Properties of well‐defined alternating and random copolymers of methacrylates and styrene prepared by controlled/living radical polymerization

The physical properties of well‐defined alternating copolymers poly(methyl methacrylate‐alt‐styrene) and poly(n‐butyl methacrylate‐alt‐styrene), prepared by reversible addition–fragmentation chain transfer polymerization in the presence of Lewis acids, were investigated with differential scanning calorimetry, wide‐angle X‐ray scattering, and dynamic mechanical measurements. The properties were compared with those of random copolymers of the same overall composition and the corresponding homopolymers. Wide‐angle X‐ray scattering data showed that the alternating copolymers possessed a more regular comonomer sequence than the random copolymers. The thermomechanical properties of alternating copolymers and random copolymers were quite similar and typical for amorphous polymers, but in one of the cases studied the glass‐transition temperature for alternating copolymer was remarkably higher than for the random copolymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3440–3446, 2005     

Sampling and analysis of rain: methods and results of the Venice regional network

Summary Air quality and in particular acid rain composition has gained a great importance in the recent years all over the world. A vast research program has been undertaken also in the Venice Region. A network of 8 sampling stations, remote from motor traffic and industrial sources of air pollutants, was realized in 1988 according to the EMEP statements. It gives meteorological and physical data on the air quality and produces the wet-only samples of meteorological precipitations, of which the chemical composition is determined in laboratory. An automatic analyzer based on colorimetric methods is used for ammonium, sulfate, nitrate, phosphate and chloride determination and an Atomic Absorption spectrometer for Ca, Mg, K and Na analysis. The methods used are based on those recommended by U.S. Standard Methods for water samples. From all of them the method for sulfate determination needed the most serious modifications, due to the interferences of cations. This paper describes the analytical methods used and their detection limits. Data on the rain quality of the region, in the period February–June 1989 for the first 6 stations installed are reported together with their statistical elaborations. The relationships between single ions and the total amount of ions allow to interpret the rain water composition and to check the validity of the analytical methods. The average rain composition approximates a H₂SO₄/HNO₃ mixture with a volume-weighted average of pH of 5.42 and SO ₄ ^2– /NO ₃ ^– molar ratio of 1.10.     

Dynamic mechanical properties of epoxy/novolac system modified with reactive liquid rubber and carbon filler

This paper reports on the work carried out to evaluate the frequency dependent viscoelastic properties of epoxy/novolac compositons modified with a liquid reactive rubber and carbon filler. For epoxy systems modified with elastomer, three typical transitions were observed: the α-relaxation deeply related to the glass transition of epoxy, the β-transition of epoxy, and the glass transition of rubber appeared near to the β-relaxation of epoxy resin. Considering an Arrhenius equation, the activation energies of β-relaxation were estimated. In the region of glass transition and rubbery state the temperature dependence of the shift factor (α_T) was determined through Williams-Landel-Ferry (WLF) equation.     

Determination (monitoring) of PAHs in surface waters: why an operationally defined procedure is needed

The results of interlaboratory studies on the determination of selected PAHs in samples of pure water and water containing suspended matter are presented and discussed in this study. Determinations were performed by independent analytical laboratories which used different sample-preparation procedures, i.e. liquid-liquid extraction and solid-phase extraction with columns and speedisks. The study indicates that the results of PAHs determination depend on the type of isolation technique and the final determination procedure used by a given laboratory. Differences among the determined concentrations of specific PAHs reached 700%. In this work it has been shown that modern analysis does not offer isolation techniques for PAHs which would secure their speciation in the aquatic environment.     

Drastically decreased reactivity of thiols and disulfides complexed by cucurbit[6]uril

The cucurbit[6]uril (CB6) host forms stable complexes with 2-aminoethanethiol (cysteamine) and a derivative that contains a bulky terminal group attached to the amine group, as well as with the related disulfide cystamine. In these complexes, the thiol or the disulfide group is encapsulated inside the host cavity. The CB6-complexed thiols show drastically decreased reactivity with several oxidants, while the CB6-bound disulfide also exhibits hindered reactivity with reducing agents, such as dithiothreitol.     

Determination of Abamectin Residues in Avocados by Microwave-Assisted Extraction and HPLC with Fluorescence Detection

In this article a new analytical method for the confirmation and quantification of abamectin residues in avocados is described. The method allows a fast analysis of abamectin homologues using microwave assisted extraction (MAE), solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with fluorescence (FL) detection using trifluoroacetic anhydride (TFAA) and N-methylimidazole (NMIM) as derivatizing agents. The mobile phase consisted of water, methanol and acetonitrile (5:47.5:47.5 v/v/v) and was pumped at a rate of 1.1 mL min⁻¹ (isocratic elution). Homogenized avocado samples were extracted once with 20 mL acetonitrile:water 4:1 (v/v) in a microwave oven for 26 min at 700 W with a maximum temperature of 80 °C. MAE operational parameters were optimized by means of an experimental design. Extracts were cleaned using C₁₈ SPE cartridges. Average recoveries of the method at four spiked levels (0.005, 0.01, 0.10 and 1.0 mg kg⁻¹) were found to be in the range 90–100% with good precision (RSD < 12%). The limits of detection (LODs) and quantification (LOQs) of the whole method were 0.001 and 0.003 mg kg⁻¹, respectively, which are lower than the maximum residue limit (MRL) established by the Spanish and the European legislation in avocados (0.01 mg kg⁻¹). Several avocado samples previously treated with the pesticide were also analyzed.     

MLC Determination of Preservatives in Cranberry Foodstuffs

Optimized conditions for the determination of 14 food preservatives were selected by using interpretative optimization strategy and Derringer’s desirability function for combining three main chromatographic goals: resolution, separation time and ruggedness. The best mobile phase for separation by micellar liquid chromatography contains 0.045 M SDS and 1.0% (v/v) 1-pentanol at pH 2.5 adjusted with trichloroacetic acid. The accuracy of the method was confirmed by analysis of spiked samples and is useful for routine analysis of food preservatives in drinks due to simple sample preparation, safety and low cost of micellar mobile phases. Presented in part by A.P. Boichenko at the 4th Black Sea Basin Conference on Analytical Chemistry, 19–23 September, 2007, Sunny Beach, Bulgaria.     

Synthesis, characterization, and sorption properties of amorphous titanium phosphate and silica-modified titanium phosphates

Amorphous titanium hydroxyphosphate with formula Ti(OH)(1.36)(HPO(4))(1.32).2.3H(2)O and a new silica-modified titanium hydroxyphosphate with a general formula Ti(OH)(2x)(HPO(4))(2-x).ySiO(2).nH(2)O are synthesized and characterized using IR, TG, XRD, SEM, solid-state NMR, and BET techniques. It is concluded that SiO(2) is evenly distributed within the titanium phosphate (TiP) agglomerates and that neither the separate silica phase nor the titanium silicates are formed during the synthesis of silica-modified titanium hydroxyphosphate. Correlations between the texture, ion-exchange properties of the amorphous titanium hydroxyphosphate, and the amount of SiO(2) present within the TiP matrix are established. Sorption properties of silica-modified titanium hydroxyphosphate toward Cs(+) and Sr(2+) are studied in a series of samples with an increasing amount of silica, at different pH, and in NaCl solutions with a varying ionic strength. It is found that sorption of Cs(+) does not depend practically on the amount of SiO(2) present, whereas the Sr(2+) uptake drastically decreases with an increase of silica amount. The effects of pH and of the electrolyte concentration on the sorption behavior of titanium phosphate are discussed in terms of ionic hydration shell and titanium phosphate structural specificity. The kinetics of sorption processes is also investigated, and the diffusion coefficients for cesium and strontium are obtained.     

An easy microwave-assisted synthesis of sulfonamides directly from sulfonic acids

An easy and handy synthesis of sulfonamides directly from sulfonic acids or its sodium salts is reported. The reaction is performed under microwave irradiation, has shown a good functional group tolerance, and is high yielding.     

Wetting films on a hydrophilic silica surface obtained from aqueous solutions of hydrophobically modified inulin polymeric surfactant

The thickness of wetting films on a hydrophilic silica surface was investigated using a microinterferometric technique. Aqueous solutions of hydrophobically modified inulin (INUTEC^®SP1) at various concentrations, in the presence or absence of NaCl or Na₂SO₄, were studied. The equilibrium film thickness (h _eq) showed a complex dependence on INUTEC^®SP1 concentration. At low electrolyte concentrations, h _eq decreased with an increase in INUTEC^®SP1 concentration, reaching a minimum at 10^?6 mol dm^?3. However, at high electrolyte concentrations, this dependence became less pronounced. At any given INUTEC^®SP1 concentration, the equilibrium film thickness decreased with an increase in electrolyte concentration as a result of the compression of the electrical double layer reaching a minimum value. After that, the film thickness showed a small decrease with further increase in electrolyte concentration. This indicates that the electrostatic component of disjoining pressure can be neglected, and the steric repulsion of the loops and tails of INUTEC^®SP1 determined the film thickness.