Elimination of SAS Interferences in Catalytic Adsorptive Stripping Voltammetric Determination of Cr(VI) by Means of Fumed Silica

In the work the procedure of chromium(VI) determination by catalytic adsorptive stripping voltammetry (CAdSV) with application of fumed silica, is presented. Two variants of the method are proposed: in the first fumed silica is put directly to the electrolytic cell containing tested solution, in the second the silica is shaken with the sample and next centrifuged. The effectiveness of many surface‐active substances removal from synthetic solutions as well as natural water samples, is studied. In the experiments the fumed silica (Sigma‐Aldrich) of the specific surface area in the range 200–390 m² g^?1 was used. Two types of the working electrodes were applied, i.e., hanging mercury drop electrode (HMDE) and cyclic renewable mercury film electrode (Hg(Ag)FE). In the silica presence i) the relative standard deviation (RSD) for 0.1 μg L^?1 Cr(VI) is <2% (HMDE) and <5% (Hg(Ag)FE), n=7, ii) the detection limits estimated deposition time 20 s were respectively 14 ng L^?1 (HMDE) and 22 ng L^?1 (Hg(Ag)FE). The accuracy of the method was tested by studying the recovery of Cr(VI) from spiked natural water samples.     

Analysis of sorption and bioavailability of different species of mercury on model soil components using XAS techniques and sensor bacteria

The present work studies the adsorption behaviour of mercury species on different soil components (montmorillonite, kaolinite and humic acid) spiked with CH₃HgCl and CH₃HgOH at different pH values, by using XAS techniques and bacterial mercury sensors in order to evaluate the availability of methyl mercury on soil components. The study details and discusses different aspects of the adsorption process, including sample preparation (with analysis of adsorbed methyl mercury by ICP-OES), the various adsorption conditions, and the characterization of spiked samples by XAS techniques performed at two synchrotron facilities (ESRF in Grenoble, France and HASYLAB in Hamburg, Germany), as well as bioavailability studies using mercury-specific sensor bacteria. Results show that XAS is a valuable qualitative technique that can be used to identify the bonding character of the Hg in mercury environment. The amount of methyl in mercury adsorbed to montmorillonite was pH-dependent while for all soil components studied, the bond character was not affected by pH. On the other hand, clays exhibited more ionic bonding character than humic acids did with methyl mercury. This interaction has a higher covalent character and so it is more stable for CH₃HgOH than for CH₃HgCl, due to the higher reactivity of the hydroxyl group arising from the possible formation of hydrogen bonds.The bioavailability of methyl mercury adsorbed to montmorillonite, kaolinite and humic acids was measured using recombinant luminescent sensor bacterium Escherichia coli MC1061 (pmerBR_BSluc). In case of contact exposure (suspension assays), the results showed that the bioavailability was higher than it was for exposure to particle-free extracts prepared from these suspensions. The highest bioavailability of methyl mercury was found in suspensions of montmorillonite (about 50% of the total amount), while the bioavailabilities of kaolinite and humic acids were five times lower (about 10%). The behaviour of methyl mercury in the presence of montmorillonite could be explained by the more ionic bonding character of this system, in contrast to the more covalent bonding character observed for humic acids. Thus, XAS techniques seem to provide promising tools for investigating the mechanisms behind the observed bioavailabilities of metals in various environmental matrices, an important topic in environmental toxicology.     

铜锌超氧化物歧化酶(Cu2Zn2SOD)在汞电极上的吸附研究

金属氧化还原蛋白质的电化学行为作为生物电化学领域中一个重要的研究内容,受到了广泛的关注犤1～3犦,生物体系一些重要的反应均与基本电荷运动有关,如生物催化、神经传导、光合作用以及呼吸作用等均涉及到一些重要氧化还原蛋白质的氧化还原过程。利用电化学的基本原理和实验方法,不但能在生命体系和有机组织的整体水平上,更主要是能在分子和细胞水平上研究氧化还原蛋白质体系中的电子转移以及氧化态转化的化学本质和规律。铜锌超氧化物歧化酶(Cu2Zn2SOD)是一个二聚体,由两个等同的亚单位组成,每一个亚单位含有咪唑桥联的铜?和锌?离子,催…     

Mercury Speciation in Fish by High-Performance Liquid Chromatography (HPLC) and Post-Column Ultraviolet (UV)-Photochemical Vapor Generation (PVG): Comparison of Conventional Line-Source and High-Resolution Continuum Source (HR-CS) Atomic Absorption Spectrometry (AAS)

An ultraviolet-photochemical generator (UV-PVG) capable of post-column on-line transformation of both organic and inorganic mercury species to cold vapor (Hg⁰) with subsequent detection by quartz tube-atomic absorption spectrometry (QT-AAS) was developed. Mercury(II), methylmercury(I), ethylmercury(I), and phenylmercury(I) were successfully detected after separation by reversed-phase high-performance liquid chromatography (RP-HPLC). Two types of AAS detectors were compared. The first was a commonly used line-source instrument while the second was a high-resolution continuum source (HR-CS) AAS. The latter provided better limits of detection: 0.47?µg?L^?1 for Hg(II), 0.84?µg?L^?1 for methylmercury(I), 0.80?µg?L^?1 for ethylmercury(I), and 2.0?µg?L^?1 for phenylmercury(I). The repeatability at 30?μg?L^?1 was 3.6%, 4.1%, 6.2%, and 4.5% for these species (n?=?10). These figures of merit were comparable with those reported for more sensitive atomic fluorescence spectrometry. Nine sample extraction procedures were investigated. Extraction by tetramethylammonium hydroxide and HCl at 75?°C was selected as the only method compatible with the proposed separation and detection steps providing high extraction efficiency and no changes in mercury speciation. The applicability of the proposed high-performance liquid chromatography–ultraviolet-photochemical vapor generation–quartz tube-atomic absorption spectrometry method was demonstrated using fish samples and certified reference materials (CRM) DOLT-4 (dogfish liver) and ERM-CE464 (tuna fish). The results were comparable to those obtained by a reference method based on L-cysteine extraction and high-performance liquid chromatography–inductively coupled plasma-mass spectrometry (HPLC–ICP-MS) determination.     

Trimeric perfluoro-ortho-phenylenemercury: a versatile Lewis acidic host

Trimeric perfluoro-ortho-phenylenemercury (1) constitutes one of the simplest trifunctional Lewis acidic hosts. In addition to cooperative effects arising from the proximity of the mercury(II) centers, the electron-withdrawing properties of the backbone and the accessibility of the electrophilic sites lead to the facile complexation of neutral and electron rich substrates. The planarity of the structure as well as its overall polarizability compounded with relativistic effects at mercury also permits the occurrence of non-covalent interactions and accounts for the tendency of this compound to form cofacial dimers. Collectively, the Lewis acidic properties of 1 as well as its ability to engage in non-covalent interactions can be held responsible for its ability to form extended binary supramolecular stacks with arenes. The photoluminescence observed in some of these supramolecular complexes corresponds to the phosphorescence of the aromatic substrate and indicate the occurrence of a mercury heavy atom effect.     

还原气化-原子荧光光谱法快速测定绿色食品基地土壤中的砷与汞

应用还原气化-原子荧光光谱法，使待测元素与基体自动分离、富集，测定绿色食品基地土壤中的AS、HG。经对国家经土壤标准物质进行分析证明，该方法具有快速、准确、灵敏度高等优点，用于绿色食品基地的审评检测，结果令人满意。     

Effects of temperature and anion type on the two-dimensional condensation of the 4,4′-bipyridine cation radical on mercury

The reduction of 4,4′-bipyridine (BPH²⁺₂) on mercury in an acid medium gives a very narrow sharp tail-less reversible voltammetric peak that can be ascribed to the formation of a two-dimensional (2D) phase of the cation radical BPH^·+₂ at the electrode according to the reaction

BPH²⁺₂ + e⁻ |BPH^·+₂|_2D

The corresponding oxidation peak possesses similar properties and arises from the destruction (fusion) of the 2D phase.In this work we studied the influence of some experimental variables, namely the type of anion present in the medium, the concentration of 4,4′-bipyridine and temperature on the 2D phase transition peaks. Also, we tested various analytical criteria to validate this assignation and fitted both voltammetric peaks numerically to the theoretical model developed for this purpose.     

Syntheses and spectroscopic studies on zinc(II) and mercury(II) complexes of isatin-3-thiosemicarbazone

Zinc(II) and mercury(II) complexes were prepared by reacting isatin-3-thiosemicarbazone (ISTSCH) with zinc(II) acetate or mercury(II) bromide. The complexes were characterized by IR, Raman, diffuse reflectance, ¹H and ¹³C NMR spectra and elemental analysis. Tetrahedral structures for Zn(ISTSC)₂ and Hg(ISTSCH)Br₂ are suggested.     

Der erste Polyiodokomplex – Triethylsulfoniumtriiodomercurat(II)-tris(diiod), (Et3S)[Hg2I6]1/2 · 3 I2

The First Polyiodo Complex – Triethylsulfoniumtriiodomercurate(II)-tris(diiodine), (Et₃S)[Hg₂I₆]_1/2 · 3 I₂ After Raman spectroscopic investigation of the system HgI₂/Et₃SI_x, x = 3, 5, 7, triethylsulfoniumtriiodomercuratetris(diiodine), (Et₃S)[Hg₂I₆]_1/2 · 3 I₂ was synthesized by reacting of HgI₂ and liquid Et₃SI₇. The compound crystallizes at room temperature triclinically in the space group P1 with a = 879.4(7), b = 1 209.1(5), c = 1 291.5(5) pm, α = 96.16(3)°, β = 103.82(6)°, γ = 99.05(5)° and Z = 2. The crystal structure is composed of disordered Et₃S⁺ cations, the centrosymmetric complex anion [HgI_2/2I₂]₂^2? and three connecting iodine molecules I₂.     

Comparison of the effectiveness of epoxy cure accelerators using a fluorescent molecular probe

A simple optical method for quantitative comparison of the effectiveness of epoxy cure accelerators, used for speeding up the crosslinking process of epoxy resins with cyclic anhydrides, is described. Fluorescent molecular probes and a miniature fiber optic spectrometer have been applied for measurement of the cure kinetics of a model epoxy resin/anhydride composition in the presence of various cure accelerators. A quantitative index of accelerator performance has been determined for several of the most common accelerators.