Some ion-exchange resins for anion-chromatography

The quaternary ammonium salts, n-butyltrimethylammonium iodide, 1,1,3,3-tetramethylbutyltrimethylammonium iodide, n-octadecyltrimethylammonium iodide and tri-n-dodecylmethylammonium iodide were synthesized from commercially available amines and together with n-hexadecyltrimethylammonium bromide tested for retention by a series of macroreticular resins (XAD-2, XAD-4, XAD-7, XAD-8 and XAD-11) for use as "surface" ion-exchangers in the chromatography of anions. Exchange-capacity studies of the coated resins showed that the non-polar XAD-2 and XAD-4 resins had retention characteristics superior to those of the polar resins and that pore size in the resin was more important than surface area per unit weight of resin. Tri-n-dodecylmethylammonium salts in XAD-2 gave the highest exchange capacity, with best retention under elution conditions. Columns prepared from this anion-exchanger were used to separate and analyse simple mixtures of anions (chloride, nitrate and sulphate) each within the 1-30 ppm range, by single-column operation with indirect photometric detection and also by conductivity detection with background-ion suppression. Though of use for the determination of anions in simple mixtures, the resolution and performance were generally poorer than those displayed by a commercial (Dionex) column. This is at least partly attributable to the inferior column-packing properties of the granular XAD-resin.     

Quantitative determination of organochlorine pesticides in sewage sludges using soxtec,soxhlet and pressurized liquid extractions and ion trap mass–mass spectrometric detection

A new analytical method is described for the determination of organochlorine pesticides (OCPs) in sewage sludges using GC-ion trap-MS–MS. In this work, 16 organo-chlorine pesticides (OCPs) listed by the US Environmental Protection Agency (US EPA) as priority pollutants were separated and quantified. Sludge samples from three of Kuwaits wastewater treatment plants (WWTPs) were analyzed for organochlorine pesticides (OCPs). Spiked sludge samples were extracted with a mixture of (1:1 v/v) dichloromethane (DCM)/hexane. The extracts were cleaned on a silica/aluminum oxide column, then transferred to a gel permeation chromatography (GPC) column, before undergoing further silica/aluminum oxide clean-up; the presence of OCPs was then confirmed by GC-ion trap-MS–MS. Three extraction techniques, soxtec, soxhlet, and pressurized liquid extractions were utilized, compared and validated using the spiked sludge samples. The methods were validated in term of accuracy (recovery) and precision (RSD). The method recovery values varyied from 76.1 to 92.9% for the three extraction techniques.     

Catalytic comparison of various polar Zn(II)-Schiff base complexes and VO(II)-Schiff base complexes in (ep)oxidation processes of 1,2-cyclohexene and cyclohexane

Research on Chemical Intermediates - The reactivity of Zn2+ and VO2+ ions towards pyridinyl Schiff bases, in the absence or presence of a p-sodium sulfonate group (HPSNa and HPS, respectively),...     

A partial derivatives approach for estimation of the viscosity Arrhenius temperature in N,N-dimethylformamide + 1,4-dioxane binary fluid mixtures at temperatures from 298.15 K to 318.15 K

Excess properties calculated from the literature values of experimental density and viscosity in N,N-dimethylformamide (DMF) + 1,4-dioxane (DO) fluid binary mixtures (from 303.15 to 318.15) K can lead us to test the different correlation equations as well as their corresponding relative functions. Inspection of the Arrhenius activation energy Ea and the enthalpy of activation of viscous flow ?H* shows very close values; here we can define partial molar activation energy Ea₁ and Ea₂ for DMF and DO, respectively, along with their individual contribution separately. Correlation between the two Arrhenius parameters of viscosity in all compositions shows the existence of the primary distinct behaviours separated by particular mole fractions in DMF. In addition, we add that the correlation between Arrhenius parameters reveals interesting Arrhenius temperature (T_A), which is closely related to the vaporisation temperature in the liquid–vapour equilibrium; moreover, the limiting corresponding partial molar properties allow us to estimate the boiling points of the pure components.     

Fluorometric Determination of Nitrogen Dioxide in Atmosphere Sampled by the Liquid Droplet Technique

A new, simple, sensitive and selective fluorometric method for the determination of nitrite has been developed. The reaction of nitrite with hydralazine in acidic medium, heated on a boiling water-bath for 15 min, produced a tetrazolo (5,1-a) phthalazine (Tetra-P). The product formed was measured at _ex = 274 nm and _em = 345 nm. The fluorescence intensity was valid over a nitrite concentration range 0.067–60.3 ng mL^–1, with a detection limit of 0.0091 ng mL^–1. The reproducibility of the proposed method was determined by running a different concentration of nitrite, 13.4, 33.5, and 46.9 ng mL^–1. The % recoveries and the relative standard deviations were found to be 100.6 ± 0.9, 99.9 ± 0.5, and 99.4 ± 1.1%, respectively. The proposed method was applied successfully to the determination of nitrogen dioxide sampled from the atmosphere using the liquid droplet method. The nitrogen dioxide our wind tunnel was controlled by an NO _x analyzer based on a chemiluminescence analyzer detector (CLAD 1000). A linear graph was obtained for the nitrogen dioxide in the wind tunnel vs. NO₂ sampled by the liquid droplet method. The effect of interference substances in the determination showed that cations and anions did not disturb the process. The results obtained were satisfactory when compared with the reference method.     

Development of silver-containing nanocellulosics for effective water disinfection

Electrospun cellulose nanofibers and cellulose-graft-polyacrylonitrile (Cell-g-PAN) copolymer nanofibers containing silver nanoparticles (AgNPs) were synthesized for effective water disinfection. Surface morphology, AgNPs content, physical distribution of AgNPs, levels of silver leaching from the fibers in water and antimicrobial efficacy were studied. Scanning electron microscope images revealed that AgNPs in cellulose nanofibers were more evenly dispersed than in Cell-g-PAN copolymer nanofibers, but with the certainty that Cell-g-PAN copolymer nanofibers had higher AgNPs content. This was confirmed by energy dispersive X-ray analysis and atomic absorption analysis. Both cellulose nanofibers and Cell-g-PAN copolymer nanofibers containing AgNPs had excellent antimicrobial activity against Escherichia coli, Salmonella typhi, and Staphylococcus aureus, with cellulose-nAg nanofibers killing between 91 and 99 % of bacteria in a contaminated water sample and Cell-g-PAN-nAg copolymer nanofibers killed 100 %. Neither Cell-g-PAN copolymer nanofibers nor cellulose nanofibers leached silver into water.     

Nanocomposite-based inorganic-organocatalyst Cu(II) complex and SiO2- and Fe3O4 nanoparticles as low-cost and efficient catalysts for aniline and 2-aminopyridine oxidation

Bis-imino Cu(II) complex (CuLAn₂), in which the imine ligand (HLAn) acts as a bidentate chelating ligand, was synthesized. The catalytic potential of the inorganic-organocatalyst was studied homogeneously and heterogeneously in the oxidation of aniline and 2-aminopyridine by H₂O₂ or tBuOOH. Two heterogeneous inorganic-organocatalysts, CuLAn₂@Fe₃O₄ and CuLAn₂@SiO₂@Fe₃O₄, were synthesized by the successful immobilization of CuLAn₂ on the Fe₃O₄ surface and the composited Fe₃O₄ with SiO₂, respectively. The heterogeneous structure of those inorganic-organocatalysts was confirmed using Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, and magnetic properties. The adsorption–desorption isotherms revealed respectable adsorption parameters (S_BET, V_p, and r_p). All catalysts exhibited high potential in the oxidation of aniline (with phenylhydroxylamine as the main product) and good potential in the oxidation of 2-aminopyridine, in the first attempt (with 2-nitropyridine-N-oxide and 2-nitrosopyridine-N-oxide as main products), at room temperature. Acetonitrile was found to be the best solvent compared to ethanol, dimethyl sulfoxide, chloroform, and water. The homogeneous catalyst exhibited reusability for three times. The heterogeneous catalysts, CuLAn₂@Fe₃O₄ and CuLAn₂@SiO₂@Fe₃O₄, were active for five and seven times, respectively. A mechanism was proposed within electron and oxygen transfer processes.     

A new germacranolide-type sesquiterpene lactone from Tanacetum santolinoides

A new germacranolide-type sesquiterpene lactone, 1alpha-hydroxy-3-oxo-7alpha,11betaH-germacra-4Z,9Z-dien-12,6alpha-olide (1), was isolated from the CH2Cl2--MeOH extract of the aerial parts of Tanacetum santolinoides. Its structure was determined by spectroscopic techniques including, IR, high-resolution-EIMS, and extensive 400 MHz one- and two-dimensional NMR-analysis (1H, 13C-NMR, DEPT, 1H--1H COSY, HMQC, HMBC, and NOE experiments).