Baker''''s yeast mediated reduction of substituted acenaphthenequinones: Regio-and enantioselective preparation of mono-hydroxyacenaphthenones

Baker's yeast mediated reduction of acenaphthenequinone within 4-10 h afforded mono-hydroxyacenaphthenone mainly with low enantioselectivity, the substrate and mono-hydroxyacenaphthenone product almost converted to dihydroxyacenaphthene after 48 h. By control of the reaction time and in the presence of DMF as co-solvent, the reduction of 6-substituted acenaphthenequinones under vigorous agitation afforded the corresponding 2-hydroxyacenaphthenones in 24-84% yields with 10-93% ee.     

Simultaneous speciation of mercury and butyltin compounds in natural waters and snow by propylation and species-specific isotope dilution mass spectrometry analysis

A robust method has been developed for simultaneous determination of mercury and butyltin compounds in aqueous samples. This method is capable of providing accurate results for analyte concentrations in the picogram per liter to nanogram per liter range. The simultaneous determination of the mercury and tin compounds is achieved by species-specific isotope dilution, derivatization, and gas chromatography–inductively coupled plasma mass spectrometer (GC–ICP–MS). In derivatization by ethylation and propylation, reaction conditions such as pH and the effect of chloride were carefully studied. Ethylation was found to be more sensitive to matrix effects, especially for mercury compounds. Propylation was thus the preferred derivatization method for simultaneous determination of organomercury and organotin compounds in environmental samples. The analytical method is highly accurate and precise, with RSD values of 1 and 3% for analyte concentrations in the picogram per liter to nanogram per liter range. By use of cleaning procedures and SIDMS blank measurements, detection limits in the range 10–60 pg L^–1 were achieved; these are suitable for determination of background levels of these contaminants in environmental samples. This was demonstrated by using the method for analysis of real snow and seawater samples. This work illustrates the great advantage of species-specific isotope dilution for the validation of an analytical speciation method—the possibility of overcoming species transformations and non-quantitative recovery. Analysis time is saved by use of the simultaneous method, because of the use of a single sample-preparation procedure and one analysis.     

Ion Transfer in CdF<Subscript>2</Subscript>-based Iso- and Polyvalent Solid Solutions

The ionic conductivity of solid solution Cd_0.77Sr_0.23F₂ is 1.6 × 10⁻⁴ S/cm at 500 K. The conduction mechanism changes from a vacancy mechanism to an interstitial one at 523–553 K. In solid solutions Cd_0.9R_0.1F_2.1 (R = La-Lu, Y), the activation enthalpy of conduction decreases from 0.9 to 0.8 eV with decreasing ionic radius of R³⁺, raising the 500-K conductivity from 6 ×10⁻⁶ S/cm for La³⁺to 6 × 10⁻⁵ S/cm for Lu³⁺. For crystalline Cd_0.95In_0.05F_2.05, ionic and electronic conductivities at 313 K equal 5 × 10⁻⁴ and 5 − 10⁻⁶ S/cm.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 627–632.Original Russian Text Copyright © 2005 by Sorokin, Buchinskaya, Sul’yanova, Sobolev.     

Electroreduction of α-glucose on CNT/graphite electrode modified by Zn and Zn–Fe alloy

Electroreduction of -glucose to form sorbitol on Zn/CNTs and Zn alloy/CNTs electrodes has been investigated in this paper. Carbon nanotubes (CNTs) used in this paper are grown directly on graphite disks by chemical vapor deposition. Zn and Zn alloy are electrodeposited on the activated CNTs/graphite electrode by pulse galvanostatic method. The micrographs of Zn/CNTs and Zn alloy/CNTs electrodes are characterized by scanning electron microscopy. The results show that the current efficiency of -glucose reduction on CNTs electrodes is much better than that on flat Zn electrodes. The order of the current efficiency on different electrodes is as follows: Zn/CNT (0.58) Zn–Fe/CNT (0.57)>Zn–Ni/CNT (0.43) Zn/graphite (0.42)>Zn (0.40). It indicates that CNTs have good potential application in electrosynthesis. Additionally, effects of some operating parameters, such as pH, temperature and -glucose concentration, on the current efficiency of -glucose reduction are also discussed.     

Single-molecule fluorescence detection in microfluidic channels—the Holy Grail in μTAS?

Both single-molecule detection (SMD) methods and miniaturization technologies have developed very rapidly over the last ten years. By merging these two techniques, it may be possible to achieve the optimal requirements for the analysis and manipulation of samples on a single molecule scale. While miniaturized structures and channels provide the interface required to handle small particles and molecules, SMD permits the discovery, localization, counting and identification of compounds. Widespread applications, across various bioscience/analytical science fields, such as DNA-analysis, cytometry and drug screening, are envisaged. In this review, the unique benefits of single fluorescent molecule detection in microfluidic channels are presented. Recent and possible future applications are discussed.Dedicated to the memory of Wilhelm Fresenius     

Capillary electrophoresis with end-column amperometric detection of urinary 8-hydroxy-2'-deoxyguanosine

Urinary 8-hydroxy-2'-deoxyguanosine (8OHdG) is an excellent marker of oxidative DNA damage. Until now, urinary 8OHdG has been measured by high-performance liquid chromatography with electrochemical detection. A simple and sensitive method for the analysis of urinary 8OHdG by capillary electrophoresis with end-column amperometric detection has been developed in our laboratory. A single-step solid-phase extraction procedure was optimized and used for extracting 8OHdG from human urine. To improve the sensitivity of this method, a new focusing technique based on a dynamic pH junction was used. The limit of detection was 20 nM (signal-to-noise ratio S/N = 3), the linear range was 50 nM-10 microM, and the correlation coefficient was better than 0.999. The relative standard deviation (RSD) was found to be 0.57% for migration time, and 4.79% for peak current. To show the usefulness of the method, the urinary concentration of 8OHdG in nine healthy persons and ten cancer patients was determined. The urinary concentration of 8OHdG in cancer patients was significantly higher than that in healthy persons.     

Preconcentration and separation of iron, zinc, cadmium and mercury, from waste water using Nile blue a grafted polyurethane foam

The present work describes a novel method for the incorporation of Nile blue A into polyurethane foam matrix. This foam material was found to be very suitable for the extraction of metal ions from aqueous solutions. The characterization of Nile blue A grafted foam and the effect of halide concentration, pH, shaking time, extraction isotherm and capacity have been investigated. This foam material was found to be suitable for the separation and preconcentration of iron (III), zinc (II), cadmium (II) and mercury (II) from waste water. The extraction was accomplished in (15-20) minutes. Iron was separated from acid medium (2-4 M HCl), zinc from (3-5 M HCl), cadmium from (4-6 M HCl) as thiocyanate complexes and mercury was separated from (1-2 M HCl) as chloride.     

Quantitative analysis of perchlorate in extracts of whole fish homogenates by ion chromatography: comparison of suppressed conductivity detection and electrospray ionization mass spectrometry

The perchlorate anion (ClO ₄ ^– ) is an anthropogenic contaminant of increasing concern in water supplies, and has been shown to disrupt thyroid activity. Most perchlorate analyses are currently carried out by ion chromatography (IC) with suppressed conductivity detection (SCD). While this procedure has been demonstrated to provide acceptable performance for analysis of water samples, the determination of perchlorate in high-conductivity aqueous extracts of plant or animal material is not readily accomplished by IC-SCD unless lengthy cleanup protocols are applied. With the addition of electrospray ionization mass spectrometry (ESI-MS) to IC, it was hypothesized that the interference imposed by various ionic species could be significantly reduced without the need for purification; however, the analysis of perchlorate in relatively unpurified extracts of biologically derived homogenates by IC-ESI-MS has not previously been described in the literature. The research presented here represents a comparison of the capabilities of IC-SCD and IC-ESI-MS to detect perchlorate in reagent water and in crude extracts of perchlorate-exposed fish (threespine stickleback, Gasterosteus aculeatus). ESI-MS was found to compare favorably to SCD for the detection of perchlorate in deionized water, and to exceed SCD performance in perchlorate analysis of fish-derived extracts.     

聚烯烃（聚乙烯）低温热氧化与降解

综述了近年来聚烯烃特别是聚乙烯的低温热氧化机理，动力学以及氧化降解研究现状及发展，指出现今低温热氧化与降解研究意义。     

Some Reactions of 5-(3 or 4-Pyridyl)-1,3,4-Oxadiazoles with Amines and Hydrazines

2-Amino-and 2-hydrazino-5-(3 or 4-pyridyl)-1, 3, 4-oxadiazoles [II_i-k] have been prepared by racting 2-chloro derivatives with the corresponding amines or hydrazines, the 2-hydrazino (II_i-k) compounds that obtained were heated with carbon disulphide and alcoholic potassium hydroxide where 5-(3 or 4-pyridyl)-1,3,4-oxadiazolo (2,3-C)-1,2,4-triazole 5-thione (III_a-c) were obtained, the given structures were biologically screened.