Coadsorption of carbofuran and lead at the water/silica interface. Possible impact on environment

Despite its extremely weak adsorption at the water/silica interface, carbofuran can, however, induce the coadsorption of metallic salts, like, for example, lead nitrate, and thus enhance its adsorption. We quantitatively studied this phenomenon with a depletion method and under concentration conditions close to the environmental ones. Heavy metal salt was found to positively adsorb, whereas carbofuran relative adsorption is generally slightly negative. This study provides evidence that considering these facts is of paramount importance in environmental prospects. To cite this article: G. Elmanfe et al., C. R. Chimie 9 (2006).     

A Restudy of Direct Chelatometric Titration of Vanadium(IV) with N-Benzoyl-N-phenylhydroxylamine as Indicator

This paper restudies the method of direct chelatometric titration of V(IV) with N-benzoyl-N-phenylhydroxylamine (BPHA) as indicator. The indicator functions entirely differently from indicators hitherto used in chelatometry. The solution contains two independent systems – the indicator and the titrand-titrant system – without any color changing species. The BPHA-V(V) chelate once formed as the result of aerial oxidation constitutes the indicator system and does not react with EDTA. Its color therefore remains unchanged throughout titration. It is not a metallochromic indicator. Its function is that of color-screening. The color of the titrant system deepens during titration, but does not change. The end-point is indicated by one color completely covering up the other. Hence, this method is of purely empirical nature.Received July 5, 2002; accepted February 11, 2003 Published online July 16, 2003     

Study of the Fluorescence System of Europium–Enoxacin and its Applications

 This paper is the study of the fluorescence enhancement of Eu³⁺-1-ethyl-6-fluoro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridin-3-carbonic acid (enoxacin, EFLX) system by surfactants. It was found that sodium dodecylbenzenesulfonate (SDBS) exhibits great enhancement on the fluorescence of the Eu-EFLX system. The molar ratio is 1:2:1 for Eu:EFLX: SDBS. Under the optimum conditions, the fluorescence intensity is a linear function of europium in the range of 1.0 × 10⁻⁸ ∼ 5.0 × 10⁻⁶ mol/L, the detection limit is 1.0 × 10⁻⁹ mol/L. The application of the Eu-EFLX-SDBS system for the determination of trace europium in rare earth samples gave satisfactory results. Received October 19, 2000. Revision August 10, 2001.     

Antiferromagnetic complexes involving metal---metal bonds III. Synthesis, structure and magnetic properties of heterotrinuclear complexes of the type M(CO)5L (M = Cr, Mo and w) containing [(C5H5CrSCMe3)2S] as unusual antiferromagnetic ligand L

Isostructural heterotrinuclear complexes (C₅H₅CrSCMe₃)₂S · M(CO)₅ (II–IV) were isolated from photochemical reactions between the antiferromagnetic complex (C₅H₅CrSCMe₃)₂S (I) (with the Cr---Cr bond 2.689 Å long and with the exchange parameter −2J = 430 cm⁻¹) and metal hexacarbonyls, M(CO)₆, where M is Cr, Mo, or W. According to the X-ray structural data on III and IV, complex I plays the role of an unusual antiferromagnetic ligand L bound to M through the sulphide bridge (M–S 2.58(2) Å). Its geometry remains practically unaffected by the complex formation (the Cr---Cr bond length in III and IV is 2.73(1) Å). The exchange parameter, −2J (410, 440 and 440 cm⁻¹ in II to IV, respectively), also shifts only insignificantly from that of I, which probably means that indirect exchange via the sulphide bridge in I is of minor importance compared with the direct Cr---Cr exchange. The Cr---Cr bond length may thus be correlated with the observed overall exchange coupling.     

Functionalized Self-Assembled Monolayers on Gold as Binding Matrices for the Screening of Antibody-Antigen Interactions

Two different types of -substituted alkanethiol/disulfide compounds have been used to prepare monolayer architectures on gold serving as platforms for the immobilization of receptor probe molecules – antibodies. These are: (i) carboxylic acid alkanethiols post-reacted with amino biotin to generate streptavidin surfaces, and (ii) N-hydroxysuccinimide-terminated disulfide surfaces. The properties of the monolayers, with and without attached receptor probe molecules, were analysed using infrared spectroscopy, ellipsometry, fluorescence scanning and atomic force microscopy. Several experimental parameters, such as condensation reagents, additives, probe and target concentrations and immobilization time, were systematically varied to determine the dynamic range and to optimize the sensitivity and signal-to-noise ratio of the biochip platforms. Fluorescence screening using Cy5-labelled antigens finally demonstrated that both surfaces could be successfully employed to immobilize the antibodies. The pros and cons of the two approaches are also discussed.Received November 15, 2002; accepted March 25, 2003 Published online July 28, 2003     

Oxythallation of norbornene derivatives with thallium(III) acetate in methanol

Treatment of norbornene, norbornadiene, benzonorbornadiene, and chloro- and methoxy-benzonorbornadiene with thallium(III) acetate in methanol affords only the corresponding cis-exo-acetoxythallation adducts in a sharp contrast to oxymercuration of such strained olefins where methoxymercuration prevails. In the cases of substituted benzonorbornadienes the products are obtained as the regioisomeric mixtures, the isomer ratio being determined by ¹³C NMR. In the cases of 5-norbornene-2,3-dicarboxylic anhydride, 5-norbornene-2-methyl-2,3-dicarboxylic anhydride, and 5-norbornen-2-endo-carboxylic acid, lactonization occurs to give a trans-oxythallation adduct having a lactone ring, no introduction of either methoxy or acetoxy groups being observed. ¹H and/or ¹³C NMR data for several new oxythallation adducts are provided. The alkaline sodium borohydride reduction of adducts in methanol affords mainly the parent olefin together with 10–16% yields of the corresponding exo-alcohol.     

Stochastic model of dissociation-recombination kinetics in micelles

The small number of reagents solubilized in a micelle prohibits the use of conventional reaction kinetics. In order to describe the kinetics of the reaction A + B ? AB proceeding in a micellar phase, a stochastic model is evaluated. The deviation of these results from those obtained by conventional kinetics may be as high as 20%.     

Adsorption of N-Nitrosodiethylamine and N-Nitrosodimethylamine on Activated Carbon: A Pre-Concentration Procedure for Gas Chromatographic Analysis

In this study, a rapid pre-concentration procedure, which employs powdered activated carbon as a clean-up and pre-concentration material, is described for the gas chromatographic analysis of N-nitrosodiethylamine (NDEA) and N-nitrosodimethylamine (NDMA) in aqueous solutions. It was found that powdered activated carbon is suitable for the adsorption of volatile N-nitrosamine compounds from aqueous solutions. Adsorption efficiency with spiked beer samples (alcohol content 5% v/v) was found to be 80.5% (NDMA) and 89.4% (NDEA) and recovery of extraction from activated carbon was calculated as 82.1% (NDMA) and 89.7% (NDEA), respectively. The effect of 100µgmL^–1 of tannic acid on the adsorption was also studied, and no significant effect on the adsorption and extraction of volatile N-nitrosamine compounds was found.     

Theoretical Study on the Structures and Electronic Spectra of the Derivatives of C_(60)-P-2,4,6-Triphenyl Borazinc

1 INTRODUCTION The electron-transfer reaction of C60 derivatives, especially light-induced electron-transfer reaction, has been an active research field for a long time. Many researches are focused on the long-live charge- separated state caused by electron-transfer[1]. And several electron-transfers between electron donor and C60 or intramolecular electron-transfer have been confirmed. As an example, TTF-C60 is proved to be a short-live charge-separated compound[2].Due to the excelle…     

Chiral discrimination ofN-(dansyl)-dl-amino acids on human serum albumin stationary phase: Effect of a mobile phase modifier

Summary The effect of perchlorate anion as mobile phase modifier on the separation factor, α, forN-(dansyl)-dl-norvaline andN-(dansyl)-dl-tryptophan on a human serum albumin (HSA) column was studied by varying the concentration,c, of the chaotropic agent and the column temperatureT. Gibbs-Helmholtz parameters Δ(ΔH) and Δ(ΔS) between thed andl enantiomers were determined from linear van't Hoff plots of lnα against 1/T. Thermodynamic results indicated that the enhancement of the separation factor observed asc was increased was enthalpically controlled owing to stereoselective H-bonding interactions. Such behavior was used to optimize the chromatographic conditions for separation ofN-(dansyl)-amino acids on HSA.