Determination of total gaseous selenium in atmosphere by honeycomb denuder/differential pulse cathodic stripping voltammetry

A new analytical method has been developed for the determination of total gaseous selenium in the atmosphere by honeycomb denuder collection followed by differential pulse cathodic stripping voltammetry (DPCSV) measurement. Gaseous selenium was collected in a denuder coating solution containing 2% HNO(3) and 2% glycerine. The soluble product, selenious acid, was then extracted by water for DPCSV analysis. The collection efficiency for gaseous selenium was 99.1% at a flow rate of 1 l min(-1) for 3 h. Excellent linearity in DPCSV was maintained up to Se concentration of 40 ng ml(-1). This was equivalent to a working concentration of 220 ng m(-3) of selenium in the atmosphere. A precision of 1.26% RSD (n=5) for 5 ng Se was obtained, and the detection limit (3sigma) and the quantitative determination limit were estimated to be 0.96 and 3.19 ng m(-3). The average recovery of selenium in three standard samples prepared by independent digestion of NIST SRM 1648 (Urban Particulate Matter) using our analytical system was 99.0%. The total content of gaseous selenium in the atmosphere of our laboratories was 3.2-4.4 ng m(-3).     

Coprecipitative Preconcentration and Differential Pulse Cathodic Stripping Voltammetric Determination of Selenium (IV)

Abstract

A DPCSV procedure for the determination of selenium (IV) with a prior preconcentrative coprecipitation on iron (III) hydroxide has been developed. The experimental conditions for coprecipitation of selenium (IV) onto iron (III) hydroxide, viz. pH, iron (III) concentration, volume of aqueous phase and selenium concentration, were optimized. The coprecipitated selenium (IV) is dissolved in 10 ml of 0.1 M HCl and analysed using DPCSV in the presence of copper (II). Selenium concentrations as low as 10–100 ng present in 500 ml of the aqueous phase could be determined. The method is precise and has been applied to the analysis of sea water and reference material samples.     

Fourier-transform infrared spectroscopic study of the interactions of selenium species with living bacterial cells

A study of the interactions of several selenium species with living bacterial cells was carried out by Fourier-transform infrared (FT-IR) spectroscopy. Bacterial cells consisted of an Escherichia coli strain (K-12) cultivated in a growth medium based on glucose contaminated with selenium species. Equilibrium between the analyte in the solution and the extraction medium was established, and then the effects of selenium species upon the external membrane of the living bacterial cells were characterized by performing FT-IR spectroscopy of whole cells. The presence of the toxicants at various concentrations in the culture medium had an effect on the FT-IR spectra, and the concentration of the selenium species was determined directly in the biomass by FT-IR spectroscopy. The intensity ratios between several absorption lines, which varied as a function of the concentration of the selenium species, were used as the analytical signal.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

硒化聚甘露糖醛酸的合成及抗阿尔茨海默症细胞氧化与凋亡

以聚甘露糖醛酸为原料, 采用先磺化、 再硒化的方法合成了硒化聚甘露糖醛酸, 产率为54%, 产物硒含量为437.25 μg/g. 在2.5 μmol/L硒浓度下, 硒化聚甘露糖醛酸促细胞生长能力达到最适范围, 能保护细胞免受过氧化氢损伤, 显著提高阿尔茨海默症(AD)模型细胞N2a-APP695-sw中的超氧化物歧化酶和谷胱甘肽过氧化物酶的活性, 降低细胞内活性氧自由基, 增加线粒体膜电位, 抑制细胞色素C的释放, 在促进Bcl-2表达的同时抑制Bax的表达, 从而具有抑制AD细胞凋亡的功能. 硒化聚甘露糖醛酸也能抑制AD病理相关蛋白BACE1和APP的表达. 结果表明, 硒化聚甘露糖醛酸在抗AD方面具有潜在的应用前景.     

Trace elements in the atmosphere of Ankara

Atmospheric particulate material collected in Ankara was analyzed by instrumental neutron activation analysis. The results are interpreted with respect to trace element concentrations of the earth's crust. Volatile elements such as As, Sb, Zn, Br and Hg are highly enriched suggesting noncrustal origin. Enrichment factors increase with decreasing particle size.Supported in part by the Scientific and Technical Research Council (TÜBITAK) of Turkey.     

石墨消解-原子荧光光谱法测定土壤中的总硒

为准确定量土壤硒总量,提出以逆王水(1+1)-石墨消解法消解土壤,氢化物原子荧光光谱法(HG-AFS)测定土壤总硒含量的方法.其中,对消解方式、消解时间和仪器条件进行了探讨,确定最优检测条件.称取0.2 g土壤样品加入5 mL逆王水(1+1),于石墨消解仪120℃消解1.5 h,冷却至室温后用超纯水定容至25 m L,...     

Determination of very low/levels of selenium(IV) in sea water by differential-pulse cathodic stripping voltammetry after extraction of the 3,3′-diaminobenzidine piazselenol

Selenium(IV) is determined by cathodic stripping voltammetry after the formation of a piazselenol with 3,3′-diaminobenzidine. The selenium is then accumulated as HgSe on a mercury electrode by deposition at ?0.45 V. The differential-pulse cathodic stripping peak allows a detection limit of 0.01 μg l^?1. For the determination of selenium in natural waters, interferences can be avoided by extraction of the piazselenol into toluene followed by a back-extraction into 0.5 M hydrochloric acid. The accuracy of the overall procedure was checked by analyses of a standard reference material. The method was applied to the determination of selenium(IV) in sea-water samples at levels as low as 20 ng l^?1 with a concentration factor of 10 during the extraction procedure.     

Improvement of the stability of NiO–YSZ anode material for solid oxide fuel cell

Improvement of long-term stability of 40vol.%NiO–60vol.% yttria-stabilized zirconia (YSZ) anode material in reducing atmosphere and under exposure to thermal shock through the modification of vacancy concentration and pore shape has been investigated for a solid oxide fuel cell. We varied the amount of Y₂O₃ additives from 8 to 10 mol% in YSZ and the type of carbon pore former, from plated activated carbon to spherical carbon black, to improve the strength and the stability of porous NiO–YSZ anode materials. Modifications by varying the amount of Y₂O₃ additives and carbon pore former result in a highly stable anode, even upon exposure to a reducing atmosphere for 1,200 h. In particular, the strengths of the new anode materials are markedly improved at the same porosity level. Higher strengths do not degrade during a longtime durability test in a reducing atmosphere or upon thermal shock testing. The relatively smaller degradation of electrical conductivity of the new anode material is discussed in terms of the possibility of suppression of the disconnectivity of Ni phases during operation of a solid oxide fuel cell.     

Characterization of the thermal degradation and heat of combustion of Pinus halepensis needles treated with ammonium-polyphosphate-based retardants

The thermal degradation behavior of P. halepensis needles treated with two ammonium-polyphosphate-based commercial retardants was studied using thermal analysis (DTG) under nitrogen atmosphere. Moreover, for the same experimental material, the heat of combustion of the volatiles was estimated based on the difference between the heat of combustion of the fuel and the heat contribution of the charred residue left after pyrolysis. The heat of combustion of the volatiles was exponentially related to the retardant concentration of the samples. In the range of retardant concentrations from 10 to 20% w/w the mean reduction percentage of the heat of combustion of the volatiles, with respect to untreated samples, was 18%.     

Radio-release determination of mercury vapour in air using radioactive kryptonate of selenium sulfide

Radioactive kryptonate of selenium sulfide is suggested for the determination of the concentration of mercury vapour in air. Selenium sulfide was applied as a coating to paper; upon the exposure to an atmosphere containing mercury vapor, a black color of mercuric sulfide and mercuric selenide developed. The fractional decrease in the radioactivity of the paper (related to the original specific activity) was found to be proportional to the concentration of mercury vapor and time of exposure. Other factors which can be controlled were found to be affecting the determination significantly.     

磁性Co/C纳米复合材料的合成及其对水中刚果红吸附性能研究

This comprehensive experiment has successfully introduced the frontier of scientific research into undergraduate laboratory teaching. A magnetic Co/C nanocomposite was synthesized by using ZIF-67 as the precursor. Upon calcination at high temperature in inert atmosphere, ZIF-67 was degraded and carbonized to form Co/C nanocomposite. The adsorption performance of Co/C nanocomposite for Congo Red was investigated in detail. The structure and composition of the nanocomposite were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The concentration of Congo Red was determined by UV-Vis spectrophotometry. The kinetics data was fitted with the pseudo-first-order and pseudo-second-order kinetic models. The adsorption isotherms were analyzed according to Langmuir and Freundlich isotherm models. This experiment covers the synthesis of inorganic-organic hybrid material, characterization of materials, concentration determination of dyes, analysis of dynamics data and adsorption isotherms. Therefore, this experiment enables students to practice their experimental skills, increase their interest in scientific research, and broaden their professional knowledge.     

Variation of selenium concentration in toenails following long-term storage, washing and reactor irradiation

Summary Neutron activation analysis of toenails is often used to monitor body selenium in studies looking for an association between selenium deficiency and an increased cancer risk. In this study, 87 toenail samples were analyzed for Se four times, using neutron activation with 17.4-second ^77mSe, to determine the possible systematic effects of long-term storage, the washing procedure, and irradiation in a nuclear reactor. The mean Se concentration found was 0.92 mg/g, standard deviation 0.14 mg/g. The results showed that the Se concentrations are unaffected by washing and neutron irradiation, but the samples lost moisture during storage causing a 2% increase in the mean Se concentration.     

Radiation-induced grafting of styrene onto ultra-high molecular weight polyethylene powder and subsequent film fabrication for application as polymer electrolyte membranes: I. Influence of grafting conditions

Ultra-high molecular weight polyethylene (UHMWPE) powder was irradiated by gamma rays using a ⁶⁰Co source. Simultaneous and pre-irradiation grafting was performed in air and in inert atmosphere at room temperature. The monomer selected for grafting was styrene, since the styrene-grafted UHMWPE could be readily post-sulfonated to afford proton exchange membranes (PEMs). The effect of absorbed radiation dose and monomer concentration in methanol on the degree of grafting (DG) is discussed. It was found that the DG increases linearly with increase in the absorbed dose, grafting time and monomer concentration, reaching a maximum at a certain level. The order of rate dependence of grafting on monomer concentration was found to be 2.32. Furthermore, the apparent activation energy, calculated by plotting the Arrhenius curve, was 11.5 kJ/mole. Lower activation energy and high rate dependence on monomer concentration shows the facilitation of grafting onto powder substrate compared with film. The particle size of UHMWPE powder was measured before and after grafting and found to increase linearly with increase in level of grafting. FTIR-ATR analysis confirmed the styrene grafting. The grafted UHMWPE powder was then fabricated into film and post-sulfonated using chlorosulfonic acid for the purposes of evaluating the products as inexpensive PEM materials for fuel cells. The relationship of DG with degree of substitution (DS) of styrene per UHMWPE repeat unit and ion exchange capacity (IEC) is also presented.     

Chemical and mechanical stability of EPDM in a PEM fuel cell environment

Proton exchange membrane (PEM) fuel cell stack requires elastomeric gaskets in each cell to keep the reactant gases within their respective regions. Long-term durability of the fuel cell stacks depends heavily on the functionality of the elastomeric gasket material. Chemical and mechanical stability of the elastomeric material is of great concern to the overall performance of the fuel cell stacks. The degradation of a commercially available gasket material, ethylene-propylene-diene monomer (EPDM), was investigated in a simulated PEM fuel cell environment in this work. One solution and two temperatures, based on actual fuel cell operation, were used in this study. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the gasket material before and after exposure to the simulated PEM fuel cell environment over time. Atomic absorption spectrometry was used to identify the leachants in the soaking solution from the elastomeric material. Microindentation test and dynamic mechanical analysis (DMA) were conducted to assess the change of mechanical properties of the samples exposed to the environment. The atomic absorption spectrometer analysis shows that silicon and calcium were leached from the material into the soaking solution. The ATR-FTIR results indicate that the chemical changes were not apparent. The microindentation test and DMA results reveal that mechanical properties were not changed significantly.     

Selenium intake of Australian breast fed infants

A series of 20 mother-infant pairs were studied in Brisbane, Australia at 6–12 weeks post-partum. Mean breast milk selenium concentration (±SD) was 11.9±3.5 ng/g; infants' mean 24 hour selenium intakes (±SD) were 10.7±4.1 g. Mean selenium concentration in material blood was 101 (±SD 19) ng/g and in material serum 81 (±15) ng/g.     

Relationship between the cervical uterine cancer evolution and selenium concentration in urine determied by NAA

Neutron activation analysis of Se in urine reaches an optimum sensitivity (few ppb) and precision (±12%) when the traces are complexed without using a carrier by ammonium pryrrolidindithiocarbamate (APDC) at pH 1.5–2 and adsorbed on activated carbon filters. In this way the selenium traces analysis have been carried out through^77mSe in 45 urine samples on a pre-separation basis by cyclic activation ofthe carbon filters. The selenium concentration in our blanks is virtually zero, because APDC proved to be selnium free and selenium mass in 50 mg of activated carbon used as a filter is 20 times below our qualitative detection limit and 144 times below our quantitative detection limit. The samples were first of day urine from healthy and ill women suffering cervical uterine cancer, at different evolution stages: incipient, intemediate and advanced, with no treatment, and surgery, radiotherapy, chemotherapy, or a combined treatment. The results show a consistent tred to increase the selenium trace concentration during the intemediate stage, whereas it is the same than nomal for incipient cases, and it decreases to the lowest concentrations for advanced cases.     

The determination of selenium concentration in blood and tumour tissues of breast cancer patients in Syria using instrumental neutron activation analysis

The aim of this study was to investigate the relationship of selenium concentration in blood components and tumour tissues of breast cancer patients and healthy volunteers (control), in Syria, using instrumental neutron activation analysis (INAA). Red blood cells and serum selenium concentrations were determined in 50 healthy volunteers aged 25-70 years and 70 breast cancer patients aged 25-84 years. Selenium levels were also measured in malignant and adjacent normal tissues from breast cancer patients. The accuracy of the analysis was evaluated by co-analyses of international reference materials. The results showed that selenium concentration in serum and RBC was significantly lower among breast cancer patients compared to healthy volunteers (P<0.001). The results also showed that the selenium concentration was significantly higher in the cancer tissues compared to adjacent normal tissues (P<0.001). We conclude that there is a good indication for selenium deviation in blood and malignant tissue of breast cancer patients compared to that of healthy volunteers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of selenium in bread-wheat samples grown under a Se-supplementation regime in actual field conditions

Selenium is an essential micronutrient for humans and animals, yet it is deficient in at least one billion people worldwide. Plants and plant-derived products transfer the soil-uptaken selenium to humans; therefore, the cultivation of plants enriched in selenium can be an effective way to improve the selenium status on humankind. This paper focuses on determining the ability of bread wheat to accumulate selenium after supplementation. One of the methods for supplementing this element in plants is foliar application with selenium solutions. These supplemented crop of wheat samples—bread wheat; Triticum aestivum L.—were used to determine if there is an increase of selenium content in cereal grains by comparing them with cereals cultivated in 2009 and harvested in 2010 with no supplementation. The experiments were done using sodium selenate and sodium selenite at three different selenium concentrations: 4, 20 and 100 g per hectare. Total Se is assessed by cyclic neutron activation analysis (CNAA), through short irradiations on the fast pneumatic system (SIPRA) of the Portuguese Research Reactor (RPI-ITN). The short-lived nuclide ^77mSe, that features a half-lifetime of 17.5 s, was used to determine the Se content in SIPRA. The experiment was successful, since the selenium concentration increased in the cropped grains and reached values up to 35 times the non-supplemented ones.     

SrCe0.90Gd0.10O3固体电解质燃料电池性能研究

以固相反庆方法制备了SrCe0.90Gd0.10O3含质子导电的固体电解质,对以该材料为电解质的燃料电池的性能进行了研究。结果表明,电池的输出电压强裂依赖于湿度民,其原因是电池电解质具有复杂的导电机理,通过对其在燃料电池工作气氛下的阻抗谱研究,揭示了该材料导电类型随气氛变化的规律,并从机理上对此实验加以解释,根据实验结果,确定了电解质材料的最佳使用条件。     

Dietary intake of zinc and selenium in Turkey

It is known that in the Turkish soil Se and Zn concentrations are somewhatlower than in other countries. Lower zinc intake causes significant healthproblems mostly at rural areas. Six different population groups, total of55 subjects, consisting of children, people from rural areas, university studentsand staff members were selected and diet samples were collected by duplicateportion technique. Bread and flour samples were collected from six differentbakeries in Ankara. Zinc, selenium and other trace elements in these sampleswere analyzed mostly by INAA. Daily dietary zinc intake differs among differentgroups, ranging 5–13 mg Zn/day, and for all cases, it is lower thanRDA value of 15 mg Zn/day. Similarly, selenium daily intake is around 20–53µg Se/day, which is also lower than RDA value of 55–70 µgSe/day.