Switchable solvent based liquid phase microextraction of palladium coupled with determination by flame atomic absorption spectrometry

A switchable solvent-based micro-extraction method for pre-concentration and separation of ultratrace palladium was developed prior to its flame atomic absorption spectrometric detection. Reverse change of hydrophilicity of N,N-dimethylcyclohexylamine (DMA) was achieved by reaction with carbonated water. The hydrophilic bicarbonate salt of the protonated DMA was used as extractant for palladium complexed with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). Formation of the hydrophobic form of switchable solvent from hydrophilic form of switchable solvent phase was achieved by addition of sodium hydroxide into the extractant-sample solution. The effect of key parameters affected extraction recovery was studied and optimised by using Plackett–Burman design, central composite design and three dimension (3D) surfaces response. The calibration plot was linear in the range 0.015–1.6 mg L^?1 of palladium with a correlation coefficient of 0.999. The limit of detections values of palladium for liquid and solid samples were 4.28 μg L^?1 and 0.54 µg g^?1, respectively. The pre-concentration factor was 37.5. The accuracy was confirmed by determination of palladium in certified reference material. The procedure was also applied for determination of palladium content of real samples as automotive catalytic converter, roadside dust, sea water and river water.     

Double-stranded ladderphanes with C2-symmetric planar chiral ferrocene linkers

Eight ladderphanes with C₂-symmetric planar chiral ferrocene linkers are synthesized by ring opening metathesis polymerization of bisnorbornene monomers using Grubbs-I catalyst. The aminobenzoate in both monomers and polymers shows absorption maximum around 320 nm. Both monomers and polymers are Circular dichroism (CD) active. Little enhancements of CD profiles around 320 nm are observed for ladderphanes having chiral chloro- or phenyl-substituted ferrocene linkers. However, ladderphanes with a phenyl substituent on the cyclopendienyl ring exhibits enhancement of CD curves aound 240–300 nm. The congested phenyl moieties in adjacent linkers in this polymer might be well oriented such that interactions between these aromatic substituents on different monomeric units might provoke the enhancement of the CD curves in this region. When the methyl-substituted cyclopendienyl ligand is used for chiral ferrocene linkers, the ladderphanes exhibit two-fold enhancement of CD spectrum around 320 nm. This enhancement is further increased when the cyclopentadienyl ligand contains an additional phenyl substituent, owing to exciton coupling between aminobenzoate moieties in adjacent monomeric units. Moreover, the intensity of the CD curves in the region of 240–300 nm is significantly increased. These results suggest that the later polymer may adopt a posible helical structure. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2999–3010     

[4 1]及[3 2]会聚式四氢呋喃环合成策略在天然产物全合成中的应用进展

四氢呋喃环广泛存在于具有生物活性的天然产物结构当中,立体选择性地构筑四氢呋喃环往往成为这些天然产物全合成研究中的关键。本文归纳了已有全合成报道中的四氢呋喃环成环策略,以实例展示了其中的会聚式合成策略在近年的发展。相比于直线型的分子内关环策略,以[4+1]、[3+2]为代表的会聚式四氢呋喃关环策略往往能够使全合成的整体路线更加简洁高效,更符合全合成研究领域的发展趋势。     

原子荧光光谱法测定萤石中的微量铅

以铁氰化钾–盐酸羟胺体系代替铁氰化钾–草酸体系,建立原子荧光法测定萤石中铅含量的方法。对实验条件进行了优化,在负高压280 V,灯电流65 m A,原子化高度8 mm,还原剂3%硼氢化钾溶液(含0.5%Na OH),载流4%盐酸的工作条件下,铁氰化钾–盐酸羟胺体系有明显的增感作用。样品中Ca~(2+)含量在4 g/L之内不影响铅的测定,溶解阶段通过高氯酸冒烟赶尽HF排除氟离子的干扰,并加入硫氰酸钠–邻菲罗啉消除铁和铜等离子的干扰。测定铅的线性范围为0~80 ng/L,相关系数r=0.999 6,方法检出限为0.187μg/L,测定结果的相对标准偏差为0.25%~1.40%(n=12),加标回收率为97.8%~104.5%。该方法测定结果与电感耦合等离子体原子发射光谱法测定结果相符。原子荧光光谱法快速准确,基体干扰少,灵敏度高。     

交错群A_5与二面体群D_6直积的整群环的挠单位

本文利用Luthar-Passi方法,研究了五次交错群A_5与六阶二面体群D_6直积的整群环的挠单位,得到了该群的Zassenhaus猜想成立.     

代数的张量积的同调满同态的构造

利用已知的代数的同调满同态来构造其张量积代数的同调满同态.设A,B,C,D是域k上的有限维代数,如果环同态f:A→C和g:B→D是环的同调满同态,则fg:AB→CD也是环的同调满同态.     

Determination of Chromium (VI) in Airborne Particulate Matter by Electrothermal Atomic Absorption Spectrometry

Hexavalent chromium Cr(VI) is a well-established carcinogen associated with lung, nasal, and sinus cancer. Cr(VI) threshold limit values in workroom air have been recently lowered. Consequently, the currently available analytical methods are insufficiently sensitive or high cost. In this paper, a simple, cost-effective, sensitive, and reproducible method using solid-phase extraction with electrothermal atomic absorption spectrometry for determination of hexavalent chromium in airborne samples is reported. The method validation included selectivity, linearity, accuracy, and precision. Interferences from other ions likely to be present in airborne samples, including trivalent chromium, were tested and selectivity was demonstrated. The detection and quantification limits were, respectively, as low as 0.1 and 0.4?µg?L^?1. The linearity ranged from 0.5 to 50.0?µg?L^?1, with a regression coefficients exceeding 0.998. The extraction recovery exceeded 98%. The developed method was successfully compared with a reference spectrophotometric method. The performances achieved were similar to ion chromatography and high-performance liquid chromatography approaches. The novel method was tested on airborne samples collected from the workplace. The method’s performance suggests that it may be an alternative to high-cost techniques for monitoring occupational exposure to hexavalent chromium.     

Surface analysis of ripple pattern on PS and PEN induced with ring‐shaped mask due to KrF laser treatment

The approach for ripple nanopattern construction on surface of two polymer substrates [polyethylene naphthalate (PEN) and polystyrene (PS)] exposed by a KrF pulse excimer UV laser through a contact lithographic mask with circular slit was proposed in this paper. Thin layer of gold was deposited on samples after the laser treatment. Changes in the morphology of the surface of both the shielded and exposed areas of the substrates, as well as the dimensions of the laser‐induced periodic surface structures, were determined (by atomic force microscopy, laser confocal microscopy and scanning electron microscopy), compared with observations and measurements made on samples treated directly (without a contact mask) under the same conditions. The morphology of the interface between the treated and untreated regions was also closely studied. Surface chemistry of treated samples was studied in detail by X‐ray Photoelectron Spectroscopy. The detailed study of surface chemistry of modified PEN and PS revealed a significant increase of oxygen concentration for laser treated PS and increase of carboxyl groups in case of PEN. The potential application of this research can be found in biotechnology, micro technology and several other fields. Copyright © 2016 John Wiley & Sons, Ltd.