Determination of As(III) using developed dispersive liquid–liquid microextraction and flame atomic absorption spectrometry

The method relies on selective complexation of As(III) with a suitable chelating agent followed by dispersive liquid–liquid microextraction (DLLME) method. Flame atomic absorption spectrometry (FAAS) equipped with microsample introduction system was utilised for determination of As(III). 1-Undecanol and acetone were used as extraction solvent and disperser solvent respectively. Some effective parameters on complex formation and extraction have been optimised. Under the optimum conditions, the enrichment factor of 108 for As(III) was obtained from 9.8?mL of water samples. The calibration graph was linear in the range of 2–15?µg?L^?1 with detection limits of 0.60?µg?L^?1 for As(III). The relative standard deviation (R.S.D.) for ten replicate measurements of 5.00?µ?gL^?1 of As(III) was 6.2%. Operation simplicity and high enrichment factors are the main advantages of DLLME for the determination of As(III) without necessity for hydride generation in water samples.     

Application of the multireference equation of motion coupled cluster method,including spin–orbit coupling,to the atomic spectra of Cr,Mn, Fe and Co

The recently introduced multireference equation of motion (MR-EOM) approach is combined with a simple treatment of spin–orbit coupling, as implemented in the ORCA program. The resulting multireference equation of motion spin–orbit coupling (MR-EOM-SOC) approach is applied to the first-row transition metal atoms Cr, Mn, Fe and Co, for which experimental data are readily available. Using the MR-EOM-SOC approach, the splittings in each L-S multiplet can be accurately assessed (root mean square (RMS) errors of about 70 cm^?1). The RMS errors for J-specific excitation energies range from 414 to 783 cm^?1 and are comparable to previously reported J-averaged MR-EOM results using the ACESII program. The MR-EOM approach is highly efficient. A typical MR-EOM calculation of a full spin–orbit spectrum takes about 2 CPU hours on a single processor of a 12-core node, consisting of Intel XEON 2.93 GHz CPUs with 12.3 MB of shared cache memory.     

无机固体材料中的忆阻效应

缺陷调控是固体化学中的基本问题,也是决定材料性能的核心要素。基于缺陷调控的忆阻效应将给未来电子信息领域带来全新的变革。本文综述了无机固体材料中忆阻效应的研究进展,主要总结了忆阻效应的产生机制和忆阻材料的类型,结合原子级p-n结的相关工作,提出深入明确电场下缺陷迁移机制将是从无机固体化学角度研究忆阻效应的重要方向。     

石墨炉原子吸收法测定PU材料中的铬

采用微波消解技术进行样品前处理,建立了石墨炉原子吸收法测定PU材料中铬含量的方法。在波长429.0 nm下,利用石墨炉程序升温测定,狭缝设为0.5 nm,塞曼效应作为背景校正。标准工作曲线线性良好,相关系数r=0.9986,方法检出限为0.051μg/L,测定结果的相对标准偏差为3.78%,加标回收率为92%～120%(n=6)。该方法简便、可行,适用于PU材料中铬的测定。     

原子荧光光谱法测定化探样品中的砷和锑

对氢化物原子荧光光谱法测定化探样品中砷和锑元素的分析条件,尤其是浸提法及预还原顺序进行了考察。样品经王水和王水溶液(1+1)分别浸提后以不同顺序预还原,结果表明,王水的氧化性会降低硫脲–抗坏血酸的还原效果,预还原时降低王水浓度能提高测定结果的准确度。在优化的测定条件下,样品中砷、锑测定结果的相对标准偏差分别为0.6%,2.7%;回收率分别为95%～101%,91%～106%;检出限分别为0.020,0.026 ng/mL。改善样品处理方法后测定结果的的准确度得到提高。     

原子荧光光谱法测定白砂糖和红糖中硒含量

目的：测定白砂糖和红糖中硒含量为研制富硒糖提供科学依据。方法采用微波消解-原子荧光光谱法测定白砂糖和红糖中硒含量。结果在确定的最佳仪器条件下,原子荧光光谱法测定白砂糖和红糖中硒的检出限为0.063μg · L-1;白砂糖硒的RSD为2.28％,红糖的RSD为2.13％;白砂糖回收率为103.4％,红糖回收率为99.7％。结论该法具有方法简便、快捷、准确等优点,适用于白砂糖和红糖中硒含量测定。     

One-step synthesis of agarose coated magnetic nanoparticles and their application in the solid phase extraction of Pd(II) using a new magnetic field agitation device

A magnetic solid phase extraction method based on agarose coated magnetic nanoparticles)ACMNPs(coupled to a new magnetic field agitation (MFA) device was developed and investigated for the separation, preconcentration and determination of Pd(II) in aqueous solutions. For the first time, the formation of the nanoparticles and their encapsulation in agarose micro-flakes was conducted in a single step. For this purpose, preparation of the magnetic iron oxide nanoparticles was performed in an alkaline agarose solution. The sizes of Fe₃O₄ nanoparticles and agarose micro-flakes were 10–14 nm and 90–130 μm, respectively. The nanomagnetic agarose particles were functionalized by iminodiacetic acid and subjected to magnetic field agitation in the MFA device. The influence of different analytical parameters such as pH, ionic strength, type and volume of desorption solvent and amount of the adsorbent on the preconcentration of Pd(II) were investigated. Eight replicated analysis at the optimized conditions, resulted in a recovery of 94.1% with an RSD of 5.2% for Pd(II). The detection limit of the method (3σ) was 47 ng L⁻¹ for the analyte. The method was successfully applied to the determination of Pd(II) in natural water samples.     

DOT2: Macromolecular docking with improved biophysical models

Computational docking is a useful tool for predicting macromolecular complexes, which are often difficult to determine experimentally. Here, we present the DOT2 software suite, an updated version of the DOT intermolecular docking program. DOT2 provides straightforward, automated construction of improved biophysical models based on molecular coordinates, offering checkpoints that guide the user to include critical features. DOT has been updated to run more quickly, allow flexibility in grid size and spacing, and generate an infinitive complete list of favorable candidate configurations. Output can be filtered by experimental data and rescored by the sum of electrostatic and atomic desolvation energies. We show that this rescoring method improves the ranking of correct complexes for a wide range of macromolecular interactions and demonstrate that biologically relevant models are essential for biologically relevant results. The flexibility and versatility of DOT2 accommodate realistic models of complex biological systems, improving the likelihood of a successful docking outcome. © 2013 Wiley Periodicals, Inc.     

Comment on “Extending Hirshfeld‐I to bulk and periodic materials”

In recent years, several methods have been developed that partition the electron density among atoms using spherically symmetric atomic weights. D. E. P. Vanpoucke, P. Bultinck, and I. Van Driessche (J. Comput. Chem. 2012, doi: 10.1002/jcc.23088) recently reported a periodic implementation of the Hirshfeld‐I method that uses a combination of Becke‐style and uniform integration grids and modified atomic reference densities to compute net atomic charges in periodic materials. Herein, this method is discussed in the context of earlier periodic implementations of the Hirshfeld‐I method, the Iterated Stockholder Atoms method, and the density derived electrostatic and chemical method.