Development of an Efficient Solid-Phase Microextraction Monolithic Column for the Analysis of Estrogens in Human Urine and Serum Samples

Estrogen plays a crucial role in various stages of human development and is present in the human body at trace level; therefore, an efficient strategy for the quantitative analysis of trace estrogens is required. However, this analysis is complicated by the presence of extremely complex biological matrices. To address this challenge, a novel method based on monolithic column solid-phase microextraction and ultra-high-performance liquid chromatography-tandem mass spectrometry was developed for the sensitivity analysis of six estrogens: β-estradiol, α-estradiol, 17α-ethynylestradiol, estrone, diethylstilbestrol, and hexestrol, in human urine and serum samples. The method exhibits a low limit of detection (8.6–37 ng L^?1), with wide linear ranges (0.10–25 μg L^?1) for each analyte and remarkable correlation coefficients (R²?=?0.9953–0.9995). The developed method was successfully used to detect estrogens in urine and serum samples. The six analytes were satisfactorily recovered between 76.2 and 107% with relative standard deviations ranging from 2.5 to 8.3% (n?=?3). The results demonstrated that the developed method, based on a poly(methacrylic acid/3-acrylamidophenylboronic acid-co-ethylene glycol dimethacrylate) monolithic column, is an effective enrichment approach toward the analysis of trace estrogens in human urine and serum samples.

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晶体学14种空间点阵型式的对称性分析与导出

依据7个晶系的特征对称元素和正当点阵单位的划分规则，分析了各晶系空间点阵型式的生成过程，从而确定晶体学14种空间点阵型式（简立方（cP）、体心立方（cI）、面心立方（cF）、简六方（hP）、简四方（tP）、体心四方（t1）、R心六方（hR）、简正交（oP）、C心正交（oC）、体心正交（oI）、面心正交（oF）、简单斜（mP）、C心单斜（mC）和简三斜（aP）是合理的逻辑演绎结果。     

Pd/C-catalyzed Reductive Mono-N-alkylation of Nitrophenol Derivatives in One-pot Way

A range of different nitrophenol derivatives were converted in one‐pot to the corresponding secondary alkyl aminophenols in good to excellent yields by using ketones as alkyl source and hydrogen over 10 wt% Pd/C as reducing agent. In all examples, except for one, the secondary amine was the sole alkylation product isolated. When aldehydes were used as alkyl source, the corresponding tertiary amine as a sole alkylation product was isolated.     

Ultrasensitive detection of the reduced form of nicotinamide adenine dinucleotide based on carbon nanotube field effect transistor

We developed a simple, ultrasensitive, and quantitative detection method for the reduced form of nicotinamide adenine dinucleotide (NADH), based on carbon nanotube field effect transistors (CNTFETs). Following the injection of NADH at different concentrations, we obtained different electrical signals from a semiconductor characterization system mimicking biological catalysis of NADH dehydrogenase (CoI). Here, FET was fabricated via photolithography, attaching silicon wells, as the detection chamber, on the channel area of the single wall carbon nanotube (SWCNT). SWCNTs were functionalized with phenazine derivant, a counterpart of the key functional prosthetic group of CoI enzyme. In the presence of NADH, electrons transferred to phenazine derivant through SWCNT, by analogous means of the electron transport chain formed by a series of iron-sulfur (FeS) clusters in CoI. Using this method, the limit of detection was as low as 1 pM, and the range of linear response was 10 pM to 500 nM. Significantly, this approach possesses great potential for applications in real-time detection of NADH at extremely low concentrations, and rigorous analysis for NADH in electrochemical fields.     

Core–Shell Structured Polystyrene/BaTiO3 Hybrid Nanodielectrics Prepared by In Situ RAFT Polymerization: A Route to High Dielectric Constant and Low Loss Materials with Weak Frequency Dependence

A novel route to prepare core–shell structured nanocomposites with excellent dielectric performance is reported. This approach involves the grafting of polystyrene (PS) from the surface of BaTiO₃ by an in situ RAFT polymerization. The core–shell structured PS/BaTiO₃ nanocomposites not only show significantly increased dielectric constant and very low dielectric loss, but also have a weak frequency dependence of dielectric properties over a wide range of frequencies. In addition, the dielectric constant of the nanocomposites can also be easily tuned by varying the thickness of the PS shell. Our method is very promising for preparing high‐performance nanocomposites used in energy‐storage devices.     

Partial oxidation of propene on oxygen-covered Au(111)

Partial oxidation of propene is promoted by Au following deposition of atomic oxygen (0.3 ML) via O3 decomposition on Au(111) at 200 K. Several partial oxidation products--acrolein, acrylic acid, and carbon suboxide (O=C=C=C=O)-are produced in competition with combustion to CO2 and H2O. Acrolein is the primary partial oxidation product, and it is further oxidized to the other products by excess oxygen. We propose that acrolein is derived from allyloxy intermediate that is formed via insertion of oxygen into the allylic C-H bond. While no propene epoxide formation is detected from oxidation of C3H6, a small amount of epoxidation is observed during reaction of C3D6 and CD3CH=CH2. These results are strong indications that small changes in the energy required for allylic C-H activation, in this case due to a kinetic isotope effect, may dramatically change the selectivity; thus, small modifications of the properties of oxygen on Au may lead to the more desirable epoxidation process. Our results are discussed in the context of the origin of activity of Au-based catalysts.     

Correlation between rheological,electrical, and microstructure characteristics in polyethylene/aluminum nanocomposites

Polyethylene (PE)/aluminum (Al) nanocomposites with various filler contents were prepared by a solution compounding method. We investigated the influence of the surface modification of Al nanoparticles on the microstructure and physical properties of the nanocomposites. The silane coupling agent octyl‐trimethoxysilane was shown to significantly increase interfacial compatibility between the polymer phase and Al nanoparticles. Rheological percolation threshold values were determined by analyzing the improvement in storage modulus at low frequencies depending on the Al loadings. Lower percolation threshold values were obtained for the composites prepared with the original nanoparticles than those prepared with the silane‐modified Al nanoparticles. A strong correlation between the time and concentration dependences of dc conductivity and rheological properties was observed in the different nanocomposite systems. The rheological threshold of the composites is smaller than the percolation threshold of electrical conductivity for both of the nanocomposite systems. The difference in percolation threshold is understood in terms of the smaller particle–particle distance required for electrical conduction when compared with that required to impede polymer mobility. It was directly shown by SEM characterization that the nanoparticle surface modification yielded better filler dispersion, as is consistent with our rheological and electrical analysis. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2143–2154, 2008     

无铬CO高温变换催化剂的研究Ⅱ.过渡元素对高变催化剂结构与性能的影响

通过ＸＲＤ，ＢＥＴ和ＸＰＳ表征及反应性能测定表明，铁系高变催化剂中加入的过渡元素能够进入Ｆｅ３Ｏ４晶格形成固溶体，并使催化剂的晶胞参数随着加入元素离子半径的增大而增大，晶粒度明显变小，比表面积增大，起到铬的作用，催化剂的活性和热稳定性提高．发现部分过渡元素具有富集ＯＨ－的特性，使催化剂在较低的汽／气比条件下具有较高的催化活性．研制成功的Ｂ１２１型无铬高变催化剂性能达到铁铬系高变催化剂的技术指标．