Facile Fabrication of Zirconia Modified Screen‐Printed Carbon Electrodes for Electrochemical Sensing of Phosphate

We report here a facile method to immobilize zirconia nanoparticles on a disposable screen‐printed carbon electrode (designated as ZrO₂‐SPCE) for phosphate sensor application. Simply by ultrasonicating a bare SPCE in a ZrO₂ slurry, ZrO₂ nanoparticles can be immobilized effectively on the electrode surface as verified by surface characterization evidences. Using ferricyanide as a redox probe, an increase in the charge transfer resistance (R_ct) of ferricyanide upon adsorption of phosphate on ZrO₂ is used for the determination of phosphate. This ZrO₂‐SPCE phosphate sensor shows a wide linear range up to 1 mM and a detection limit of 1.69 µM (S/N=3). Practical applicability of the ZrO₂‐SPCE is demonstrated by detecting phosphate content in human blood samples.     

Dual conductance, negative differential resistance, and rectifying behavior in a molecular device modulated by side groups

We investigate the electronic transport properties for a molecular device model constructed by a phenylene ethynylene oligomer molecular with different side groups embedding in a carbon chain between two graphene electrodes. Using the first-principles method, the unusual dual conductance, negative differential resistance (NDR) behavior with large peak to valley ratio, and obvious rectifying performance are numerically observed in such proposed molecular device. The analysis of the molecular projected self-consistent Hamiltonian and the evolution of the frontier molecular orbitals (MOs) as well as transmission coefficients under various external voltage biases gives an inside view of the observed results, which suggests that the dual conductance behavior and rectifying performance are due to the asymmetry distribution of the frontier MOs as well as the corresponding coupling between the molecule and electrodes. But the NDR behavior comes from the conduction orbital being suppressed at certain bias. Interestingly, the conduction properties can be tuned by introducing side groups to the molecule and the rectification as well as the NDR behavior (peak to valley ratio) can be improved by adding different side groups in the device model.     

Rh(II)-catalyzed formation and rearrangement of trifluoroacetyl-containing sulfur ylides

A facile, convenient, efficient, and high yielding Rh(II)-catalyzed formation and rearrangement of trifluoroacetyl-containing sulfur ylides are reported. It is a Rh₂(OAc)₄-catalyzed [2,3]-sigmatropic rearrangement of sulfur ylide intermediates generated from α-diazo compounds.     

Identification and quantification of 13 components in Angelica sinensis (Danggui) by gas chromatography-mass spectrometry coupled with pressurized liquid extraction

Angelica sinensis (Danggui in Chinese), a well-known traditional Chinese medicine, is also used as a health food product for women's care in Europe and America. Therefore, the demand for Danggui is enormous throughout the world. Due to the shortage of Angelica sinensis, Angelica acutiloba and Angelica gigas are commonly used as the substitutes of Danggui in the market of southeast Asia. However, the three common Angelica roots showed variation in their genetic and chemical composition. Up to date, it is thought that ferulic acid, ligustilide and other phthalides such as butylidenephthalide are the biologically active components of Danggui. In this paper, the contents of 13 compounds including ferulic acid, Z-ligustilide, E-ligustilide, Z-butylidenephthalide, E-butylidenephthalide, 3-butylphthalide, 3-butylidene-4-hydroxyphthalide, senkyunolide A, 6,7-epoxyligustilide, senkyunolide F, senkyunolide H, senkyunolide I, and 6,7-dihydroxyligustilide were determined or estimated by using gas chromatography-mass spectrometry (GC-MS) coupled with pressurized liquid extraction (PLE). The results showed that GC-MS coupled with PLE offered a simple, rapid and high sensitive method to analysis of components in Angelica root. And the contents of investigated compounds in Angelica sinensis, Angelica acutiloba and Angelica gigas, which are used as Danggui in China, Japan and Korea, respectively, were highly variant. It is thought that interaction of multiple chemical compounds contributes to the therapeutic effects of Chinese medicines. However, the overall clinical efficacy of these different Danggui has not been determined. Therefore, comparison of chemical components and pharmacological activities of different Angelica root is helpful to elucidate the mechanism of therapeutic effects of Danggui.     

Liquid Chromatographic Determination of NSAIDs in Urine After Dispersive Liquid–Liquid Microextraction Based on Solidification of Floating Organic Droplets

An environmentally benign method of sample preparation based on dispersive liquid–liquid microextraction and solidification of floating organic droplets (DLLME-SFO) coupled with high-performance liquid chromatography with ultraviolet detection has been developed for analysis of non-steroidal anti-inflammatory drugs (NSAIDs) in biological fluids. A low-toxicity solvent was used to replace the chlorinated solvents commonly used in conventional DLLME. Seven conditions were investigated and optimized: type and volume of extraction solvent and dispersive solvent, extraction time, effect of addition of salt, and sample pH. Under the optimum conditions, good linearity was obtained in the range 0.01–10 µg mL⁻¹, with coefficients of determination (r ²) >0.9949. Detection limits were in the range 0.0034–0.0052 µg mL⁻¹ with good reproducibility (RSD) and satisfactory inter-day and intra-day recovery (95.7–115.6 %). The method was successfully used for analysis of diclofenac, mefenamic acid, and ketoprofen in human urine. Analysis of urine samples from a patient 2 and 4 h after administration of diclofenac revealed concentrations of 1.20 and 0.34 µg mL⁻¹, respectively.

     

有序介孔硅片粒子表面的修饰及其表征

采用溶胶-凝胶的方法制备了粒径在50~300nm,具有正六边形的介孔二氧化硅片,用1,6-己二异氰酸酯(hexamethylene diisocyanate,HDI)对有序介孔硅片粒子表面进行有机化修饰,使其表面接枝能够参与反应的N=C=O活性基团。用FTIR、热重分析、TEM等分析方法对修饰后的有序介孔硅片粒子进行了表征,以确定HDI接在了有序介孔硅片粒子的表面。     

Synthesis and application of mesoporous molecular sieve for miniaturized matrix solid‐phase dispersion extraction of bioactive flavonoids from toothpaste,plant, and saliva

This article describes the use of the mesoporous molecular sieve KIT‐6 as a sorbent in miniaturized matrix solid‐phase dispersion (MSPD) in combination with ultra‐performance LC for the determination of bioactive flavonoids in toothpaste, Scutellariae Radix, and saliva. In this study, for the first time, KIT‐6 was used as a sorbent material for this mode of extraction. Compared with common silica‐based sorbents (C18 and activated silica gel), the proposed KIT‐6 dispersant with a three‐dimensional cubic Ia3d structure and highly ordered arrays of mesoporous channels exhibits excellent adsorption capability of the tested compounds. In addition, several experimental variables, such as the mass ratio of sample to dispersant, grinding time, and elution solvent, were optimized to maximize the extraction efficiency. The proposed analytical method is simple, fast, and entails low consumption of samples, dispersants and elution solvents, thereby meeting “green chemistry” requirements. Under the optimized conditions, the recoveries of three bioactive flavonoids obtained by analyzing the spiked samples were from 89.22 to 101.17%. Also, the LODs and LOQs for determining the analytes were in the range of 0.02–0.04 μg/mL and 0.07–0.13 μg/mL, respectively. Finally, the miniaturized matrix solid‐phase dispersion method was successfully applied to the analysis of target solutes in real samples, and satisfactory results were obtained.     

Optically Active Helical Vinylterphenyl Polymers: Chiral Teleinduction in Radical Polymerization and Tunable Stereomutation

Helical vinyl aromatic polymers are emerging as interesting chiral materials due to their dynamic tailorability, synthetic simplicity, and outstanding chemical and physical stabilities. This Personal Account discusses long‐range chirality transfer in the radical polymerization of vinylterphenyl monomers and tunable stereomutation of the resultant polymers. It begins with a general introduction to the design, synthesis, and characterization of helical poly{(+)‐2,5‐bis[4′‐((S)‐2‐methylbutyloxy)phenyl]styrene}, the first one of this series of polymers. Then, long‐range chirality transfer during radical polymerization of terphenyl‐based vinyl monomers is explained. After that, the chiroptical property control of the resultant polymers by means of the transition from kinetically controlled conformation to thermodynamically controlled conformation and external stimulus is described. This Personal Account concludes by discussing the advantages and disadvantages of the strategy of using vinylterphenyls to obtain optically active helical polymers and providing a short outlook, especially emphasizing the importance of tacticity on the chiroptical properties of polymers.     

Determination of pesticides in water by cone-shaped membrane protected liquid phase microextraction prior to micro-liquid chromatography

A new sample pre-treatment technique termed cone-shaped membrane liquid phase microextraction (CSM-LPME) was developed and combined with micro-liquid chromatography (micro-LC) for the determination of selected pesticides in water samples. Four pesticides (hexaconazole, procymidone, quinalphos and vinclozolin) were considered as target analytes. Several important extraction parameters such as types of extraction solvent, agitation rate, pH value, total exposure time and effect of salt and humic acids were optimized. Enrichment factors of > 50 folds were easily achieved within 20 min of extraction. The analytical data demonstrated relative standard deviations for the reproducibility of the optimized CSM-LPME method ranging from 6.3 to 7.5%. The correlation coefficients of the calibration curves were at least 0.9995 across a concentration range of 2-100 microg/L. The detection limits for all the analytes were found to be in the range of 1.1-1.9 microg/L.     

Supramolecular isomerism in the hydrogen-bonded network of (5<Emphasis Type="Italic">R</Emphasis>,10<Emphasis Type="Italic">R</Emphasis>)-3,8-dihydroxy-5,10-diethoxy-5,10-dihydrochromeno[5,4,3-<Emphasis Type="Italic">cde</Emphasis>]chromene monohydrate

A new compound (5R, 10R)-3,8-dihydroxy-5,10-diethoxy-5,10-dihydrochromeno[5,4,3-cde]chromene monohydrate was obtained from 3,4-dihydroxybenzaldehyde in aerobic basic aqueous ethanol solution in the presence of manganese chloride and triethylamine and crystallized in orthorhombic P2₁2₁2₁ space group (denoted as 1). When 1 was recrystallized from aqueous methanol, it was transformed to another crystal (2) with the same composition but in P2₁/n space group. The drastic difference in the extensive hydrogen bond network makes 1 a 3D and 2 a 2D infinite supramolecular structure, respectively.