sensitive analytical method was established with cyclic voltammetry. The linear range for AA determination was in the range from 1.0×10?5 to 3.0×10?3 mol/L with the linear regression equation as Ip (μA)=?2.52–0.064C (μmol/L) (n=13, γ=0.9942) and the detection limit was calculated as 8.0×10?6 mol/L (3σ). The proposed method was free of the interferences of coexisting substances such as dopamine (DA) and amino acids etc., and successfully applied to the vitamin C tablets determination. 相似文献
992.
Ariza-Castolo A Montalvo-González JA Montalvo-González R 《Magnetic resonance in chemistry : MRC》2005,43(12):975-978
The configurational properties of a series of cyclohexylidene imines are discussed on the basis of their 1H, 13C and 15N NMR spectral data. 相似文献
993.
Cobas JC Constantino-Castillo V Martín-Pastor M del Río-Portilla F 《Magnetic resonance in chemistry : MRC》2005,43(10):843-848
(1)H NMR scalar coupling constants are a rich source of information on molecular structure, but their extraction from spectra can be less than straightforward. Previous approaches to J extraction include methods proposed by Hoye, Golotvin, and the 'modified J-doubling' method. Here we describe the ACCA method, currently implemented in the NMR package MestReC, which allows a high degree of automation in the extraction of coupling patterns even in the case of complex multiplets with sublinewidth splitting. The new approach is illustrated by application to strychnine, for which it has detected previously unreported couplings. 相似文献
994.
The reactivity of a Cr‐Te multilayer film consisting of 326 Cr/Te double‐layers with about 88(3) at% Te was investigated with in‐situ X‐ray diffraction. The occurrence of a superstructure reflection caused by the multilayer system is observed. During the annealing procedure between 80 and 90 °C the layer‐by‐layer arrangement is destroyed and elemental Te crystallizes. After 6 h isothermal annealing at 140 °C CrTe3 starts to crystallize. The amount and the crystal size of CrTe3 increase with raising temperature and Te is consumed during the growth process. At 220 °C the formation of crystalline Cr2Te3 is observed and between 220 and 260 °C CrTe3 is completely decomposed into Cr2Te3. The two Cr tellurides grow as highly textured materials. The size of CrTe3 crystals is significantly larger than that of Cr2Te3. For a co‐deposited Cr‐Te film with composition 77(3) at% Te the tri‐telluride and elemental Te crystallize simultaneously. The texture of CrTe3 is less pronounced and different reflections of the tri‐telluride occur besides the (h00)‐reflections. Up to 160 °C a pronounced increase of the crystallite size is observed and the crystals are significantly larger than those obtained with the multifilm sample. At 130 °C the crystallization kinetics seem to be controlled by nucleation. 相似文献
995.
Grace‐Ann M. Lobo Sneha A. Chitre Spandan M. Rathod Robert B. Smith Ray Leslie Callum Livingstone James Davis 《Electroanalysis》2007,19(24):2523-2528
The exploitation of 2‐bromo‐1,4‐naphthoquinone (NQBr) as a selective redox label for the determination of reduced thiol functionalities (RSH) has been investigated. The system is selective for RSH functionality, giving distinct voltammetric signals for glutathione and cysteine but can also be adapted for broad spectrum thiol detection. Ion chromatographic protocols based on conductimetric detection enable total RSH analysis (protein and monomolecular moieties) within human plasma. Bromide released through the reaction can be easily quantified and integrated within normal IC measurements. The efficacy of the approach has been assessed and the response validated through comparison with the standard colorimetric technique. 相似文献
996.
Although a number of computational studies have examined the relative stability of icosahedral and decahedral gold clusters from 1 to 3 nm in size, few studies have focussed on the variety of face-centered cubic (fcc) nanoparticles in this size regime. In most cases small fcc gold particles are assumed to adopt the truncated octahedral shape, but in light of the fact that the shape and structure of gold nanoparticles is known to vary, the relative stability of fcc polyhedra may change with size. Presented here are results of first-principles calculations investigating the preferred shape of gold particles less than 3 nm in size. Our results indicate that the equilibrium shape of fcc gold nanoparticles less than 1 nm is the cuboctahedron, but this shape rapidly becomes energetically unstable with respect to the truncated octahedron, octahedron and truncated cube shapes as the size increases. 相似文献
997.
本文提出一种新型的离子色谱方法,采用恒电流电场代替机械泵输送离子,研制出体积小、重量轻、成本低、易操作的电迁移微离子色谱仪,并检测了几种常见的阴离子,Cl~-、Br~-、NO_2~-的检测极限为10~(-11)~10~(-12)mol,峰高和保留时间重现性相对标准偏差均<3%,进样量与峰高的线性关系良好。 相似文献
998.
Giovanni Zocchi 《Chemphyschem》2006,7(3):555-560
One common strategy for the detection of biomolecules is labeling either the target itself or an antibody that binds to it. Herein, a different approach, based on detecting the conformational change of a probe molecule induced by binding of the target is discussed. That is, what is being detected is not the presence of the target or the probe, but the conformational change of the probe. Recently, a single-molecule sensor has been developed that exploits this mechanism to detect hybridization of a single DNA oligomer to a DNA probe, as well as specific binding of a single protein to a DNA probe. Biomolecular recognition often involves large conformational changes of the molecules involved, and therefore this strategy may be applicable to other assays. 相似文献
999.
《Electroanalysis》2006,18(22):2202-2209
A simple and rapid method has been developed for the analysis of four nonsteroidal anti‐inflammatory drugs (NSAIDs) in serum using microchip capillary electrophoresis with pulsed amperometric detection. The selected NSAIDs (salicylic acid, acetaminophen, diflunisal, and diclofenac) are among the most commonly used drugs to treat fever, inflammation, and pain. Used above the therapeutic levels, these drugs can cause a wide variety of adverse effects and their fast analysis could have a significant impact in treatment and recovery of the patients. Several conditions, including separation potential, pH, and concentration of the electrolyte solution were studied to optimize the separation and detection. In this study, salicylic acid, acetaminophen, diflunisal, and diclofenac were separated in less than 2 minutes using a 5 mM borate buffer at pH 11.5 and a separation potential of +1200 V. Linear relationships were obtained between the concentration and peak current in the 0.5–15.3 μg/mL range and detection limits around 0.26 μg/mL. After 30 consecutive injections, the stability of both the response and migration time of the analytes showed relative related deviations of less than 4.6% and 1.0%, respectively. The potential of this method was verified by spiking a bovine serum sample with the four NSAIDs and analyzing the recovery ratio. 相似文献
1000.