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61.
电化学氢化物发生-原子荧光法测定环境样品中的Se(Ⅳ)和Se(Ⅵ) 总被引:1,自引:0,他引:1
设计了一种新的电化学氢化物发生装置, 用于测定不同价态的硒. 通过对传统的平板电解池的改进, 设计了全新的圆盘电解池并采用螺纹密封的方式, 极大地缩短了电解池的装配时间, 提高了电解池的使用寿命和密封性能. 结合热水浴在线还原技术, 将 Se(Ⅵ)在高浓度HCl介质中120 s内还原成Se(Ⅳ), 通过电化学氢化物发生技术生成氢化物, 成功的进行硒的在线价态分析. 对各种实验参数进行了详细的研究, Se(Ⅳ) 和Se(Ⅵ)的相对标准偏差分别为2.6% 和 3.1% (n=11);Se(Ⅳ)和总硒的检出限分别为0.32和0.27 μg/L (3σ). 相似文献
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The efficiency of the extraction of butyltin compounds from sediments and biological matter by acid leaching procedures has been evaluated on real samples using the hydride generation gas chromatography quartz furnace atomic absorption (GC AA) speciation method. The most efficient method uses cold pure acetic acid over a period of four hours. Hydride generation using sodium tetrahydroborate (NaBH4) is dependent on matrix composition and care must be taken to adapt the amount of reactant to the organic content of the sample. 相似文献
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Sture Nordholm 《Molecules (Basel, Switzerland)》2021,26(12)
Pauling introduced the concept of electronegativity of an atom which has played an important role in understanding the polarity and ionic character of bonds between atoms. We set out to define a related concept of atomic reactivity in such a way that it can be quantified and used to predict the stability of covalent bonds in molecules. Guided by the early definition of electronegativity by Mulliken in terms of first ionization energies and Pauling in terms of bond energies, we propose corresponding definitions of atomic reactivity. The main goal of clearly distinguishing the inert gas atoms as nonreactive is fulfilled by three different proposed measures of atomic reactivity. The measure likely to be found most useful is based on the bond energies in atomic hydrides, which are related to atomic reactivities by a geometric average. The origin of the atomic reactivity is found in the symmetry of the atomic environment and related conservation laws which are also the origin of the shell structure of atoms and the periodic table. The reactive atoms are characterized by degenerate or nearly degenerate (several states of the same or nearly the same energy) ground states, while the inert atoms have nondegenerate ground states and no near-degeneracies. We show how to extend the use of the Aufbau model of atomic structure to qualitatively describe atomic reactivity in terms of ground state degeneracy. The symmetry and related conservation laws of atomic electron structures produce a strain (energy increase) in the structure, which we estimate by use of the Thomas-Fermi form of DFT implemented approximately with and without the symmetry and conservation constraints. This simplified and approximate analysis indicates that the total strain energy of an atom correlates strongly with the corresponding atomic reactivity measures but antibonding mechanisms prevent full conversion of strain relaxation to bonding. 相似文献
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The rates of the hydride abstractions from the 2‐aryl‐1,3‐dimethyl‐benzimidazolines 1a – f by the benzhydrylium tetrafluoroborates 3a – e were determined photometrically by the stopped‐flow method in acetonitrile at 20 °C. The reactions follow second‐order kinetics, and the corresponding rate constants k2 obey the linear free energy relationship log k2(20 °C)= s(N+E), from which the nucleophile‐specific parameters N and s of the 2‐arylbenzimidazolines 1a – c have been derived. With nucleophilicity parameters N around 10, they are among the most reactive neutral C? H hydride donors which have so far been parameterized. The poor correlation between the rates of the hydride transfer reactions and the corresponding hydricities (ΔH0) indicates variable intrinsic barriers. 相似文献
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离子色谱-双阳极电化学氢化物发生-原子荧光光谱法测定Ⅰ型牙髓失活材料中的砷形态 总被引:3,自引:1,他引:2
将自制的双阳极电化学氢化物发生器作为离子色谱与原子荧光光谱的联用接口,建立了离子色谱-双阳极电化学氢化物发生-原子荧光光谱法在线分析砷形态系统.最佳实验条件为淋洗液6.0 mmol/L NH4H2PO4(pH 6.20),电解液0.40 mol/L H2SO4,电解液流量为阳极4.0 mL/min,阴极 1.5 mL/min,电解电流密度0.50 A/cm.2,载气流量300 mL/min,屏蔽气流量500 mL/min,氢气流量80 mL/min.在优化的实验条件下,As(Ⅲ)、DMA、MMA的线性范围为5~200 μg/L、As(Ⅴ)的线性范围为10~200 μg/L,As(Ⅲ)、DMA、MMA和As(Ⅴ)检出限分别为3.04、4.27、3.97和9.30 μg/L(信噪比S/N=3).50 μg/L的As(Ⅲ)、DMA、MMA和As(Ⅴ)混合标准溶液平行进样7次,得到的色谱峰面积的相对标准偏差(RSD)分别为415%、3.08%、519%和3.62%.将该方法用于牙髓失活材料中的砷形态分析. 相似文献