Determination of mercury in polluted soils surrounding a chlor-alkali plant: Direct speciation by X-ray absorption spectroscopy techniques and preliminary geochemical characterisation of the area

Soil samples collected in the surroundings of a chlor-alkali plant in the Netherlands were characterised by synchrotron-based techniques and conventional analytical procedures, in order to evaluate the environmental impact of Hg emissions and other heavy metals present in these locations. Analysis of total metal content by inductively coupled plasma-optical spectroscopy (ICP-OES) revealed a heterogeneous contamination of Hg, with concentrations ranging from 4.3 to 1150 μg g⁻¹. In addition, significant concentrations of Cu, Ni, Pb, Zn, Mn and principally Fe were also identified within the studied samples. Direct determination of mercury species by X-ray absorption near edge spectroscopy (XANES) showed inorganic Hg compounds to prevail in all soils, being Cinnabar (HgS_red) and Corderoite (Hg₃S₂Cl₂) the main species. Nevertheless, more soluble mercury compounds, such as HgO and HgSO₄, have been also identified in significant proportion (from 6 to 20% of total mercury content), indicating a potential risk of mercury mobilisation. On the other hand, the application of sequential extraction schemes (SES) revealed large portions of weakly available Hg extracted in the residual fraction, while Hg associated to the exchangeable phase amounts as much as 19% of total Hg, thus, supporting the results obtained by XANES.Finally, synchrotron-based micro X-ray fluorescence (μ-XRF) was applied to identify qualitative trends on elemental associations in sample particles through a systematic mapping of its surface. In this concern, results show a well-defined correlation between Hg and Cu/Ni in the analysed particles. On the other hand, an absence of correlation between Hg and several other elements (Fe, Ti, Ca, Zn, Mn and S) was also observed. These effects have been attributed to chemical and physical interactions of mercury species on both enriched particles and sample matrices.     

Platinum(II) complex-catalyzed enantioselective aldol reaction with ketene silyl acetals in DMF at room temperature

[{(R)-binap}Pt(μ-OH)]₂2X is a weak Lewis acid, which can catalyze the enantioselective aldol reaction of aldehydes with ketene silyl acetals in DMF at room temperature. The platinum(II) complex-catalyzed the enantioselective aldol reaction of aldehydes with 1-methoxy-2-methyl-(1-trimethylsilyloxy)propene gave the corresponding aldols in high yields with enantioselectivity up to 92%. With 5 mol % loading of the complexes, the enantioselective aldol reaction of aldehydes with 1-benzyloxy-1-(trimethylsilyloxy)propene smoothly proceeded in DMF containing 10% HMPA as to predominantly give anti-propionates with enantioselectivity up to 89%, irrespective of the silyl nucleophile geometry.     

Synthesis,crystal structure and antibacterial activity of a new binuclear copper(II) complex with N,N ′- bis ( N -hydroxyethylaminopropyl)oxamido as a bridging ligand

A new μ-oxamido-bridged dicopper(II) complex, [Cu₂(heap)](ClO₄)₂?·?2H₂O [H₂heap?=?N,N′-bis(N- hydroxyethylaminopropyl)oxamido], has been synthesized and structurally characterized by elemental analyses, molar conductance, IR and single-crystal X-ray diffraction. The single crystal X-ray analysis reveals that the asymmetric unit of the complex is composed of half a binuclear cation [Cu₂(heap)]²⁺, one perchlorate anion, and one lattice water molecule. Each copper(II) atom is tetracoordinate in a distorted square-planar geometry and the bridging ligand (H₂heap) adopts the trans conformation with an inversion centre at the middle of the C2–C2ⁱ bond. The structure cohesion is ensured by hydrogen bonding interactions, which form a two-dimensional supramolecular framework. The antibacterial assay indicates that the complex showed better activity than the ligand.     

Synthesis,crystal structure,and DNA binding of a new oxalato-bridged binuclear zinc(II) complex

A new binuclear zinc(II) complex bridged by μ-oxalate, and end-capped with 2,2′-bipyridine (bpy), [Zn₂(ox)(bpy)₄](ClO₄)₂ · H₂O, has been synthesized and characterized by elemental analyses, molar conductance, IR, and electronic spectra and single-crystal X-ray diffraction. The single-crystal X-ray analysis reveals that the [Zn₂(ox)(bpy)₄]²⁺ cation has two zinc(II) centers bridged by a planar bis(bidentate) oxalate group with Zn···Zn distance of 5.482(3) Å; each zinc(II) is in a distorted octahedral environment. The crystal structure is stabilized by non-classical C–H···O hydrogen bonds and π–π stacking interactions to form a 3-D supramolecular structure. The interaction of the complex with calf-thymus DNA (CT-DNA) was explored by using electronic and fluorescence spectra and viscosity measurements. The results reveal that the complex intercalates with CT-DNA with intrinsic binding constant of 4.1 × 10⁴ M^?1.     

A Computer Program for Identifying Anomalous Peaks in Automated Amino Acid Analyses

Abstract

In automated ion-exchange chromatography of amino acids utilizing spectrophotometric measurement., the ratio of the areas under the 40 mμ; and 570 mμ; absorption peak tracings has been shown to be specific for each amino acid. Symmetrical, but impure peaks have ratios deviating from these norms. A simple computer program for the rapid identification of these anomalous peaks has been designed. It is proposed as an addendum to any computer program now in use with amino-acid analyzers.     

An antiferromagnetically coupled hexanuclear copper(II) Schiff base complex containing phenoxo and dicyanamido bridges: Structural aspects and magnetic properties

A novel hexanuclear complex [{(CuL)₂Cu}₂(μ-dca)₂](ClO₄)₂·2L′(1) (where H₂L = (OH)C₆H₄C(CH₃)N(CH₂)₃NC(CH₃)C₆H₄(OH) or N,N′-bis(2-hydroxyacetophenone) propylenediimine and dca = N(CN)₂⁻ and L′ = 2-hydroxyacetophenone) has been synthesized and characterized by elemental analysis, UV-Vis, FT-IR spectroscopic and electrochemical methods. Single crystal X-ray structural characterization reveals a centrosymmetric nature of the complex unit, where the metal centers adopt distorted square-planar and distorted octahedral geometries. Structural analysis also reveals μ₂-phenoxo bridges between terminal and the central copper(II) centers of the asymmetric [(CuL)₂Cu(dca)] unit, the latter being interconnected to its symmetry related counterpart by double μ_1,5-dca bridges, leading to the hexanuclear complex ion [{(CuL)₂Cu}₂(μ-dca)₂]²⁺. Low temperature susceptibility measurements of 1 revealed the presence of strong antiferromagnetic coupling (2J = −407 cm⁻¹) between the copper(II) centers.     

微流蒸发光散射检测器与加压毛细管电色谱联用测定川贝枇杷糖浆中6种有效成分的含量

建立了同时测定川贝枇杷糖浆中6种有效成分(桔梗皂苷D、贝母辛、齐墩果酸、西贝素、贝母甲素和贝母乙素)含量的微流蒸发光散射检测器(μELSD)与加压毛细管电色谱(p CEC)联用检测方法。搭建p CEC-μELSD联用平台,采用C18毛细管色谱柱(EP-150-15-3-C18),流动相为乙腈(A)-10 mmol·L-1甲酸-三乙胺水溶液(p H 11.0)(B),梯度洗脱,柱流速为1.02μL·min-1,施加电压为+10 k V,雾化载气流速为0.4 L·min-1,蒸发温度为40℃。川贝枇杷糖浆中6种有效成分可在10 min内得到分离检测,6种有效成分的线性范围可达4个数量级,检出限均在pg水平,加标回收率为97.9%~103.0%。所建立的p CEC-μELSD联用方法精密度、重复性和稳定性良好,且简便、快速、可靠,可用于川贝枇杷糖浆中6种有效成分的含量测定。     

微束X射线荧光光谱仪测定射击残留物特征元素分布图的应用研究

通过优化定距射击样本采集条件,考察了六四手枪在不同距离(0,2,5,10,15,20,25,30,35,40,45,50,60,80,100,120,140,170,200,300,500,1 000 cm)垂直射击PU布块靶体时相关元素(氯、钾、硫、锑、锡、钡、铅、汞、砷、铁、铜、锌、钛、钙、铑)的区域扫描图,建立了微束X射线荧光光谱(μ-XRF)面扫描技术分析射击样本的方法,并建立了六四手枪射击残留物特征元素分布图形随射击距离而变化的数据模型,同时对所得数据进行了归一化处理。本方法可协助推断射击距离,为涉枪案件的侦查与诉讼提供科学证据。     

Dispersive micro-solid-phase extraction of benzodiazepines from biological fluids based on polyaniline/magnetic nanoparticles composite

In this study, diverse types of Fe₃O₄ nanocomposites modified by polyaniline, polypyrrole, and aniline–pyrrole copolymer were synthesized through chemical oxidative polymerization process for dispersive-μ-solid phase extraction (D-μ-SPE) in the presence of various dopants. The results showed that the nanocomposite modified by polyaniline with p-toluene sulfonic acid as a dopant demonstrated higher extraction efficiency for lorazepam (LRZ) and nitrazepam (NRZ). Also the synthesized magnetic sorbents were characterized. The nanocomposite sorbent in combination with high performance liquid chromatography–UV detection was applied for the extraction, preconcentration and determination of lorazepam and nitrazepam in urine and plasma samples. Different parameters influencing the extraction efficiency including: sample pH, amount of sorbent, sorption time, elution solvent and its volume, salt content, and elution time were optimized. The obtained optimal conditions were: sample pH, 6; amount of sorbent, 5 mg; sorption time, 5.0 min; elution solvent and its volume, 0.5 mM cethyltrimethyl ammonium bromide in acetonitrile, 150 μL; elution time, 2.0 min and without addition of NaCl. The calibration curves were linear in the concentration range of 1–2000 μg L⁻¹. The limits of detection (LODs) were achieved in the range of 0.5–1.8 μg L⁻¹ for NRZ and 0.2–2.0 μg L⁻¹ for LRZ, respectively. The percent of extraction recoveries and relative standard deviations (n = 5) were in the range of 84.0–99.0, 6.1–7.8 for NRZ and 90.0–99.0, 4.1–7.0 for LRZ, respectively. Ultimately, the applicability of the method was successfully confirmed by the extraction and determination of NRZ and LRZ in human urine and plasma samples.     

Reaction of [P3N3Cl4(NH2)2] with [HN(POCl2)2]; The crystal structure of the phosphazenium salt [P3N3HCl4(NH2)2]+[N(POCl2)2]−

The reaction of diaminotetrachloro-cyclotriphosphazene with tetrachloride of μ-imino-diphosphoric acid leads to the formation of the salt-like compound [P₃N₃HCl₄(NH₂)₂]⁺[N(POCl₂)₂]⁻ which identity was unambiguously established by means of X-ray structure analysis. The structure is composed of [P₃N₃HCl₄(NH₂)₂]⁺ cations and [N(POCl₂)₂]⁻ anions joined by a system of H-bonds. As in other phosphazenium salts, the protonation of the ring N atom leads to significant changes in the endocyclic P N bond lengths.