Integrated biological–chemical approach for the isolation and selection of polyaromatic mutagens in surface waters

Many environmental mutagens, including polyaromatic compounds are present in surface waters, often in complex mixtures and at low concentrations. The present study provides and applies a novel, integrated approach to isolate polyaromatic mutagens in river water using a sample from the River Elbe. The sample was taken downstream of industrial discharges using blue rayon (BR) as a passive sampler that selectively adsorbs polyaromatic compounds and was subjected to effect-directed fractionation in order to characterise the compounds causing the detected effect(s). The procedure relies on three complementary fractionation steps, the Ames fluctuation assay with strains TA98, YG1024 and YG1041 with and without S9 activation and analytical screening. Several mutagenic fractions were isolated by combining mutagenicity testing with fractionation. The enhanced mutagenicity in the nitroreductase and/or O-acetyltransferase overexpressing strains YG1024 and YG1041 strains suggested amino- and/or nitro-compounds causing mutagenicity in several fractions. Analytical screening of mutagenic fractions with LC-HRMS/MS provided a list of molecular formulas typically containing one to ten nitrogen and at least two oxygen atoms supporting the presence of amino and nitro-compounds in the mutagenic fractions.

Gas chromatographic–mass spectrometric methodology using solid-phase microextraction for the multiresidue determination of pesticides in surface waters

Solid-phase microextraction (SPME) coupled with gas chromatography–mass spectrometry (GC–MS) and selected ion monitoring (SIM) was used for the analytical determination of priority pesticide residues. Fibers coated with a 65-µm film thickness of polydimethylsiloxane divinylbenzene (PDMS-DVB) were used to extract 31 pesticides of different chemical groups. The quality parameters of the method demonstrated a good precision with detection limits of 1–56?ng/L. Linearity was controlled in the range of 0.1–50?µg/L. The proposed method was applied for the trace-level determination of the target pesticides in surface water samples including three rivers and one lake at the Epirus region (north-west Greece) for a period of one year. The results demonstrate the suitability of the SPME–GC–MS approach for the analysis of multi-residue pesticides in environmental water samples.     

Characterization of reused U–10Zr heel residue containing rare-earth elements through surface treatment

Journal of Radioanalytical and Nuclear Chemistry - U–Zr–RE heel residue was manufactured after fabricating U–Zr–RE fuel slugs by an injection casting method. In order to...     

Studies of surface alloy as high efficient electrocatalyst for glyoxylic acid synthesis

运用电化学方法，研制了三种表面合金（ＰｂＳｂＰｔ／ＧＣ，ＳｂＰｔ／ＧＣ，ＰｂＰｔ／ＧＣ）电催化剂，发现在草酸还原生成乙醛酸的电有机合成中这些表面合金电催化剂有较高的活性，其起始还原电位分别比在Ｐｂ阴极上（１．１Ｖ）提前了０．４８～０．７０Ｖ。这三种表面合金电催化剂的活性次序为：ＰｂＳｂＰｔ／ＧＣ＞ＳｂＰｔ／ＧＣ＞ＰｂＰｔ／ＧＣ。红外光谱结果表明，在这些表面合金电极上草酸还原产物主要为乙醛酸。     

Construction of hierarchical porous graphene–carbon nanotubes hybrid with high surface area for high performance supercapacitor applications

Journal of Solid State Electrochemistry - Unlike activated carbon, graphene sheets are lack of ion pathways on their basal planes and prone to agglomerate or restack unfortunately for their strong...     

Manipulation of the PdAu‒PdAuOx interface on Pd-Au bimetallic catalysts for the direct synthesis of hydrogen peroxide

Direct synthesis of H₂O₂ from H₂ and O₂ via heterogeneous catalysis is an environmentally friendly and atomically economic alternative to the traditional anthraquinone oxidation (AO) process. Optimizing the electronic and geometric structures of the active metals to break the current limitations of hydrogenation rate and H₂O₂ selectivity is a promising and challenging topic. In this study, a series of Pd-Au bimetallic catalysts supported on TiO₂ with a metal loading of 3.0 wt% and a constant Pd/Au molar ratio (Pd:Au = 2:1) were prepared. The catalysts were reduced in H₂ at different temperatures (473, 573 and 673 K), and their catalytic activity for the direct H₂O₂ synthesis were evaluated at 283 K and 0.1 MPa. H₂ reduced Pd-Au catalysts exhibited superior performance in direct H₂O₂ synthesis. The maximum H₂O₂ selectivity of 87.7% and H₂O₂ yield of 3116.4 mmol h⁻¹ g_Pd⁻¹ were achieved over the Pd_2.0Au_1.0-573 catalyst with a H₂ conversion of 12.8%. The tailored local chemical environment caused by H₂ reduction creates a balanced ratio of Pd⁰ and PdO_x sites, thus improving the selectivity towards H₂O₂. This work developed an effective strategy for fabrication of highly active and stable Pd-based H₂O₂ synthesis catalysts with high H₂O₂ yield.     

Dynamics of the surface layer in cyanobiphenyl–aerosil nanocomposites with a high silica density

Composites were prepared from an aerosil and 4-n-alkyl-4′cyanobiphenyls with five to eight carbon atoms in the alkyl chain. Their high silica density of ～7?g aerosil in 1?cm³ of liquid crystal (LC) allows the observation of the behaviour of a thin cyanobiphenyl layer (having nearly a monolayer structure) on the silica particles. The systems are investigated by dielectric spectroscopy (10^?2–10⁹?Hz) in a large temperature range (220–370?K). All the composites show a (main) relaxation process at frequencies much lower than the processes observed for the bulk LC that was assigned to the dynamics of the molecules in the surface layer. The temperature dependence of its characteristic frequencies obeys the Vogel–Fulcher–Tammann law, which is found to be typical for glass-forming liquids. The quasi two-dimensional character of the glass transition in the surface layer is discussed for the first time. At the nematic-to-isotropic transition temperature of the bulk, the composites show a continuous decrease of the characteristic frequencies as a function of the alkyl chain length, while the bulk LCs show the well known odd–even behaviour. The magnitude and temperature dependence of the slow relaxation process in the composites (molecules on an outer surface) agree with those of the same molecules confined to the nanopores of molecular sieves (internal surface).     

Template-free sol–gel synthesis of high surface area mesoporous silica based catalysts for esterification of di-carboxylic acids

High surface area mesoporous silica based catalysts have been prepared by a simple hydrolysis/sol–gel process without using any organic template and hydrothermal treatment. A controlled hydrolysis of ethyl silicate-40, an industrial bulk chemical, as a silica precursor, resulted in the formation of very high surface area (719 m²/g) mesoporous (pore size 67 Å and pore volume 1.19 cc/g) silica. The formation of mesoporous silica has been correlated with the polymeric nature of the ethyl silicate-40 silica precursor which on hydrolysis and further condensation forms long chain silica species which hinders the formation of a close condensed structure thus creating larger pores resulting in the formation of high surface mesoporous silica. Ethyl silicate-40 was used further for preparing a solid acid catalyst by supporting molybdenum oxide nanoparticles on mesoporous silica by a simple hydrolysis sol–gel synthesis procedure. The catalysts showed very high acidity as determined by NH₃-TPD with the presence of Lewis as well as Brønsted acidity. These catalysts showed very high catalytic activity for esterification; a typical acid catalyzed organic transformation of various mono- and di-carboxylic acids with a range of alcohols. The in situ formed silicomolybdic acid heteropoly-anion species during the catalytic reactions were found to be catalytically active species for these reactions. Ethyl silicate-40, an industrial bulk silica precursor, has shown a good potential for its use as a silica precursor for the preparation of mesoporous silica based heterogeneous catalysts on a larger scale at a lower cost.     

Is the A-ring of sparteine essential for high enantioselectivity in the asymmetric lithiation-substitution of N-Boc-pyrrolidine?

The simplest chiral portion of sparteine, N,N'-dimethyl-2-endo-methylbispidine, was prepared and evaluated in the asymmetric lithiation-substitution of N-Boc-pyrrolidine. The results indicate that the complete A-ring of sparteine is essential for high levels of asymmetric induction. DFT-QSSR analyses of the diamine/Li(+) complexes and DFT calculations of the pertinent i-PrLi/diamine/N-Boc-pyrrolidine complexes are predictive and provide complementary pictures of the stereochemical features critical to this transformation.     

Micro–nano structural engineering of filter paper surface for high selective oil–water separation

Cellulose-based lotus-leaf-like filter paper for selective separation of oil/water was prepared. Experimentally, cellulose nanofibril aerogel microspheres prepared by ultrasonic atomization method were coated on commercial filter papers to form unique “micro–nano” structured surface. By controlling both the morphology and chemistry of the surface, the papers could be either under-water superoleophobic or under-oil superhydrophobic. It was found that the filter papers could be engineered to effectively filter only oil or only water from their mixtures.     

Well-oriented ZZ–PS-tag with high Fc-binding onto polystyrene surface for controlled immobilization of capture antibodies

The site specificity and bioactivity retention of antibodies immobilized on a solid substrate are crucial requirements for solid phase immunoassays. A fusion protein between an immunoglobulin G (IgG)-binding protein (ZZ protein) and a polystyrene-binding peptide (PS-tag) was constructed, and then used to develop a simple method for the oriented immobilization of the ZZ protein onto a PS support by the specific attachment of the PS-tag onto a hydrophilic PS. The orientation of intact IgG was achieved via the interaction of the ZZ protein and the constant fragment (Fc), thereby displayed the Fab fragment for binding antigen. The interaction between rabbit IgG anti-horseradish peroxidase (anti-HRP) and its binding partner HRP was analyzed. Results showed that the oriented ZZ–PS-tag yielded an IgG-binding activity that is fivefold higher than that produced by the passive immobilization of the ZZ protein. The advantage of the proposed immunoassay strategy was demonstrated through an enzyme-linked immunosorbent assay, in which monoclonal mouse anti-goat IgG and HRP-conjugated rabbit F(ab′)₂ anti-goat IgG were used to detect goat IgG. The ZZ–PS-tag presented a tenfold higher sensitivity and a wider linear range than did the passively immobilized ZZ protein. The proposed approach may be an attractive strategy for a broad range of applications involving the oriented immobilization of intact IgGs onto PS supports, in which only one type of phi-PS (ZZ–PS-tag) surface is used.     

Preparation and optimization of colon-targeted Pectin-Chitosan microsphere containing Diloxanide furoate-hydroxypropyl-β-cyclodextrin inclusion complex for effective treatment of amoebiasis

Degradation in the upper gastrointestinal tract increases the unwanted dose of Diloxanide furoate.(DF) as an anti-amoebic drug, the use of colonic delivery of it is a promising approach to reduce its dose and dose-dependent side effects. An investigation was done to prepare and evaluate the microsphere for site-specific delivery using surface response curve methodology to optimize independent variables like concentration of polymer (Pectin and Chitosan), crosslinking agent, and time of hardening and the dependent variable like percentage drug entrapment and drug release in an acidic environment. The microsphere was prepared by dropping of optimized inclusion complex of DF and hydroxypropyl-β-cyclodextrin with anionic polymer (Pectin) to a solution of cationic polymer containing different concentrations of calcium chloride. Prepared microspheres were characterized by swelling behavior, In vitro release in various simulated gastric and intestine fluids. The results suggest that pectin 6%, Chitosan 3.5%, CaCl₂ 6%, and cross-linking time 20 min shows a promising approach to colonic delivery of DF for not only better retreatment of amoebiasis but also for reducing dose-related side effects.     

Application of γ-cyclodextrin for the stabilization and/or dispersion of vegetable oils containing triglycerides of

To improve the storage stability of instable vegetable oils with a high content of polyunsaturated fatty acid triglycerides, these essential compounds can be complexed with native cyclodextrins. Only with -CD a nearly complete complexation of the oils was achieved as shown by complexation kinetics measurements. Storage trials of the insoluble CD-complexes followed by the determination of the peroxide value of the oils indicated that the best stabilization against autoxidation is obtained with -CD. An additional benefit of the complexation of triglycerides of polyunsaturated fatty acids with -cyclodextrin is the formation of stable dispersions of these oils in aqueous media.     

Spectrofluorometric method for determination of the total mercury content in environmental samples — Waste waters

A highly selective spectrofluorometric method for the determination of total mercury (Hg) in waste waters is described. Fluorescence quenching of rhodamine B with Hg(II) in the presence of iodide, after a concentration step, is the basis of this sensitive method. All forms of mercury, including organic compounds, are pre-oxidized to ionic mercury by acidic potassium permanganate. The final and complete oxidation is achieved by adding potassium persulphate and heating. Hg(II) was reduced by tin(II) chloride and Hg vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. In this solution fluorescence quenching of rhodamine B at an excitation wavelength of 485 nm and emission wavelength of 586 nm was measured. The recoveries were done by adding 3.0 g Hg/100 ml to each sample before the digestion. It was indicated that the recoveries for determining mercury in waste waters were 98.3%–102.7%. The method gives reliable results down to a concentration of 10 ng Hg/ml waste water.     

An SCF-CI method for determining the potential energy surface of a triatomic molecule

A self-consistent-field (SCF)-configuration interaction (CI) (SCF-CI) method for determining the potential energy surface of a triatomic molecule from the observed vibrational band origins has been suggested. By this method, the SCF-CI procedure in the internal coordinates is used to calculate the vibrational bond origins and their first derivatives with respect to parameters in the potential energy function using the exact vibrational Hamiltonian, and the optimizer LMF in the nonlinear-squares problem is employed to optimize parameters in the potential energy function. This approach is used to optimize the potential energy function of the water molecule. The standard deviation of this fitting to the 70 observed band origins is 1.154cm-1.     

Integrated procedure for determination of endocrine-disrupting activity in surface waters and sediments by use of the biological technique recombinant yeast assay and chemical analysis by LC–ESI-MS

An integrated procedure using mass spectrometry and molecular biology for determination of estrogenicity in natural waters and sediments is reported. Solid-phase extraction (SPE) and pressurized-liquid extraction (PLE), respectively, were used for isolation of endocrine-disrupting compounds (EDC) from surface waters and sediments, followed by liquid chromatography–mass spectrometry using an electrospray interface (LC–ESI-MS). Twenty seven EDC were determined: non-ionic surfactants (nonylphenol ethoxylate), alkylphenols (e.g. nonylphenol and octylphenol), bisphenol A, phthalates, and natural and synthetic steroid sex hormones. Limits of detection varied from 0.02 to 0.22 g L^–1 and from 1 to 10 g kg^–1 in water and sediments, respectively. Recoveries ranged from 65 to 125% and 73 to 97% for waters and sediments, respectively. In addition to LC–ESI-MS determination, extracts obtained by SPE and PLE were analyzed by the recombinant yeast assay (RYA) to assess total estrogenic activity. This bioassay detects natural estrogens and xenoestrogens, producing a quantitative measurement of EDC irrespective of the identity of the chemical responsible for the activity. As a novelty, a relative estrogenicity factor was determined for 19 analytes with EC ₅₀ values ranging from 10^–10 to 10^–9 mol L^–1 for synthetic estrogens, from 10^–7 to 10^–5 mol L^–1 for alkylphenol derivatives, and from 10^–5 to 10^–4 mol L^–1 for phthalates and benzothiazoles. By use of this integrated chemical–ecotoxicological approach good correlation was usually established between chemical composition and estrogenic effects for surface water and sediment samples from Portugal. Estrogenic activity observed was mainly attributed to the presence of nonylphenolic compounds (with concentrations of NP ranging from 0.1 up to 44 g L^–1 in waters and up to 1172 g kg^–1 in sediments), and to the sporadic presence of estrogens, detected at ng L^–1 levels.     

Two-step high order hybrid explicit method for the numerical solution of the Schrödinger equation

In this paper we present a new method for the numerical solution of the time-independent Schrödinger equation for one spatial dimension and related problems. A technique, based on the phase-lag and its derivatives, is used, in order to calculate the parameters of the new Numerov-type algorithm. We study the relation of the local truncation error with the energy of the model of the radial Schrödinger equation and via this investigation we examine how accurate is the new method compared with other well known numerical methods in the literature. We present also the stability analysis of the new method and the relation of the interval of periodicity with the frequency of the test problem and the frequency of the new developed method. We illustrate the accuracy and computational efficiency of the new developed method via numerical examples.     

Assessment of surface heterogeneity of calcite and apatite: from high resolution gas adsorption to the solid–liquid interface

The surface heterogeneity of calcite and apatite was investigated by high resolution adsorption isotherms of argon and nitrogen. The use of the derivative isotherm summation procedure reveals the presence of high energy adsorption sites for nitrogen molecules. These sites are assigned to surface calciums and monohydrogenophosphate groups for calcite and apatite respectively. The comparison of gas adsorption results with experiments at solid–liquid interfaces shows that nitrogen probes the same surface sites as benzoic acid on calcite and decylammonium chloride on apatite.     

Violation of Environmental Standards for Inorganic Nitrogen Compounds in Glacial Rivers of the Central Caucasus in 2017‒2019

Russian Journal of General Chemistry - The results of monitoring of the concentrations of nitrates, nitrites, and ammonium nitrogen in glacial rivers of the Central Caucasus during the winter...