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991.
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993.
Deschamps M Roiland C Bureau B Yang G Le Pollès L Massiot D 《Solid state nuclear magnetic resonance》2011,40(2):72-77
77Se (I=1/2) solid-state NMR is a very sensitive probe of the local structure of selenide glasses, which themselves are promising for optical applications. In this work, we show that although 77Se has a low natural abundance (7.58%) and a wide spectral range, the sensitivity can be dramatically increased using Carr–Purcell–Meiboom–Gill (CPMG) trains of rotor-synchronized π pulses during the detection of 77Se magnetization but may be affected by chemical shift anisotropy when the Magic Angle Spinning rate is not fast enough and by offset effects. The indirect dimension of the T2CPMG-resolved spectrum shows a strong influence of the J-couplings between naturally occurring 77Se pairs. The resulting spectra show that the structural model known as “chains crossing model” is not entirely suitable to describe the glassy network of the Se-rich compositions. 相似文献
994.
995.
ICP-MS测定食用菌中硒的方法研究 总被引:10,自引:5,他引:10
采用石英高压消化罐在较低温度下缓慢消化食用菌样品,减少了硒的损失,以ICP-MS测定食用菌中微量硒,并对分析方法进行了研究。实验表明样品浓度、积分时间与响应值呈正相关。当样品中硒的浓度大于50 μg·L-1时,采用0.1 s的积分时间;硒的浓度小于5 μg·L-1时,采用高于2.0 s的积分时间。标准曲线在1.0~500 μg·L-1完成(r=1.000 0)。回收率为99.96%~102.7%。该法具有简便、快速、灵敏、稳定、准确等优点,用于食用菌中痕量硒的分析测定,结果令人满意。 相似文献
996.
石墨炉原子吸收法测定麦芽粉中的锗和硒 总被引:11,自引:0,他引:11
本文叙述了平台石墨炉原子吸收法测定麦芽粉中的锗和硒,采用Pd+Ni和Pd基体改进剂,使锗和硒的灰化温度分别提高到1400和1200℃,有效地消除了基体干扰。方法特征量为31pg(Ge)和23pg(Se),检出限为28pgGe和62pgSe(3σ)。对含22 ̄110μg/gGe和18 ̄35μg/gSe的样品测定,相对标准偏差为Ge3.7 ̄5.6%(n=9),Se4.3 ̄6.5%(n=9),回收率在9 相似文献
997.
A simple, sensitive and interference-free method was established for simultaneous determination of trace selenium and tellurium in ore samples by HG-AFS, by using nano-TiO2-immobilized on a silica gel packed microcolumn for online preconcentration. Selenium and tellurium were selectively adsorbed to the microcolumn in acidic condition and then completely eluted with 2% (m/v) NaOH solution. The experimental conditions for hydride generation, adsorption, elution and potential interference were investigated in detail. Under the optimum conditions, the detection limits of selenium and tellurium by the proposed method with 180 s sampling time were 4.0 and 3.6 ng.L-1, with sensitivity enhancement of 20- and 13-fold compared to conventional hydride generation method, respectively. The relative standard deviation (RSD, n=5) of this method for 1 mu g.L-1 Se(IV) and Te(IV) were 0.7% and 2.3, respectively. This method was applied to determination of selenium and tellurium in several ore samples. 相似文献
998.
硒对钝顶螺旋藻氧化损伤的拮抗作用的光谱学特性及机制 总被引:2,自引:0,他引:2
研究了亚硒酸钠预处理对H2O2氧化胁迫下钝顶螺旋藻(Spirulina platensis)的生长、藻丝体形态、谱学特性以及细胞内活性氧(ROS)水平的影响,探究硒拮抗氧化胁迫保护螺旋藻的机制。结果显示,H2O2氧化胁迫明显抑制螺旋藻的生长,藻丝体严重受损,可见光吸收440nm峰增强,620和680nm峰降低;荧光发射和激发光谱特征峰强度明显降低,藻胆蛋白特征发射峰由660nm蓝移至650nm;红外光谱透射峰没有发生位移,蛋白质和多肽的特征谱带酰胺Ⅰ带和酰胺Ⅱ带相对强度降低;细胞内ROS相对含量显著性升高。硒预处理24h呈剂量效应地减轻由H2O2胁迫引起的氧化损伤,有效地抑制胞内ROS的过度累积,提高螺旋藻的抗氧化能力,缓解了氧化胁迫对光能捕获和传递等重要生理功能的影响。 相似文献
999.
流动注射氢化物发生原子吸收法测定血液中硒 总被引:2,自引:0,他引:2
采用流动注射分析与氢化物发生原子吸收相结合的方法测定了血液中痕量硒。采用HNO3-HClO4体系溶解样品,取样量少,样品处理简单,快速。本法检出限为0.06μg/L^-1(3σ),进样频率为120-150样次/小时。讨论了砷对硒测定时的干扰及其排除方法,用该法测定了300个正常人全血和75个血清样品,其硒含量范围分别为0.056-0.118μgm1^-1和0.040-0.076μgm1^-1,回收 相似文献
1000.
《Particuology》2023
Selenium pollution by coal utilization is of increasing concern. Calcium-iron (Ca–Fe) oxygen carriers (OCs) and alkali metal ions have strong inhibitory effects on selenium, which can reduce the emissions of selenium vapor. The retention mechanisms of selenium by Fe2O3, CaFe2O4, Ca2Fe2O5 and bottom ash are investigated during chemical looping gasification (CLG). Iron-based OC can oxidize H2Se(g) to SeO2(g); furthermore, lattice oxygen is released by Fe2O3, contributing to the formation of an Fe–O–Se structure to retain selenium and form selenite. Because calcium ferrite is poorly oxidizing, it cannot oxidize H2Se(g), but the CaO produced when OCs are reduced can react with H2Se(g) to form CaSe(s), and this process can be promoted by H2S(g). The best retention rates reached 32.301% when Ca2Fe2O5 was used. In the cyclic experiment, the selenium retention of the bottom ash gradually increases. Alkali metal ions in bottom ash are the main factor in retaining selenium. Ca2+ and Mg2+ do not easily vaporize due to their high melting points; therefore, their selenium retention is significantly better than that of K+ and Na+. This research provided a new idea for the removal of selenium by using OCs and bottom ash particles during CLG. 相似文献