DNA微阵列原位合成中的氧化剂体系改进

DNA芯片的制备方法主要有离片合成法和在片合成法．离片合成是用点样法将DNA探针固定在基片上;在片合成是在基片表面直接原位合成寡核苷酸探针阵列．目前国外已有多种DNA芯片原位合成方法的报道,但其中仅Fordor等提出的光脱保护DNA固相原位合成技术已商品化,该方法制备成本高,     

Use of an Aqueous Micellar Medium to Improve the Spectrophotometry Determination of Cyanide Ion with 5,5′-Dithiobis(2-Nitrobenzoic Acid)

Abstract

The spectrophotometric method for the determination of cyanide, which is based on the reaction of cyanide ion with 5,5′-dithiobis(2-nitrobenzoic acid) to displace the corresponding absorbing thiol anion, has been reinvestigated using an aqueous cetyltrimethylammonium bromide micellar reaction medium. The rate of the analytical reaction is increased considerably in the presence of the cationic surfactant. Thus, the time required for the spectrophotometric determination of cyanide ion in the 0.18 – 2.80 μg/ml range using this procedure is decreased from 25 minutes to 1 – 3 minutes.     

Reaction Dynamics with Molecular Beams and Oriented Molecular Beams: A Tool for Looking Closer to Chemical Reactions and Photodissociations

Experimental studies on reaction dynamics by use of molecular beams and oriented molecular beams are reviewed in order for looking closer to chemical reactions as well as photodissociations at the molecular level. We discuss about versatility and usefulness of the electrostatic hexapole sate‐selector as a non‐destructive selector for molecular structure analysis. Some experimental evidences on novel reaction dynamics in photodissociation and stereodynamics are presented followed by concluding remarks and future perspectives for controlling chemical reactions from the point of view of green chemistry, by manipulating molecular orientation without any catalyst nor by applying any external forces like intense electromagnetic field.     

光助Fenton法降解水中间氨基苯酚的研究

采用光助Fenton氧化法处理间氨基苯酚模拟废水,考察了光强、Fenton试剂的用量、初始pH、反应时间对降解效果的影响,初步探讨了其降解动力学规律。结果表明:在不同光源下(闭光、高压汞灯照射以及较强太阳光照射),450W高压汞灯照射以及较强太阳光照射的条件均可以明显加快Fenton法催化氧化降解间氨基苯酚溶液的过程。选择1.5mL2.5g.L-1FeSO4.7H2O,1.0mL6%H2O2,初始pH=3.5,太阳光照射下降解间氨基苯酚效果较好,反应40min后降解率高达99%;降解过程符合准一级反应动力学方程。     

ACTION DU REACTIF DE LAWESSON SUR LES HYDRAZONATES ET LES HYDROXYMATES: SYNTHESE DE SULFURES DE 1,3,4,2-THIADIAZAPHOSPHOLINES ET DE SULFURES DE 1,3,5,2-OXATHIAZAPHOSPHOLINES

Abstract

The Lawesson Reagent (L.R) 1 reacts with hydrazonates 2 and hydroxymates 3 to give 1,3,4,2-thiadiazaphospholines 4 and 1,3,5,2-oxathiazaphospholines 5 derivatives. The structure of products 4 and 5 is confirmed by IR and NMR spectroscopy.     

Effect of suppressor current intensity on the determination of glyphosate and aminomethylphosphonic acid by suppressed conductivity ion chromatography

This paper presents the application of ion chromatography with electrolytic eluent generation and mobile phase suppression for the direct conductimetric detection of glyphosate and its degradation product aminomethylphosphonic acid (AMPA). The compounds were separated on a Dionex AS18 anion exchange column with a 12–40 mM KOH step gradient from 9 to 9.5 min. The effect of the suppressor current intensity on the electrostatic interaction of these amphoteric compounds with the suppressor cation exchange membranes was evaluated. A suppressor current gradient technique was proposed for the limitation of peak broadening and baseline noise, in order to improve method sensitivity and detectability. It was observed that residual sample carbonates co-eluted with AMPA when a large injection loop was installed for the low level determination of both compounds in natural waters. For this reason, glyphosate was isocratically eluted using 33 mM KOH in order to decrease analysis time within 10 min and a column clean up step using 100 mM KOH was used to ensure retention time reproducibility. The developed method was applied to the analysis of drinking and natural water and it was further successfully applied to orange samples with slight modifications. Instrumental LOD for glyphosate was 0.24 μg/L, while method LOD was 0.54 μg/L for spring waters and 0.01 mg/kg for oranges using a 1000 μL direct loop injection of the sample. Intra-day and inter-day precision (as %RSD) for water samples was 4.6% and 12% at a spiking level of 2 μg/L, and the recovery ranged from 64% to 88% depending on sample conductivity. For orange samples, the inter-day precision was 1.4% at a spiking level of 4.4 mg/kg, while overall recovery was 103%. The developed method is direct, fast, sensitive and relatively inexpensive, and could be used as an ideal fast screening tool for the monitoring of glyphosate residues in water and fruit samples.     

Photochemical Oximesulfonylation of Alkenes Using Sulfonyl-Oxime-Ethers as Bifunctional Reagents

Utilization of oxime ethers as bifunctional reagents remains unknown. Herein, we present a mechanistically distinct strategy that enables oximesulfonylation of olefins using sulfonyl-oxime-ethers as bifunctional reagents under metal-free photochemical conditions. Via concomitant C−S and C−C bond formation, the process permits incorporation of oxime and sulfonyl groups into olefins in a complete atom-economic fashion, providing rapid access to multi-functionalized β-sulfonyl oxime ethers with good yields and stereoselectivity. The method is amenable to functionalization of complex bioactive molecules and is shown to be scalable. A radical chain mechanism initiated via photochemical Hydrogen Atom Transfer (HAT) mediated N−O bond cleavage is suggested for the process, based on our results on mechanistic investigations.     

Polyvinylpolypyrrolidone-bromine complex: Mild and efficient polymeric reagent for bromination of activated aromatic compounds

Mild and efficient method for bromination of electron-rich aromatic compounds is described using polyvinylpolypyrrolidone-bromine complex（PVPP-Br₂）.The reaction proceeded smoothly with phenols and N,N-alkylated amines to afford the corresponding monobrominated product in good yields at ambient temperature.     

光谱分析中空白与检出限的讨论

空白、检出限是分析化学中两个基本概念。本文拟从痕量分析的要求出发，以理论与实验数据结合的方式对几种空白及它们对检出限的影响进行了讨论。     

A coulometric flow cell for in-line generation of reagent, titrant or standard solutions

A universal and easily ON–OFF time operated coulometric flow cell for generation of chemicals is proposed. The cell can be used for generation of reagents, titrants or standard solutions, and can be coupled to analytical equipments in combination with flow systems for generation of micro-quantity amounts of chemicals in a wide concentration range. Platinum wire electrodes and other common laboratory available materials were employed in the cell assembly. The application of the cell for analytical purposes was illustrated by employing it for generating triiodide ions as a carrier in a flow injection analysis system applied to the analysis of dipyrone in pharmaceuticals, and as a titrant in a flow-batch analysis system applied for analysis of ascorbic acid in natural orange juice samples. Preliminary studies demonstrate that such a flow cell is suitable to allow the use of unstable reagents in analytical chemistry, since they can be generated in a closed system and promptly used in subsequent reactions. In addition, it offers advantages of saving chemicals, time and specially the laborious calibrating standard solutions preparation task of routine laboratories. Taking in account its analytical performance, the proposed cell promises to be an important tool in analytical chemistry with a great competition potential as compared to the other ones proposed in the literature.