共查询到20条相似文献,搜索用时 156 毫秒
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基于美国环境保护局(U.S.Environmental Protection Agency,USEPA)1631方法,自制双柱热脱附装置,以国产AF-610B型原子荧光仪为检测器,搭建吹扫-金柱捕集-(双柱)热脱附-冷原子荧光系统,用于测定环境样品中的总汞。对吹扫流速、吹扫时间和尾吹流速等实验参数进行了优化。双柱热脱附装置的脱附效率为99%—100%。在最优测定条件下,仪器检出限为5.0pg,海水测定的方法检出限为0.50ng/L,土壤、沉积物和红树样等固体样品测定的方法检出限为1.0ng/g。采用基底加标回收率法和参考样,验证了该系统的准确可靠性。结果表明,海水、土壤、沉积物和红树植物组织等样品的基底加标回收率均符合USEPA的限定范围,土壤参考样(ESS-4)和近海海洋沉积物参考样(GBW07314)的测定结果在参考值的可控范围内。该系统可满足环境样品中总汞测定的要求。 相似文献
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吹扫捕集与气相色谱-质谱联用测定水体中的芳烃化合物 总被引:5,自引:0,他引:5
利用吹扫捕集-气相色谱-质谱联用技术,对化工厂附近有可能受污染的地表水进行了定性和定量分析。同时对吹扫捕集的试验条件进行了优化,得到了满意的结果。 相似文献
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原子捕集-火焰原子吸收光谱法测定中草药中痕量镉 总被引:11,自引:0,他引:11
考察了火焰条件、捕集管与燃烧器和光束的距离、冷却水流量、捕集时间等实验条件对原子捕集 火焰原子吸收光谱法测定镉的灵敏度的影响 ,实验优选出的最佳实验条件为 :乙炔流量 90L·h- 1 ,捕集管距离燃烧器缝口 5mm ,捕集管距离光束 2mm ,冷却水流量 1 5L·min- 1 ;采用 5 0ng·mL- 1 的镉标准溶液对吸光度与捕集时间的关系进行了考察 ,结果发现 ,在 0~ 6min的捕集时间内二者呈良好的线性关系。在最佳实验条件下 ,捕集时间为 2min时 ,镉的特征浓度为 1 8ng·mL- 1 ,检出限为 0 4 2ng·mL- 1 ,分别较常规火焰原子吸收光谱法的特征浓度和检出限改善了 16倍和 5倍 ,方法的精密度 (RSD)为 1 8%。利用所建立的原子捕集 火焰原子吸收光谱法 ,在最佳实验条件下 ,对人参、丹参、苦参和党参及其水煎液中的痕量镉进行了测定 ,样品的测定回收率在 89 5 %~ 10 4 %之间 ,结果令人满意。 相似文献
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采用石英缝管原子捕集技术,可实现原子高效捕集和瞬间释放,使火焰原子吸收法测定铅的灵敏度比常规FAAS测定铅的灵敏度提高三至四倍。精密度与火焰原子吸收法相同。通过实验,建立了石英缝管原子捕集-火焰原子吸收光谱法测定化探样品中铅的分析方法,方法的检出限(CL)可达3.82μg/g,精密度(RSD)可达1.72%,应用于化探样品中铅的测定效果令人满意。 相似文献
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微波消解-ICP-AES法测定铁矿中P和S 总被引:1,自引:0,他引:1
采用微波加热 ,在高温高压下酸消解样品 ,应用电感耦合等离子体原子发射光谱法 (ICP- AES)同时测定铁矿中杂质元素 P和 S。选用紫外区谱线 P178.2 2 1nm、S180 .6 6 9nm,避免了基体中大量存在的 Fe、Si、Al、Cu、Mn、Ca等元素的光谱干扰。通过用纯氮吹扫光谱仪光路的方法消减空气中氧对紫外线的吸收 ,获得了足够的灵敏度。该方法简便、快速、稳定可靠 ,P、S检出限分别为 0 .0 6 7、0 .0 78μg· m L-1,回收率为89.6 %— 10 0 .7% ,RSD为 1.35 %— 5 .0 5 % ,线性范围为 0 .1— 2 0 0 μg·m L-1。 相似文献
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The lowest absorption band of the tetraphenyl compounds resembles that of the lowest absorption band of benzene with the following difference. In benzene the electronic origin is strictly forbidden, and all intensity is associated with a symmetric progression built on one mode of asymmetric vibration. In the tetraphenyl compounds the intensity associated with the asymmetric vibration is relatively unaffected; however, there is increasing intensity associated with the electronic origin and a symmetric progression built on it along the series . For the cations it is the electronic origin and the progression built on it that are the primary source of intensity. This effect is attributed to an inductive perturbation. A similar effect is observed in the fluorescence spectrum. In phosphorescence, the relative enhancement of the electronic origin and the progression built on it is far less marked. The phosphorescence emission of φ4Pb and φ4Sb+ are red shifted from the others by ~0.5 eV, an effect attributed to formation of a triplet excimer. Increasing spin-orbit coupling in the triplet due to a heavy atom effect can be seen in the decreasing phosphorescence lifetime (range 4 sec to 4 msec) and decreasing ratio of (fluorescence to phosphorescence quantum yields) in the order In all cases nonexponential decay of phosphorescence is observed. 相似文献
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The Einstein–Podolsky–Rosen paradox (1935) is reexamined in the light of Shannons information theory (1984). The EPR argument did not take into account that the observers information was localized, like any other physical object.Dedicated to the memory of James T. Cushing 相似文献
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Michael E. Fisher 《Journal of statistical physics》1984,34(5-6):667-729
New results concerning the statistics of, in particular,p random walkers on a line whose paths do not cross are reported, extended, and interpreted. A general mechanism yielding phase transitions in one-dimensional or linear systems is recalled and applied to various wetting and melting phenomena in (d=2)-dimensional systems, including fluid films and p×1 commensurate adsorbed phases, in which interfaces and domain walls can be modelled by noncrossing walks. The heuristic concept of an effective force between a walk and a rigid wall, and hence between interfaces and walls and between interfaces, is expounded and applied to wetting in an external field, to the behavior of the two-point correlations of a two-dimensional Ising model belowT
c and in a field, and to the character of commensurate-incommensurate transitions ford=2 (recapturing recent results by various workers). Applications of random walk ideas to three-dimensional problems are illustrated in connection with melting in a lipid membrane model.Based on the Boltzmann Medalist address presented at the 15th IUPAP International Conference on Thermodynamics and Statistical Mechanics, Edinburgh, July 1983. 相似文献
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M. K. Sachs M. R. Yoder D. L. Turcotte J. B. Rundle B. D. Malamud 《The European physical journal. Special topics》2012,205(1):167-182
Extreme events that change global society have been characterized as black swans. The frequency-size distributions of many
natural phenomena are often well approximated by power-law (fractal) distributions. An important question is whether the probability
of extreme events can be estimated by extrapolating the power-law distributions. Events that exceed these extrapolations have
been characterized as dragon-kings. In this paper we consider extreme events for earthquakes, volcanic eruptions, wildfires,
landslides and floods. We also consider the extreme event behavior of three models that exhibit self-organized criticality
(SOC): the slider-block, forest-fire, and sand-pile models. Since extrapolations using power-laws are widely used in probabilistic
hazard assessment, the occurrence of dragon-king events have important practical implications. 相似文献
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F. E. Close 《Contemporary Physics》2013,54(2):67-78
A particle about 50% more massive than a proton, with positive charge, positive strangeness and positive baryon number, has been claimed in several experiments. Such a particle cannot be made from three quarks; its minimal configuration requires four quarks and an antiquark and it became known as a ‘pentaquark’. This article summarizes the evidence and concentrates on the theoretical interest that it has excited into the nature of correlations among quarks and antiquarks in the strong interaction limit of QCD. 相似文献
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Salomon S. Mizrahi 《Journal of Russian Laser Research》2011,32(4):301-310
The formal structure of quantum information theory is based on the well-founded concepts and postulates of quantum mechanics. In the present contribution, I am inverting the usual approach presented in textbooks by beginning with the use of bit states as basic and fundamental units of information and establish a dynamical map for them. The condition of reversibility, imposed on an ordered sequence of actions operating on a bit state, introduces, by necessity, the unitarity property of actions. I also verify that the uniformity of time, as a parameter for ordering events, is due to the admission of a composition law for the actions. In the limit of infinitesimal intervals between actions, a reversible and linear equation arises for the dynamical changes in time of a qubit (superposition of bit states). The admission that a bit of information is stored or carried by a massive particle necessarily leads to the Schrödinger–Pauli equation (SPE); the bit is associated to a spin 1/2. Within this approach, I verify that the particle dynamical equation becomes “enslaved” by the spin dynamics. In other words, the bit (or spin) precedes in status the particle dynamical evolution, being at the root of the quantum character of the standard Schr¨odinger equation, even when spin and spatial degrees of freedom are uncoupled. 相似文献