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161.
This work presents a method to separate polar naphthalenesulfonate (NS) isomers by capillary zone electrophoresis (CZE) with ultraviolet detection in industrial effluents and river water samples. The method involves extraction of samples by a polystyrene‐divinylbenzene copolymer (PS‐DVB) solid‐phase extraction (SPE) cartridge. The most effective CZE separation conditions were obtained in 20 mM borate buffer with 30% acetonitrile at pH 9.0 and 30 °C. The method proposed herein provides a high precision and sensitivity for NS isomers, to quantitation at ≤ 1.0 μg/L in 200 mL of the water samples. Recovery of the NS isomers in spiked water samples ranged from 73% to 87% while RSD ranging from 5.6 to 9.7%. The analysis of industrial effluents and river water samples was performed and naphthalene‐2‐sulfonate was found as a major pollutant. The difficulties in quantitating and identifying analytes in complex environmental samples can be resolved by using an internal standard response factor to calculate concentrations and relative migration times for peak confirmation. 相似文献
162.
163.
以实验技术人员的视角,从不同实验环节出发,全面总结实验辅助工作,并提炼为实验辅助大三部曲和小三部曲。该方面的工作体系源于实验室开设的"化学生物学综合实验",反哺了实验室多门实验课程,取得了良好的效果,促进了实验教学质量的提升,同时也为环境育人创造了有利的条件。 相似文献
164.
Margaret Sequeira Dermot Diamond Antoine Daridon Jan Lichtenberg Sabeth Verpoorte N. F. de Rooij 《Trends in analytical chemistry : TRAC》2002,21(12):816-827
Progress in the development of a micro-fluidic system for colorimetric monitoring of ammonia in drinking and wastewater is described. The ultimate goal is to have a miniaturised instrument that can produce accurate, reliable measurements, is easy to operate, has minimal power consumption, and can operate autonomously for a year. In this study, the indophenol reaction is incorporated into a simple, reliable analytical micro-fluidic system. Absorbance measurements for the blue ammonia-indophenol complex formed in the micro-fluidic system are shown. A key issue is the limiting stability of hypochlorite, a reagent used in the assay. The effects of hypochlorite concentration and impurities on the stability of hypochlorite are investigated and discussed. Decomposition is shown to be very dependent on the presence of heavy-metal impurities. With low levels of these catalytic metals and careful storage, hypochlorite has been shown to be stable for over a year. 相似文献
165.
《Analytica chimica acta》2002,460(1):111-122
Direct cold vapour generation from aqueous slurries of environmental (marine sediment, soil, coal) and biological (human hair, seafood) samples have been developed using a batch mode generation system coupled with electrothermal atomic absorption spectroscopy. The effects of several variables affecting the cold vapour generation efficiency from solid particles (hydrochloric acid and sodium tetrahydroborate concentrations, argon flow rate, acid solution volume and mean particle size) have been evaluated using a Plackett-Burman experimental design. In addition, variables affecting cold vapour trapping and atomisation efficiency on Ir-treated graphite tubes (trapping and atomisation temperatures and trapping time) have been also investigated. Atomisation and trapping temperatures, trapping time and hydrochloric acid concentration were the significant variables. The 22+star and 23+star central composite designs have been used to obtain optimum values of the variables selected. The accuracy of methods have been verified by using several certified reference materials (PACS-1, GBW-07410, NIST-1632c, CRM-397 and DORM-2). A characteristic mass of 390 pg were achieved. The detection limits of methods were in the range of 40-600 ng g−1. A particle size less than 50 μm is adequate to obtain total cold vapour generation of Hg content in the aqueous slurry particles. 相似文献
166.
167.
Determination of dissolved organic nitrogen in natural waters using high-temperature catalytic oxidation 总被引:5,自引:0,他引:5
El-Sayed A. Eric P. Alan D. Steve J. Charlotte B. 《Trends in analytical chemistry : TRAC》2003,22(11):819-827
Studies on nitrogen in natural waters have generally focussed on dissolved inorganic nitrogen (DIN), primarily because of relative ease of analysis and the important influence of DIN on water quality. Advances in analytical techniques now permit the systematic study of dissolved organic nitrogen (DON), and this work has shown that DON is quantitatively significant in many waters. This article describes the sampling and analytical protocols required for rapid, precise and reliable determinations of DON, involving high-temperature catalytic oxidation (HTCO), coupled to chemiluminescence detection. This approach simultaneously determines dissolved organic carbon (DOC) and total dissolved nitrogen (TDN), and DON is derived by subtraction of DIN measured by colorimetry. The DON determination is simple to perform, exhibits excellent precision (<1% for C and 1.5% for N) and is applicable to a wide range of natural waters. 相似文献
168.
This paper reviews derivatisation processes applied in chromatographic determination of acidic herbicides (with carboxyl and phenol groups), mainly in aqueous environmental samples. The discussion focuses on the basic derivatisation reactions used to convert herbicides to derivatives to make them analysable by gas chromatography, and possibly to reduce detection limits and/or increase extraction recovery from aqueous samples. The reactions are transesterification, esterification, silylation, alkylation, and extractive and pyrolytic alkylation. The reagents used to conduct the reactions are numerous. Diazomethane is a very efficient methylation reagent but explosive and toxic. Methyl iodide also ensures rapid and efficient methylation. Benzyl bromide can be used directly in water but derivatisation yield is low and reproducibility is poor. Butyl chloroformate and dimethyl sulfite can also be used for derivatisation in water, and acetic anhydride can be used for in-situ derivatisation of phenolic herbicides. For increasing selectivity of GC detection pentafluorobenzyl bromide (for ECD) and (2-cyanethyl)dimethyl(diethylamino)silane (for NPD) have been applied. Very characteristic ions are produced in mass spectra if silyl groups are introduced, e.g. by using bis(trimethylsilyl)trifluoroacetamide. Tetramethylammonium, trimethylphenylammonium, tetraalkylammonium, and trimethylsulfonium hydroxides and salts can by used for derivatisation at elevated temperature in the GC injection port. Extractive alkylation is relatively efficient if tetraalkylammonium salts with long chain alkyl groups are used. 相似文献
169.
北京大学化学与分子工程学院在实施基础学科拔尖学生培养计划过程中,实行动态管理制度,低年级统一培养,高年级通过制定个性化教学方案和参加科研训练的办法遴选拔尖学生,探索"扎根课堂打好基础,依托科研提高能力,着眼交流开阔眼界"的培养模式,实现"以高水平科研带动创新人才培养"的目标。在基础核心课程中设置平行的英文班和阅读讨论班以适应不同学生的需求。2016年,随着北京大学综合改革计划的推进,进一步明确了"一体化、多层次、开放式、重基础、求创新"的教学指导思想,在注重化学基础理论知识和基本实验方法培养、注重数学和物理基础知识学习的基础上,构建多样化和多模式的立体课程体系,为学生提供适合的课程学习和个性化学术发展途径。 相似文献
170.
《Comptes Rendus Chimie》2019,22(4):321-326
Desulfurization of fuel oil is of great importance for producing clean energy. In this study, we report that tetra-alkyl orthotitanates exhibited efficient catalytic performance in the oxidative desulfurization of dibenzothiophene. The sulfur content in model oil (1000 ppmw) could be reduced to less than 10 ppmw within 10 min at room temperature and ambient pressure. In addition, the formed sulfones can be easily separated from the oil phase without extraction process. This work will provide a basis for the design of novel oxidative desulfurization catalysts with high desulfurization efficiency. 相似文献