Preconcentration of trace nickel lons from aqueous solutions by using a new and low cost chelating polystyrene adsorbent

A simple and reliable method has been developed using chelating polymeric adsorbent (PSAHSB) to preconcentration of trace amount of Ni(II) ions from aqueous solutions under static loading conditions, and their determination by Ultraviolet and visible (UV–Vis) absorption spectroscopy. The influences of some analytical adsorption parameters, such as pH, temperature and contact time, the ionization constants of chelating groups in the adsorbent and desorption process were investigated. Maximum adsorption ≥98% was achieved at pH 3–7 after 20 min of contact time and the relative standard-deviation values were ≤5%. Adsorbed metal ions have been desorbed with 10 mL of 2 M HCl acid with the detection limit of 0.0157 μg m⁻¹. The Langmuir and Freundlich isotherm equations were used to describe adsorption behavior of the system at different temperatures. Kinetic and thermodynamic behavior of the adsorbent for Ni(II) ion preconcentration was also studied. The possible adsorption mechanism of Ni (II) ions onto modified adsorbent is also discussed. This method was applied efficiently to remove Ni (II) ions from environmental water samples.     

利用阿秒激光追踪和控制原子分子内部电子的运动

随着强激光技术的快速发展, 在物质与激光相互作用下,实验上发现了很多新奇的物理现象。这些现象成功地被各种理论模型和数值模拟所解释和证明。一种很重要的现象就是所谓的高次谐波产生：在原子和分子与强激光相互作用时, 能够放出能量为基频光子能量几倍到几百倍的大能量光子。在实验上, 人们已经可以通过合成截止频率附近的几个谐波来产生脉冲长度在阿秒量级的激光脉冲（1阿秒=10-18秒）。阿秒脉冲的获得开启了超快科学一个全新的领域：人们可以在电子运动的自然时间尺度上去探测和操控原子分子内部电子的运动,这是继飞秒科学后人们操控微观世界物质运动的又一大飞跃。在本文中,我们就最近几年我们在理论上所开展的阿秒物理做一个简单的综述,重点强调利用阿秒光去控制电子的电离动力学以及探测分子内部电子运动.     

Simple model for the ionization of helium atoms by fully and partially stripped ions in the strong interaction region

Theoretical calculations employing the modified over-barrier model to investigate single and double ionization cross sections of helium in collisions with highly charged ions are presented in the strong perturbation region. It shows the velocity and charge state dependences of cross sections, which coincides with the available experimental data. In order to determine the reliability of this model for partially stripped projectiles, the cross-section ratios have been measured for CZp+, OZp+-He (Zp=1-4) by the coincidence technique in the velocity range of 1-4.5 a.u. The calculated results are approximately in agreement with the experimental data.     

Classical Molecular Dynamics Model for Coupled Two‐Component Plasmas – Ionization Balance and Time Considerations

The dynamic properties of ion‐electron two‐component plasmas (TCP) are studied by using classical molecular dynamics (MD) simulations. There is a variety of time dependent and structural results that MD is able to provide in complement to other methods, e.g., useful micro‐field sequences can be generated. The method deals with some specific difficulties: the mass ratio between ions and electrons enforces very small time‐steps appropriate to follow electrons motion while, ions must move significantly in order to build, self consistently, their spatial structure. This results in expensive simulations. Electron trajectories are trapped and de‐trapped with multiple electron collisions around ions resulting in the occurrence of quasi metastable bound electron states. An analysis of micro‐fields at neutral in a hydrogen plasma reveals the need to consider a complete hierarchy of time scales extended typically over 7 order of magnitude, i.e., from a time‐step: ～10^‐19s, to a time required to obtain statistical averages, ～10^‐11s. In order to extend the MD capabilities in representing real coupled plasmas a classical ionization/recombination process has been implemented allowing to follow the evolution of plasmas involving several ion stages and model the ionization balance. Here again TCP simulations deal with extended time‐scale providing information about relaxation of non equilibrium plasma states (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multi-residue confirmatory method for the determination of twelve coccidiostats in chicken liver using liquid chromatography tandem mass spectrometry

The confirmatory LC-MS/MS method for the determination of residues for twelve coccidiostats including ionophore antibiotics (lasalocid, maduramycin, monensin, narasin, salinomycin, semduramycin) and chemical coccidiostats (clazuril, decoquinate, diclazuril, halofuginone, nicarbazin and robenidine) in poultry liver has been developed. The sample preparation was based on extraction with acetonitrile, defatting with Alumina columns and clean-up on Oasis HLB spe. The separation of analytes was performed on PhenylHexyl column with a gradient of acetonitrile, methanol and the ammonium formate pH 4.0. For all analytes, at least 2 diagnostic fragmentation ions were monitored. The validation, performed according to the CD 2002/657/EC, proved the suitability of the method for the confirmatory analysis of the coccidiostats. For lasalocid, however, low reproducibility was observed and the proper quantification could not be performed with this method.     

A DFT Study on the Selective Extraction of Metallic Ions by 12-Crown-4

In order to predict the extraction ability of 12-crown-4 for different metallic ions, the complexes [M(12-crown-4)] and [M(H₂O)₄] (where M=Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, Ca²⁺, Cu²⁺ and Zn²⁺) were investigated by the density functional theory without restrictions for their geometry. The metal binding capability was evaluated using the binding energy, and the effect of nature of the metal on the binding properties was also studied. The results of the calculations showed that the coordination ability of a donor molecule towards different metal ions increased in proportion to their ionization potential. In addition, based on the extraction distribution coefficient, we found that 12-crown-4 can selectively extract Cu²⁺ and Be²⁺ ions from aqueous solutions of mixed cations. Obviously, the stability of complexes and the extraction power of extractants depend greatly on the nature of the metal ions. Calculation results from our study could be used to predict the extraction power of this crown ether and could play a guiding role in planning experiments.     

Chemical Bonding and Electronic Structure of 4d-Metal Monosulfides

Bond distances, vibrational frequencies, dissociation energies, electron affinities, ionization potentials and dipole moments of the title molecules in neutral and charged ions were studied by use of density functional method. Ground states for each molecule were assigned. The calculated bond distance decreases with the increasing of atomic number of 4d metals, reaches minimum at RhS, then increases. For cationic molecules, the calculated bond distance decreases to the minimum at MoS⁺, then increases. The calculated vibrational frequency decreases from YS(YS⁺) to PdS(PdS⁺) for both neutral and cationic molecules. The bond ionic character decreases from YS(YS⁺) to PdS(PdS⁺) for neutral and cationic molecules. The bonding patterns are discussed and compared with the available studies. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cations of halogenated methanes: adiabatic ionization energies, potential energy surfaces, and ion fragment appearance energies

The DFT-B3LYP and G3X model chemistry were used to predict the cation structures and energetics of fluorinated, chlorinated, and brominated methanes. Ion–complex structures between methylene cations and HX (X = F, Cl, Br) were found for all H-containing cations, and [CHF–FH]⁺, [CF₂–FH]⁺, [CCl₂–ClH]⁺, and [CCl₂–FH]⁺ structures are more stable than their normal tetravalent structures. Several cations should also be better described as ion–complex structures between methyl cations and halogen atoms, e.g., [CF₃–Br]⁺. Transition states connecting normal and ion–complex structures were also located, and potential energy diagrams were constructed for decomposition of methane cations and to predict the fragmentation pathways. The G3X energies were used to predict the adiabatic ionization energies (IE_as) and ion fragment appearance energies (AEs) from methanes. Many of the experimental AEs correspond to the energies of transition states instead of the thermodynamic dissociation limits. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Alleviation of ion suppression effect in sonic spray ionization with induced alternating current voltage

In this study, alleviation of ion suppression effect in sonic spray ionization mass spectrometry (SSI‐MS) was investigated. Ion suppression effect was firstly compared between electrospray ionization (ESI) and conventional SSI, and more severe ion suppression effect was observed with SSI. Ion suppression effect of SSI was also found difficult to be alleviated by simply optimizing major parameters. Alternatively, we found that with the assistance of an alternating current (AC) voltage with low amplitude, the ion suppression effect was greatly alleviated (comparable with conventional ESI). That AC voltage was applied outside the SSI spray tip, and no direct contact between the electrode and spray solution was necessary. Besides the alleviation of the ion suppression effect, this newly‐developed method, termed as induced electrosonic spray ionization (IESSI), appeared to preserve similar charge state distribution with SSI for protonated cytochrome c, hemoglobin, and bradykinin. IESSI could also obtain significantly improved ion intensities (~1000‐fold over conventional SSI). In addition, tolerance of concentrated salts for IESSI‐MS was investigated through the analysis of cytochrome c in the presence of concentrated sodium chloride (NaCl) or ammonium acetate (NH₄OAc). Copyright © 2014 John Wiley & Sons, Ltd.     

Gradient‐based solvent suppression methods on a benchtop spectrometer

Benchtop NMR emerges as an appealing alternative to widely extend the scope of NMR spectroscopy in harsh environments and for on‐line monitoring. Obviously, the use of low‐field magnets induces a dramatic reduction of the spectral resolution leading to frequent peak overlaps. This issue is even more serious because applications such as chemical process monitoring involve the use of non‐deuterated solvents, leading to intense and broad peaks overlapping with the signals of interest. In this article, we highlight the need for efficient suppression methods compatible with flowing samples, which is not the case of the common pre‐saturation approaches. Thanks to a gradient coil included in our benchtop spectrometer, we were able to implement modern and efficient solvent suppression blocks such as WET or excitation sculpting to deliver quantitative spectra in the conditions of the on‐line monitoring. While these methods are commonly used at high field, this is the first time that they are investigated on a benchtop setting. Their analytical performance is evaluated and compared under static and on‐flow conditions. The results demonstrate the superiority of gradient‐based methods, thus highlighting the relevance of implementing this device on benchtop spectrometers. The comparison of major solvent suppression methods reveals an optimum performance for the WET‐180‐NOESY experiment, both under static and on‐flow conditions. Copyright © 2016 John Wiley & Sons, Ltd.