Analysis of phenols in water by high-performance liquid chromatography using coumarin-6-sulfonyl chloride as a fluorogenic precolumn label

A simple, sensitive and rapid reversed-phase high-performance liquid chromatography (RP-HPLC) method is proposed for the analysis of some environmentally important phenols in water. The use of coumarin-6-sulphonyl chloride (C6SCl) as a fluorescence-labeling reagent has been investigated. The compound reacts with phenols within 20 min under mild conditions (ambient temperature, pH 9.0) to give sulphonates that can be separated by RP-HPLC employing fluorescence detection at lambda(ex) = 360 and lambda(em) = 460 nm. The optimum conditions for fluorescence, derivatization and chromatographic separation have been established and detection limits in the range 0.1-0.9 microg l(-1) were obtained for the studied compounds. The calibration curves were linear for the range 6-200 microg l(-1) for phenol, 3-200 microg l(-1) for 2-chlorophenol, 4-chlorophenol and 2,3,5-trichlorophenol and for the range of 3-100 microg l(-1) for 2,3-dichlorophenol and 3,5-dichlorophenol. The practical applicability of the method to environmental samples was demonstrated by analyzing drinking and industrial water samples spiked with the phenolic compounds.     

Isomerism of low-lying states in 86Y

Low-energy isomeric states of ⁸⁶Y were populated in the reaction ⁷³Ge + ¹⁶O at 57MeV and were investigated by means of delayed n $ \gamma$ and $ \gamma$ $ \gamma$ coincidences. A half-life of 70(7)ns was measured for the 5^- state at 208keV, yielding an exceptionally small B(M1) value of 2.0(7)×10^-5 W.u. and a B(E2) value of 0.34(⁺²⁴ _-13) W.u. For the other three known isomeric states at 218, 243, and 302keV, the half-lives extracted from the present experimental data are in very good agreement with previous measurements. Given the newly observed isomeric character of the 5^- 208keV state, the re-analysis of earlier experimental data on the 302keV isomer led to a new spin-parity assignment, 6⁺, for this state. In addition, this re-evaluation provided two g -factors, -0.083(3) and +0.63(2) , for the 208 and 302keV states, respectively. The results are discussed in terms of spherical-shell model calculations performed with a truncated space of configurations built on the f _5/2 , p _3/2 , p _1/2 , and g _9/2 valence orbitals. Effective spin, orbital, and “tensor” g -factors were determined empirically for protons and neutrons in the considered configuration space.     

Gamma-ray spectroscopy of the nucleus 139Ce

Gamma-ray coincidence techniques are used to determine new level structures in the N = 81 nucleus ¹³⁹Ce, at low spins and excitation energies with the ¹³⁹La(p, nγ) reaction at 5.0 and 6.0MeV incident energy, and at high spins with the ¹³⁰Te(¹²C, 3nγ) reaction at 50.5MeV, respectively. Lifetime determinations are also made in the (p, nγ) reaction with the centroid DSA method. The observed level structures are discussed by comparison with existing calculations and with those in the neighbouring nucleus ¹⁴⁰Ce.     

Halpern- and Mann-Type Algorithms for Fixed Points and Inclusion Problems on Hadamard Manifolds

In this article, we consider an inclusion problem which is defined by means of a sum of a single-valued vector field and a set-valued vector field defined on a Hadamard manifold. We propose Halpern-type and Mann-type algorithms for finding a common point of the set of fixed points of a nonexpansive mapping and the set of solutions of the inclusion problem defined on a Hadamard manifold. Some particular cases of our problem and algorithm are also discussed. We study the convergence of the proposed algorithm to a common point of the set of fixed points of a nonexpansive mapping and the set of solutions of the inclusion problem defined on a Hadamard manifold. As applications of our results and algorithms, we derive the solution methods and their convergence results for the optimization problems, variational inequality problems and equilibrium problems in the setting of Hadamard manifolds.     

On the 0.34 eV hole trap in irradiated boron-doped silicon

Abstract

A detailed deep level transient spectroscopy (DLTS) study has been carried out on a prominant hole trap at 0.34 eV above the valence band in irradiated p-type silicon. The boron concentration in the float zone and Czochralski-grown samples varied between 10¹² and 10¹⁶ cm^?3, and irradiations with 2.0 MeV electrons have been performed at nominal room temperature to total fluences of 1.0 × 10¹⁶ and 1.0 × 10¹⁷ e^?/cm². The introduction rate of the trap is strongly boron-dependent, while the oxygen content in the samples does not influence neither the trap production rate nor its observed annealing behaviour. In the light of these observations and other available data on this trap, a boron-carbon pair is here tentatively proposed as the defect identity. A previously unreported hole trap at 0.45 eV above the valence band has also been observed in this work in highly boron-doped material. The isothermal and isochronal annealing characteristics of both traps have been investigated up to 400°C.     

Novel Pyrazoline‐based Organometallic Compounds Containing Ferrocenyl and Quinoline units: Synthesis,Characterization and Microbial susceptibilities

Some novel pyrazoline‐based organometallic compounds were synthesized as new leads in antimicrobial chemotherapy. The structures of compounds were elucidated by different spectroscopic techniques and elemental analyses. All compounds were investigated for in vitro antimicrobial studies against fifteen ATTC bacterial and fungal strains. The microbial susceptibility of these compounds revealed that all the tested compounds gave good minimum inhibitory concentration (MIC) values against the tested organisms that are either similar or even better than the reference drugs amoxicillin and fluconazole, which gave MIC values 8‐64 μg/ml against bacterial and 64 μg/ml against fungal strains, respectively. Among all compounds, compound ( 4d ) 1‐(5‐(4‐chlorophenyl)‐3‐ferrocenyl‐4,5‐dihydropyrazol‐1‐yl)‐2‐quinolin‐8‐yloxy) ethanone, emerged out the most promising antimicrobial organometallic derivative with MIC values against all the strains ranging from 8‐32 μg/ml. Other compounds gave a range of MIC values between 16‐64 μg/ml against S. bovis, 16‐32 μg/ml against E. coli, and C. tropicalis except compound ( 4d) which gave MIC 8 μg/ml against S. bovis and E. coli, whereas 32 μg/ml against C. tropicalis. Collectively, these compounds gave a lower MIC value between 32‐64 μg/ml against both of the biofilm forming strains namely, P. aeruginosa and S. mutans. The results of microbial susceptibility concluded that these novel organometallic compounds are new leads in antimicrobial chemotherapy and can be very useful for further optimization work on microbial chemotherapy.     

Off-line optimization of the separation of 2,4-dinitrophenylhydrazones by gas chromatography using chemometric techniques

An off-line optimization technique based on soft modeling methods has been used to determine the optimum conditions for the separation of eight carbonyl-2,4-dinitrophenylhydrazones by gas chromatography equipped with a nitrogen-phosphorous detector. In this method theoretical simulations of peak retention time and peak width at base-line are coupled to a factorial design to map the chromatographic response surface. The calculated retention times from isothermal data have been used to calculate the chromatographic parameters. A full 3(3) factorial design was used to locate the optimum conditions for the temperature program, utilizing initial oven temperature, T(i), the programming rate for the first ramp, PR(1), and the programming rate for the second ramp, PR(2) as independent variables. The optimum conditions obtained for these parameters were: T(i), 140 degrees C; PR(1), 12 degrees Cmin(-1); PR(2), 8 degrees Cmin(-1). The maximum analysis times achieved by this optimum was 10.6 min.     

A sequential injection method for the fluorimetric determination of aluminum in drinking water using 8-hydroxy-7-(4-sulfo-1-naphthylazo)-5-quinoline sulfonic acid

A robust and simple sequential injection (SI) method for the assay of aluminum ions in drinking water is described. The method is based on the complex formation between aluminum and 8-hydroxy-7-(4-sulfo-1-naphthylazo)-5-quinoline sulfonic acid (HSNQ). The fluorescence of the complex is monitored at an emission wavelength of 492 nm with excitation at 357 nm. The HSNQ concentration, aspirated reagent and sample volumes were optimized simultaneously using 3(3) full factorial design. The optimum operating conditions are aspirated sample and reagent volumes of 90 and 70 microL, respectively, and HSNQ concentration of 20 microM. With these conditions linear calibration curves were obtained from 100 to 800 ppb. The detection limit was 4 ppb. The maximum relative standard deviation of the method was 1.43% (n=5). The method was successfully applied for the determination of aluminum in drinking water samples.     

Droplet Flow Assisted Electrocatalytic Oxidation of Selected Alcohols under Ambient Condition

This study reports using a droplet flow assisted mechanism to enhance the electrocatalytic oxidation of benzyl alcohol, 2-phenoxyethanol, and hydroxymethylfurfural at room temperature. Cobalt phosphide (CoP) was employed as an active electrocatalyst to promote the oxidation of each of the individual substrates. Surface analysis of the CoP electrocatalyst using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), as well as electrochemical characterization, revealed that it had excellent catalytic activity for each of the substrates studied. The combined droplet flow with the continuous flow electrochemical oxidation approach significantly enhanced the conversion and selectivity of the transformation reactions. The results of this investigation show that at an electrolysis potential of 1.3 V and ambient conditions, both the selectivity and yield of aldehyde from substrate conversion can reach 97.0%.