Improvement of Pulse Amperometric Detection Integrated Automated Flow Injection Analysis of Ethylenethiourea Determination

Improvement of pulse amperometric detection (PAD) method is demonstrated in determination of ethylenethiourea (imidazolidine‐2‐thione, ETU). The anodic detection of ETU will produce polymeric film on an electrode leading to an inactive electrode surface. Here, the PAD method was used to remove the polymeric film formed on the electrode surface between ETU detection. Further, the scheme was integrated with automated flow injection analysis (AFIA) for determining ETU. The operational parameters of PAD in the AFIA system were discussed thoroughly. The analytical characteristics of the system were evaluated at optimum conditions. The linear range of calibration plot was between 20 to 300 μM (the correlative coefficient, r = 0.999) and the detection limit was 0.9 μM (S/N = 3). The relative standard deviations of detection of 50 μM ETU were 0.82% with and 9.07% without PAD scheme. The results indicate the system is a very promising tool for ETU determination. Finally, the matrix effects of two water samples that were collected from a campus and a farm show good recoveries of 92% and 96%.     

气相硝酸及过氧亚硝酸的结构和光电子能谱

采用了B3LYP方法和6-311G(d) 基组，并辅以MP2方法详细地计算了硝酸(HONO2)和过氧亚硝酸(HOONO)及相应正离子的各种可能构象、能量、振动频率等，分析了它们的相对稳定性、电离势、光电子能谱，探讨了用光电子能谱去探测HOONO的可能性.结构优化结果表明， HOONO和HOONO＋均有三种稳定的构象， HOONO有三个一阶鞍点的结构.作出了HOONO和HOONO＋的能量随O－O键旋转的变化曲线图，定性地讨论了可能存在的物种以及各构象之间几何结构的变化.     

Size Effect of Colloidal Selenium Particles on the Inhibition of LPS‐Induced Nitric Oxide Production

We have studied the size‐dependent inhibition capabilities of colloidal selenium (Se) particles on lipopolysaccharide (LPS)‐induced nitric oxide (NO) production in RAW 264.7 cells. Four particle sizes of the nano‐Se, ranging from 45 ? 220 nm in diameter, were examined. All of them, unlike their bulk material, show clear capabilities of inhibition and a trend dependent on the particles size. The inhibition becomes more potent as the particle size increases. It indicates that pursuing the reduction of colloidal sizes into nanoscale is not favoured in this biological system.     

Ytterbium triflate-assisted catalytic oxidative cross-coupling of 2-naphthol derivatives

The oxidative coupling of 2-naphthol and 3-hydroxy-2-naphthoate derivatives with a copper catalyst under an O₂ atmosphere was carried out. The reaction in the presence of a catalytic amount of the Lewis acid, Yb(OTf)₃, proceeded in a cross-coupling specific manner.     

Synthesis of Phenylalanine Analogs

A straightforward synthesis of phenylalanine analogs is described. Cerium ammonium nitrate (CAN) mediated addition of azide to cinnamic ester, followed by reaction with sodium acetate afforded the α‐azidocinnamate in moderate yield. Hydrogenation of α‐azidocinnamate, followed by BOC, CBZ or Fmoc protection gave phenylalanine analogs. A new approach for synthesizing racemic p‐boronophenylalanine analog was also explored.     

固相萃取/液相色谱串联质谱法测定水果中的赤霉素GA3残留

赤霉素是双萜类植物激素,对蔬菜、水果等有显著的增产作用.它属于低毒植物生长调节剂,美国、日本等国规定水果、蔬菜中赤霉素最高残留限量为0.2 μg/g[1],而我国目前还没有相关的国家标准,有必要建立高灵敏、快速的赤霉素残留检测方法[2-3].本文采用固相萃取技术对样品进行处理,以液相色谱串联质谱为检测手段,建立了测定水果中赤霉素GA3残留的新方法,可以为确定赤霉素残留标准提供实验依据.     

Kinetic of Adsorption of Urea Nitrogen onto Chitosan Coated Dialdehyde Cellulose under Catalysis of Immobilized Urease

The adsorption of urea nitrogen onto chitosan coated dialdehyde cellulose (CDAC) under catalysis of immobilized urease in gelatin membrane (IE) was studied in batch system. The pseudo first-order and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model.     

煤焦外表面分形维数在燃烧过程中的变化

煤燃烧的化学反应及其物质输运过程均具有非线性动力特征，燃烧过程是孔洞分形体的变化过程，其外表面结构的变化部分的反映出颗粒内部孔结构的变化过程，本文利用分形理论及其相关的图像处理方法对不同煤种，不同燃烧阶段煤焦外表面结构的SEM图像进行研究，研究结果表明，XIE法较适合计算煤焦表面分形维数，在燃烧过程中煤焦的外表面分形数呈现两种变化趋势，通过最小二乘法多项式拟合确定煤焦外表面分形维数与燃尽率之间的关系式，并得到不同煤种的方程参数。     

Coordination polymers of silver(I) with bis(N-heterocyclic carbene): Structural characterization and carbene transfer

Reactions of the ethylene- and methylene-bridged bis(imidazolium) salts with an equivalent amount of silver oxide in dichloromethane at room temperature produced readily the silver NHC compounds [Ag₂LBr₂]. These compounds are partially soluble in DMF. The X-ray structure determination on 3d (L = 1,1′-dibenzyl-3,3′-ethylenediimidazolin-2,2′-diylidene) reveals the formation of bromide bibridged (Ag₂LBr₂)_n chains and a unique supramolecular motif with weak Ag?Ag interactions of 3.429 Å. Similar to monomeric silver(I) NHC complexes, the silver coordination polymers can also act as carbene transfer reagents for the formation of chelating palladium NHC complexes in excellent yields.     

Improved fluorimetric determination of dissolved aluminium by micelle-enhanced lumogallion complex in natural waters

A modification of the aluminium-lumogallion fluorescence measurement in the presence of the non-ionic surfactant Triton X-100 is presented. The detection limit for dissolved Al is 0.7 nM, with a relative standard deviation of 3.6% at an Al level of 5.0 nM. Compared with previously reported methods in the literature, the method described here is free from matrix effects and can be used for the determination of aluminium in fresh, estuarine and saline waters. The interferences from iron and fluoride were minimized by the addition of o-phenanthroline and Be2+, respectively. The analysis of NIST SRM 1643C and PRC standard 2430101 by the proposed method provides results consistent with the certified values. A successful inter-laboratory calibration exercise also demonstrates the merit of the proposed method for the determination of Al in environmental and marine sciences.