Interfacial Behavior,Structure, and Thermodynamics of Water in Oil Microemulsion Formation in Relation to the Variation of Surfactant Head Group and Cosurfactant

Interfacial behavior, structural, and thermodynamic parameters in relation to the formation of water-in-oil (w/o) microemulsion (μE) with varied surfactant head groups and cosurfactants have been evaluated through dilution technique at different temperature and [water]/[surfactant] mole ratio. Dodecyltrimethylammonium bromide (DTAB), sodium dodecylsulphate (SDS), and polyoxyethylene sorbitan monolaurate (Tween-20) were used as surfactants and n-butanol and n-pentanol were used as cosurfactants. Distribution of cosurfactants between bulk oil and the interface using fixed amount of surfactant at varied [water]/[surfactant] mole ratio and temperature has been studied to evaluate thermodynamic parameters. Associated structural parameters, such as droplet dimension and aggregation number of surfactant and cosurfactant at the droplet interface, have also been evaluated. Spontaneity of the μE formation followed the order DTAB>SDS>Tween-20 for both butanol and pentanol in the studied range of temperature. Correlations of the results in terms of the evaluated physicochemical parameters have been attempted.     

Determination of Trace Elements in Tea and Coffee by Neutron Activation Analysis

Thermal neutron activation analysis, a high-resolution Ge(Li) gamma-ray spectrometer, and an IBM 360/67 digital computer were used to determine the concentration of Na, K, Sc, Cr, Mn, Fe, Co, Cu, Zn, Se, Br, Rb, Sb, Cs, and Hg in ground coffee and tea. This nondestructive multielement technique requires neither pre- nor postirradiation chemistry and eliminates problems of reagent contamination. The method is simple, precise and sensitive to 15 elements. Interferences from fast neutron (n, p) and (n, α) reactions are small and, if necessary, corrections may be applied easily. This technique can be applied to percolated tea and coffee.     

Investigation of the solubilization of car-emitted Pt,Pd and Rh in street dust and spiked soil samples

A sequential extraction procedure (three-step), proposed by the Standards, Measurements and Testing Programme (formerly BCR) of the European Union, was applied to street dust and spiked soil samples for the determination of PGEs. Analyses were carried out using inductively coupled plasma-mass spectrometry (ICP-MS). The results indicate that up to 5% from Pt, 70% from Pd and 14% from Rh are in mobile forms in street dust. The results for the soil samples spiked with crushed catalytic converter are significantly lower indicating that PGEs are oxidised more efficiently in natural conditions. Additionally Pt and Pd bound to humic acids were investigated.     

Accurate measurement of uranium isotope ratios in soil samples using thermal ionization mass spectrometry equipped with a warp energy filter

A chemical and mass-spectrometric procedure for uranium isotopic analysis using a thermal ionisation mass spectrometer equipped with a Wide Aperture Retardation Potential energy filter has been developed and applied to uranium isotopic measurements for various soil samples. Soil samples were digested using a microwave digestor. Uranium was isolated from soil samples by the chemical separation procedure based on the use of anion-exchange resin and UTEVA extraction chromatography column. The isotope ratios were measured for two certified reference materials by using a VG Sector 54-30 thermal ionisation mass spectrometer in dynamic mode with Faraday cup and Daly ion counting system. Replicates of standard reference materials showed excellent analytical agreement with established values supporting the reliability and accuracy of the method. Precision of the ²³⁵U/²³⁸U ratio was achieved by a correction factor of 0.22% amu as a function of ion-beam intensity with sample loads of around 250?ng of U. The resulting reproducibility for standards and soil samples was better than 0.2% at two standard deviations (SD). Uranium isotopic compositions have been determined in several reference soil samples such as Buffalo river sediment, NIST 2704, river sediment SRM 4350b and ocean sediment NIST-4357 and a Chernobyl soil sample. There was a significant deviation from the natural uranium in comparison with Chernobyl soil samples.     

Elution behaviour and environmental impact of heavy metals and rare-earth elements from volcanic ashes of Mt. Oyama,Miyake Island

To obtain information on the environmental impact of materials eluted from volcanic ashes of Mt. Oyama, Miyake Island, which erupted in July 2000, the dissolution behaviours of heavy metals and rare-earth elements from the volcanic ashes were examined. The most important characteristic of the Mt. Oyama eruption is that sulphur dioxide (SO₂) gas has been continuously released, and all persons living on Miyake Island have been required to evacuate. To estimate in terms of the volcanic eruption using SO₂ gas, the ash nature in Mt. Usu, Hokkaido, was also examined and compared with that in Mt. Oyama. When rain water mixed the ashes, the water from the ashes of Mt. Oyama became acidic because of the sulphuric acid. Therefore, SO₂ gas in Mt. Oyama can accelerate the dissolution of protons and heavy metals in the ashes, whereas the rain water in Mt. Usu was not acidic and the dissolution of the heavy metals was not so evident compared with that in the case of Mt. Oyama. With this sulphuric acid, heavy metals such as As, Cd, Pb and Hg in the ashes in Mt. Oyama easily dissolved owing to the low pH. The ashes in Mt. Oyama had been released for eight years and the amount of fallen ashes was estimated to be 33 billion tons. The weights of the harmful heavy metals in the volcanic ashes, such as As, Cd, Pb and Hg, were estimated to be 3.8?×?10², 1.3?×?10³, 1.1?×?10³ and 29?kg, respectively, and these heavy metals were dissolved and diluted in seawater. Therefore, the concentration and species (chemical form) of these metals should be carefully monitored in the future. Moreover, SO₂ gas, which has a direct effect on human health and has been monitored continuously, causes other effects, such as facilitation of metal ion elution and rock aeration.     

Simultaneous determination of inorganic arsenic,antimony, selenium and tellurium by ICP-MS in environmental waters using SPE preconcentration on modified silica

This paper deals with a simplified multi-element profiling of inorganic arsenic, antimony, selenium and tellurium in the form of ⁷⁵As, ⁸²Se, ¹²¹Sb and ¹²⁵Te by ICP-MS for amounts less than 10?µg?L^?1. Internal standards such as ⁷²Ge and ²⁰⁹Bi were successfully used for the suppression of both influence of macro elements Na⁺, K⁺, Ca²⁺, Mg²⁺ or Al³⁺, and interference of limited concentrations of heavy metal ions. Modified silica sorbents Separon? SGX C18, C8, CN, NH₂, RPS and Phenyl were tested for the preconcentration of As, Sb, Se and Te (0.25–5?µg?L^?1) in the form of ion associates with cationic surfactants from 50–250?mL sample volume. 1-etoxycarbonyl-pentadecyltrimethylammonium bromide (Septonex®, 0.005?mol?L^?1) was suitable for this purpose in the presence of 4-(2-pyridylazo) resorcinol, 2-pyrrolidinecarbodithioate and 8-hydroxyquinoline-5-sulphonic acid. The quantitative retention occurred at pH 7?±?0.2 and the mixture of acetone with ethanol in ratio 1?:?1 in the presence of 0.1?mol?L^?1 HCl was used for the quantitative elution. Organic solvents and the excess of acid were removed by evaporation prior to the determination by ICP-MS. The determination of the above trace metalloids in various kinds of water with enrichment factor till 50 times on silica Separon? SGX C18 and the above reagents were compared with the standard addition method.     

Application of a new focused microwave technology with species-specific isotope dilution analysis for the quantitative extraction of organometallic contaminants in solid environmental matrices

A new self-tuning single-mode-focused microwave technology has been evaluated in this work to perform the quantitative routine extraction of organometallic species from solid matrices of environmental interest. Species-specific isotope dilution analysis has been employed to better investigate the real influence of the microwave-assisted extractions on the final results. The advantages of such methodology in comparison with other established microwave units for the routine speciation analysis of organomercury and organotin compounds are discussed (such as the capability of using disposable glass vials, a self-tuning mode to provide an accurate control of the temperature and pressure inside of the vials, and the possibility of performing automated sequence of extractions with low sample size). The results obtained in this work demonstrated that such technology provides a fast and reliable quantitative extraction of the organometallic species in a wide range of extraction conditions even when the multi-elemental (Sn and Hg) species-specific determination is carried out.     

18O同位素标记定量肽段串联体蛋白质结合同位素稀释-多反应监测质谱的蛋白质绝对定量新方法

建立了定量肽段串联体蛋白质(concatamers of Q peptides, QconCATs)结合¹⁸O同位素标记-多反应监测质谱的蛋白质绝对定量新方法。首先对QconCAT重组蛋白质进行了纯度表征,十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)表征结果表明重组蛋白质的纯度在99%以上,相对分子质量约为63.4 kDa。对QconCAT重组蛋白质酶切后的肽段混合物进行质谱分析,并经pFind和pLabel软件处理,验证了目标肽段。还考察了QconCAT重组蛋白质的酶切效率和¹⁸O标记效率,并对QconCAT蛋白质结合¹⁸O标记-同位素稀释-多反应监测质谱方法进行了评价。实验结果表明,采用该方法对腾冲嗜热厌氧菌(Thermoanaerobacter tengcongensis, TTE)中选定蛋白质的肽段进行绝对含量测定时,相对标准偏差小于20%,准确度较高,说明该方法可用于复杂生物样本中蛋白质的绝对定量。更重要的是所建方法不仅解决了细胞培养氨基酸稳定同位素标记(SILAC)技术的重标试剂价格昂贵的问题,也为定量蛋白质组学提供了一种新的方法。     

“Ghost peaks” of olmesartan medoxomil: Two solution degradation products of olmesartan medoxomil via oxidation mediated by metal ions

Two unknown solution degradants were found during the dissolution testing in 0.1-M HCl for olmesartan medoxomil (OLM) tablets. The structure of the degradants was identified and characterized by liquid chromatography–ultraviolet (LC–UV), liquid chromatography with tandem mass spectrometry (LC–MS/MS), and nuclear magnetic resonance (NMR) and demonstrated to be cyclization of tetrazole and benzene in the olmesartan (OL) and OLM structures. A series of studies including stress studies, simulation studies, and mechanism-based studies were performed to reveal the potential mechanisms that lead to the formation of the unknown degradants. The study results demonstrated that the degradation was catalyzed with radicals that originated from the metal ions leached from the inner surface of high-performance liquid chromatography (HPLC) glass vials with dissolved oxygen under acidic condition. Prerinsing the glass vials with acidic solution dissolved with EDTA can effectively avoid the generation of such oxidative impurities. The present work provides new insights into the understanding of degradation pathways of OLM, which might support the development of OLM tablets.     

电感耦合等离子体质谱(ICP-MS)法同时测定荞麦秸秆中的8种重金属元素

基于硝酸-盐酸-氢氟酸消解体系,建立了马弗炉-微波消解-电感耦合离子体质谱(ICP-MS)法同时测定荞麦秸秆中的Cr、Cu、Ag、Mn、Fe、As、Ni、Pb等重金属含量测定方法。在微波消解的过程中,分别考察5种不同组合的混合酸体系及两种消解方法对荞麦秸秆中8种重金属测试结果的影响。实验结果表明,浓硝酸-浓盐酸-氢氟酸(6∶2∶2)混酸体系和马弗炉-微波消解样品前处理优于其他方法。在优化条件下,8种重金属加标回收率为91.2%~102%,相对标准偏差(RSD,n=5)为0.22%~4.7%,检出限为0.18~9.41μg/L。方法操作简便、快速、准确,结果可靠,能同时测定荞麦秸秆中8种重金属元素。