Confirmation Studies on Polychlorinated Biphenyls (PCB) From River Waters Using Mass Fragmentography

Abstract

A specific and sensitive method to confirm the presence of polychlorinated biphenyls (PCB) in river water is described. Mass fragmentography is shown to be a proper technique especially when utilizing naturally occurring stable isotopes of chlorine. Synthesized tetrachloro-, pentachloro-and hexachlo-ro biphenyls were used to focus the mass spectrometer at three selected masses so called multiple ion detection (MID).     

乌鲁木齐河山区树轮年表特征

本文介绍乌鲁木齐河山区树轮年表特征，在年轮采样布局时，除地年轮学定理外，还依据：各支流流重的大小，径流组成的成份随高度变化及垂直气候状态等条件，作为年轮采样的原则。在近１０００平平方公里内８条主要支流上，选定了９个采点，采集１９０株树，建成９个树轮年表，共含２８０个年轮指数序列，其年表分布密度在，目前，在国内还是独有的。年表含序列数量多为４７个，最少为１９个，最长年代为４５２年，最短为１９５年。年     

基于虚功原理的悬索桥隧道式锚碇边坡稳定性分析

本文基于虚功原理,结合工程地质勘察资料,在岩层层面和不利结构面组合切割下,由于锚碇工程荷载作用,研究坝陵河大桥西岸隧道式锚碇边坡的整体稳定性。本文的力学分析模型采用多个块体破坏机构的分析方法,假定块体的底面和侧面均达到了极限平衡状态,安全系数可通过功能平衡的虚功原理表达式来求解。功能平衡方程中仅有安全系数一个未知数,条块底部和界面上的法向压力和切向摩擦力并不出现,求解大为简化。     

Ultrasound‐assisted emulsification microextraction based on a solidified floating organic droplet for the rapid determination of 19 antibiotics as environmental pollutants in hospital drainage and Gomti river water

Antibiotics that are used excessively and disposed of improperly are categorized as emerging pollutants. The determination of micropollutants in water with an accurate and precise method is always a big challenge. Hence, a simple, rapid, sensitive, economical and almost eco‐friendly method is proposed for the quantitative determination of 19 antibiotics. The proposed method, ultrasound‐assisted emulsification microextraction and solidified floating organic droplet coupled with liquid chromatography and triple quadrupole mass spectrometry, has only a 3 min chromatographic run time for the determination of the 19 antibiotics. We report for the first time the use of the developed method for the quantitative determination of the antibiotics in waste water samples with better results in terms of higher sensitivity, cost‐effectiveness, better detection limits and a greener approach compared to the earlier reported methods. The limits of detection and quantification were in the range of 0.003–0.236 and 0.013–0.834 μg/L, respectively, with good linearity in the concentration range of 0.01–64.0 μg/L. The correlation coefficient was ≥0.987–0.99 for each analyte. The developed method has been successfully applied for the determination of antibiotics in water samples.     

A rapid, sensitive and effective quantitative method for simultaneous determination of cationic surfactant mixtures from river and municipal wastewater by direct combination of single-drop microextraction with AP-MALDI mass spectrometry

A rapid, simple, sensitive, and effective quantitative method for simultaneous determination of cationic surfactants (CS(+)) from river and municipal wastewater by direct combination of single-drop microextraction (SDME) with atmospheric pressure (AP)-MALDI mass spectrometry has been successfully demonstrated without the requirements of tedious sample pre- or post-treatment or separation by high-performance liquid chromatography (HPLC), gas chromatography (GC), and capillary electrophoresis (CE). This quantitative method can greatly enhance the signal-to-noise ratio for analysis of small molecules of CS(+) owing to the strong suppression of matrix ions by the analytes. In addition, SDME assisted in the isolation and preconcentration of CS(+) from water samples, which could effectively reduce the background interferences from the matrices present in waste and river water. The SDME conditions were optimized for achieving high extraction efficiency of CS(+) from aqueous samples, in terms of solvent selection, stirring speed, extraction time, exposure volume of acceptor phase, and salt addition. The enrichment factors for CS(+) were found to be 40-64-folds for 7 min of extraction time with no salt addition and at room temperature. This method was found to yield a linear calibration curve in the concentration range from 50 to 1500 microg/l CS(+) with a limit of detection (LOD) of 10 microg/l. The relative recoveries in river and municipal wastewater were found to be 93.8-103.6% and 91.0-98.7%, respectively. These results indicate that the combination of SDME with AP-MALDI/MS is effective for the simultaneous determination of CS(+) from river and municipal wastewater. In addition, a comparison of enrichments and LOD values for this method with hollow-fiber liquid phase microextraction (HF-LPME) was also demonstrated. The present approach is easy to operate, rapid, sensitive, and suitable for high-throughput of analysis.     

环江县大环江下游沿岸重金属污染区农作物污染评价

采样分析了广西环江县大环江河下游沿岸受重金属污染的4块农田土壤及农作物可食用部分重金属含量,并进行了污染评价。结果表明,4块受污染农田土壤重金属污染级别均为轻污染,受污染农田土壤上种植的油麦菜、茼蒿、生菜、小白菜、稻米等农作物可食用部分为重污染,污染水平远远超过国家食品卫生限值标准。建议在未经改良的情况下,不宜在重金属污染的土壤上种植此类农作物。     

青海湖区河谷灌丛主要植物微量元素含量特征

采集青海湖地区沙柳河河谷灌丛14种主要植物，采用AAS分析了其中7种微量元素含量。结果表明，元素Cu、Mn、Co含量有较大的植物种问差异，7种微量元素中Se含量最小，Fe含量最大。元素Mn和Fe、Co、Ni之间都具有极显著的正相关性，即相互之间具有协同性作用。     

Geometric and electronic structures of silicon fluorides (N = 4 – 6) and potential energy surfaces for dissociation reactions → SiF4 + F– and → + F–

The geometric and electronic structures of a series of silicon fluorides (n = 4 ? 6) were computationally studied with the aid of density functional theory (DFT) method with B3LYP and M06‐2X functionals and coupled cluster (CCSD and CCSD(T)) methods with 6‐311++G(d,p) basis set. The nature of the Si‐F bonds in these compounds was analyzed in the framework of the natural bond orbital theory and natural resonance theory. Energy characteristics (heats of reactions and energy barriers) of the dissociation reactions → SiF₄ + F^– and → + F^– were calculated using the DFT and CCSD methods. The potential energy surface of elimination of a fluoride anion from has a specific topology with valley‐ridge inflection points corresponding to bifurcations of the minimal energy reaction path. © 2016 Wiley Periodicals, Inc.     

Note on the theory of bifurcation of chemical reactions

In the present communication two existing definitions of valley ridge inflection, (VRI), point, one attributed to Valtazanos and Ruedenberg and the other one to Basilevsky are discussed. From our study we conclude that both definitions are not equivalent, and we demonstrate in which cases it occurs. However, they are used without any distinction in the bibliography. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Determination of Dialkyldimethylammonium Surfactants in Consumer Products and Aqueous Environmental Samples Using the Mixed Micelle-Based Methodology

Abstract

The determination of dialkyldimethylammonium surfactants (DDAS) based on the measurement of the critical micelle concentration (CMC) of mixed sodium dodecylsulphate (SDS)-DDAS aggregates in a basic medium ([NaOH]=4.8 × 10^?3 M) is proposed. The dye Coomassie Brilliant Blue G (CBBG) was used as a photometric probe for the rapid determination of CMCs. Formation of CBBG-DDAS and DDAS-SDS premicellar aggregates of well-defined stoichiometrics at cationic and anionic surfactant concentrations far below their CMCs is demonstrated. Increased SDS concentration in the titration medium results in the formation of DDAS-SDS mixed micelles. The strong interaction between the opposite charged head group of DDAS and SDS permits these cationic surfactants to be determined at the ng ml^?1 level with a nearly uniform response for all the DDAS tested (12–18 alkyl carbons). The relative standard deviation for 1.10 μg ml^?1 ditetradecyldimethylammonium bromide (DTDAB) was 1.5%. The mixed-micelle based methodology was applied to the determination of DDAS in softeners and aqueous environmental samples (river water and laundry effluents) with average recoveries ranged from 87.1 to 100.6 and from 96.3 to 104.0, respectively.