Thermal stability of acrylonitrile/chlorosulphonated polyethylene rubber blend

The properties of chlorosulphonated polyethylene (CSM) rubber, acrylonitrile rubber (NBR) and their blend (50/50 w/w) were studied. Fourier transform infrared (FTIR) studies supported that CSM/NBR rubber blend is self curable, when cross-linking takes place between acrylonitrile groups of NBR and –SO₂Cl groups or in situ generated allyl chloride moieties of CSM. The thermal stability of vulcanizates was analyzed in nitrogen by thermogravimetry. It was found that the initial degradation temperature of elastomer based on CSM rubber is lower than of pure NBR rubber. By adding NBR to CSM rubbers, the degradation temperature of crosslinked material increased, indicating higher thermal stability. The activation energy for the degradation are determined using the Arrhenius equation The activation energies for the rubber blends are higher than for elastomers based on pure rubbers. It was found that the mass loss of the blends at any temperature was between those of the pure rubbers. The differential scanning calorimetry (DSC) was used for the glass transition temperature determination. It is estimated thermodynamic immiscibility of NBR/CSM blend based on noticed two different glass transition temperatures, corresponding to CSM and NBR rubbers.     

catena‐Poly[[tetra­kis(μ‐propionato‐κ2O:O′)dicopper(II)]‐μ‐3‐pyridylmethanol‐κ2N:O‐[bis­(propionato‐κO)bis­(3‐pyridylmethanol‐κN)copper(II)]‐μ‐3‐pyridylmethanol‐κO:N]

The title compound, [Cu₃(C₃H₅O₂)₆(C₆H₇NO)₄]_n, is composed of polymeric chains formed by alternating centrosymmetric Cu₂(μ‐CH₃CH₂CO₂)₄ and Cu(C₃H₅O₂)₂(C₆H₇NO)₂ units. These elemental units are linked by two bridging 3‐pyridylmethanol (3PM) ligands. The Cu₂(μ‐CH₃CH₂CO₂)₄ group presents a centrosymmetric tetra­bridged structure with four syn–syn bridging propionate ligands to which two 3PM mol­ecules are bonded (through N), occupying the apical positions of each square‐pyramidal polyhedron around the Cu^II ions. The remaining mononuclear group is centred around a third Cu^II ion, which lies on a symmetry centre and is bound to two monodentate propionate groups (through O), two monodentate 3PM mol­ecules (through N) and two bridging 3PM mol­ecules (through O), thus completing a square‐bipyramidal CuO₂N₂O₂ coordination.     

Carbon‐Based Electrodes for Sensitive Electroanalytical Determination of Aminonaphthalenes

The electroanalytical performance of bare glassy carbon electrodes (GCE) for the determination of 1‐aminonaphthalene (1‐AN) and 2‐aminonaphthalene (2‐AN) was compared with GCE modified by a Nafion permselective membrane or multiwalled carbon nanotubes and with other types of carbon‐based materials, carbon film and boron doped diamond. Nafion‐modified GCE gave the highest sensitivity and lowest detection limit (0.4 µmol L^?1) for differential pulse voltammetric determination of 1‐AN. Electrochemical impedance spectroscopy gave information about the processes at the electrode surface. Simultaneous determination of 1‐AN and 2‐AN in a mixture at GCE and their determination in model samples of river water is presented.     

Comparison of different approaches to the statistical evaluation of proficiency tests

The objective of this study was to compare different z-score calculation for the results from proficiency testing programmes. The comparison was carried out on the data from proficiency tests for four different matrices and for all analytes included in the proficiency testing programmes organised by UKZUZ institute from the year 2005 to 2007. It represented 99 samples (three periods per year and eleven samples distributed in each period); the number of determined analytes was 108 in each period. The total number of investigated data sets was 953. Three different approaches to z-score calculation were compared. The results gave reasonably comparable evaluation in most cases but sometimes UKZUZ method proved to be rather strict. The procedure using the robust average and robust standard deviation calculated according to Algorithm A described in ISO 13528 was found to be the most suitable for matrices and level of measurands in UKZUZ proficiency tests.     

Synthesis and Characterisation of a New Schiff‐Base‐like Ligand and its Iron(II) Complexes

The reaction of iron(II) acetate with the tetradentate Schiff base like ligand H₂L [(E,E)‐[{diethyl 2,2’‐[4,5‐dihydroxy‐1,2‐phenylenebis(iminomethylidyne)]bis3‐oxobutanato}]) leads to the formation of the octahedral N₂O₄ coordinated complex [FeL(MeOH)₂] · MeOH ( 1 ). Conversion of 1 with N‐methylimidazole (N‐meim) leads to the N₄O₂ coordinated complex [FeL(N‐meim)₂] · MeOH ( 2 ). Both complexes are pure HS compounds that were characterised using magnetic measurements and X‐ray crystallography. A special attention was given to the role of the two hydroxyl groups at the phenyl ring on the formation of a hydrogen bond network and the influence of this network on the magnetic properties.     

Vapour-liquid equilibrium in the acetone-water system at 101.325 kPa

Vapour-liquid equilibrium in the title system was measured with special regard to concentration limits. The data of both regions were fitted to six different equations for the determination of the best values of limiting activity coefficients (11.53 and 5.58 for acetone and water, respectively). The densities of solutions at 25°C were determined in both boundary regions.     

Sensitive GC/MS determination of 15 isomers of chlorobenzoic acids in accelerated solvent extracts of soils historically contaminated with PCBs and validation of the entire method

Chlorobenzoic acids (CBAs) are the major metabolite of aerobic bacterial degradation of polychlorinated biphenyls (PCBs). A rapid and simple simultaneous derivatisation method has been developed for gas chromatography-mass spectrometry determination in historically PCB-contaminated soils for 15 isomers of mono-, di-, tri-, tetra-, and pentachlorobenzoic acids in CBA mixtures. Two derivatisation agents (diazomethane and methyl chloroformate) and various conditions were evaluated (temperature, time, solvents, catalysts) in terms of efficiency. The optimised derivatisation method with diazomethane and 1% methanol running 1 hour at 5°C was used for derivatisation of extracts of soils and river sediment from historically PCB-contaminated sites; the extracts were prepared using accelerated solvent extraction by a previously described method. Methylated CBAs were separated by gas chromatography using a system with two different common columns, DB-5 and DB-200, in series-coupled (tandem) arrangement and detected by EI-MS. A clean-up with a gel permeation chromatography was carried out to remove soil interfering matrix compounds as well as major portion of PCBs. The limits of quantification ranged between 1 and 10 ng g^?1 of individual CBA in the soil. The procedure was applied to various soil samples from Lhenice (Czech Republic) highly contaminated with PCBs. CBAs were found in all tested soils and also in the river sediment. The most contaminated soil contained all CBAs representatives under the study with a total concentration of 3.1 µg g^?1 of dry soil.     

Thermal properties and morphology of cassava starch grafted with different content of polystyrene

The interest in replacing synthetic polymers by biodegradable materials from renewable resources is steadily increasing. In this work, cassava starch grafted with different content of polystyrene (PS) was synthesized via free-radical polymerization using suspension polymerization technique. Thermal data of pure starch and the grafted starch with different content of PS were collected by simultaneous thermogravimetric (TG)–differential scanning calorimetry (DSC) setup in open alumina pans. Separately, typical DSC measurements were conducted in standard aluminum pans with lid. The data obtained by different methods are correlated and discussed. Morphology of cryogenic fracture surface of starch sample was studied by scanning electron microscopy. In order to obtain more reliable data about the processes taking place during the thermal treatment, the changes of surface morphology of starch treated at different temperatures are observed.     

Tubular and Microcylindrical Platinum Electrodes for Amperometric Detection of Aminobiphenyls and Aminonaphthalenes in HPLC

Platinum electrodes in microcylindrical and tubular arrangements were compared as working electrodes for amperometric detection of 2‐aminobiphenyl, 4‐aminobiphenyl, 1‐aminonaphthalene, and 2‐aminonaphthalene in HPLC. Factors influencing separation efficiency are favourable for microcylindrical arrangement while tubular arrangement exhibits higher sensitivities and lower limits of detection. These are in the range of 0.0078–0.027 µmol L^?1 for tubular, and 0.11–0.42 µmol L^?1 for microcylindrical arrangement. Further, a new method with nanomolar detection limits was proposed for determination of tested compounds in urine using solid phase extraction for preliminary separation and preconcentration of the analytes.