Copper(II)-8-hydroxquinoline coprecipitation system for preconcentration and separation of cobalt(II) and manganese(II) in real samples

A separation-preconcentration procedure based on the coprecipitation of cobalt(II) and manganese(II) ions with copper(II)-8-hydroxquinoline system has been developed. The analytical parameters including pH, amount of copper(II) as carrier element, amount of 8-hydroxquinoline, sample volume, etc., was investigated for the quantitative recoveries of Co(II) and Mn(II). No interferic effects were observed from the concomitant ions which are present in real samples. The detection limits for analyte ions by three sigma criteria were 0.86microgL(-1) for cobalt and 0.98microgL(-1) for manganese. The validation of the presented preconcentration procedure was performed by the analysis of NIST SRM 2711 Montana soil and GBW 07605 Tea certified reference materials. The procedure presented was applied to the analyte contents of real samples including natural waters and some food samples with successfully analytical results.     

Impact of H.I. Schlesinger's discoveries upon the course of modern chemistry on B−(N−)H hydrogen carriers

Representatives of B?(N?)H hydrogen carriers are alkali borohydrides (e.g. LiBH₄ and NaBH₄) and amine boranes (e.g. NH₃BH₃ and NaNH₂BH₃). These are old compounds; they were discovered in the first half of the 20th century. One of the main contributors to their development is Prof. Hermann I. Schlesinger (1882–1960). In the recent years, there has been new interest in these old compounds as novel chemical H storage materials. Sodium borohydride NaBH₄ is a typical example. It was discovered by Schlesinger and collaborators in the 1950s. At that time it was found to be an attractive H₂ generator; owing to this property it reemerged in the early 2000s for on-board H₂ generation. Today, Schlesinger is commonly considered as the pioneer of NaBH₄ as hydrogen carrier but the impact of Schlesinger and collaborators' discoveries upon the course of modern chemistry on B?(N?)H hydrogen carriers is far more extensive … This is highlighted herein.     

Bimetallic RuCo and RuCu catalysts supported on γ-Al2O3. A comparative study of their activity in hydrolysis of ammonia-borane

Bimetallic-based RuCo and RuCu catalysts, supported on γ-Al₂O₃ (1.5 wt% Ru as theoretical value), were synthesized by polyol method. Ru, Co, and Cu acetylacetonates were used as precursors and ethylene glycol as reducing agent. The as-synthesized catalysts were characterized by SEM, TEM, XRD and XPS, and tested in ammonia-borane (NH₃BH₃) hydrolytic dehydrogenation at variable amount of catalyst (10-30 wt%), concentration of NH₃BH₃ (1.0-0.65 M), and temperatures (50-65 °C). The reactions were monitored by volumetric (inverted burette) and spectroscopic methods (¹¹B and ¹¹B{¹H} NMR). It was found that the best bimetallic catalysts are those having a molar ratio Ru:Co and Ru:Cu of 1:1 such as RuCo > RuCu ∼ Ru. They, i.e. RuCo and RuCu, consist of nanosized spherical particles of Ru⁰Co(OH)₂ and Ru⁰Cu⁰, respectively. Kinetic investigation highlights similar rate laws with activation energies of 47 kJ mol⁻¹ and 52 kJ mol⁻¹, respectively, and, for both, reaction orders of 1 versus both the NH₃BH₃ and the catalytic free sites concentrations. ¹¹B and ¹¹B{¹H} NMR investigation confirmed (i) a more effective NH₃BH₃ hydrolytic dehydrogenation in the presence of RuCo catalyst even though a loss of activity after the first run was observed for both catalysts, and (ii) a rapid NH₃BH₃ hydrolysis with initial formation of B(OH)₄⁻, which besides favors equilibriums of formation of polyborates. These results are reported and the reaction mechanism discussed herein.     

Inactivation of Listeria monocytogenes on Unpackaged and Vacuum-Packaged Chicken Frankfurters Using Pulsed UV-Light

ABSTRACT:  The effectiveness of pulsed UV-light on the microbial load and quality of unpackaged and vacuum-packaged chicken frankfurters was investigated. Samples were inoculated with  Listeria monocytogenes  Scott A on the top surfaces, and then treated with pulsed UV-light for 5, 15, 30, 45, and 60 s at 5, 8, and 13 cm distance from the quartz window in a pulsed UV-light chamber. Log reductions (CFU/cm²) on unpackaged samples were between 0.3 and 1.9 after 5-s treatment at 13 cm and 60-s treatment at 5 cm, respectively. Log reductions on packaged samples ranged from 0.1 to 1.9 after 5-s treatment at 13 cm and 60-s treatment at 5 cm, respectively. The temperature changes of samples and total energy (J/cm²) received at each treatment condition were monitored. The extent of lipid peroxidation and the color were determined by thiobarbituric acid-reactive substances (TBARS) test and CIELAB color method, respectively. Lipid peroxidation of samples did not change significantly ( P  > 0.05) after mild (5-s treatment at 13 cm) and moderate (30-s treatment at 8 cm) treatments. Significant differences ( P  < 0.05) in color parameters were observed after treatments of both unpackaged and packaged samples. Packaging material was also analyzed for mechanical properties. The elastic modulus, yield strength, percent elongation at yield point, maximum tensile strength, and percent elongation at break did not change significantly ( P  > 0.05) after mild treatment. Overall, this study demonstrated that pulsed UV-light has a potential to decontaminate ready-to-eat (RTE) poultry-based food products.     

RAFT-mediated synthesis of cationic poly[(ar-vinylbenzyl)trimethylammonium chloride] brushes for quantitative DNA immobilization

The synthesis of cationic poly[(ar-vinylbenzyl)trimethylammonium chloride)] [poly(VBTAC)] brushes was achieved via reversible addition-fragmentation chain transfer (RAFT) polymerization and used for quantitative DNA immobilization. Initially, silicon surfaces were modified with RAFT chain transfer agent by utilizing an amide reaction involving a silicon wafer modified with allylamine and 4-cyanopentanoic acid dithiobenzoate (CPAD). Poly(VBTAC) brushes were then prepared via RAFT-mediated polymerization from the surface immobilized CPAD. Various characterization techniques including ellipsometry, X-ray photoelectron spectroscopy, grazing angle-Fourier transform infrared spectroscopy, atomic force microscopy and contact-angle goniometer were used to characterize the immobilization of CPAD on the silicon wafer and the subsequent polymer formation. The addition of free CPAD was required for the formation of well-defined polymer brushes, which subsequently resulted in the presence of free polymer chains in solution. The free polymer chains were isolated and used to estimate the molecular weights and polydispersity index of chains attached to the surface. Moreover, from atomic force microscopy and ellipsometry measurements, it was also determined that the density of immobilized DNA on the cationic poly(VBTAC) brushes can be quantitatively controlled by adjusting the solution concentration.     

Efficacy of aqueous ozone for the decontamination of Escherichia coli O157:H7 and Salmonella on raspberries and strawberries

The efficacy of ozone as a water additive for washing raspberries and strawberries was investigated. Pathogen-inoculated fruits were treated with aqueous ozone concentrations of 1.7 to 8.9 mg/liter at 20 degrees C for 2 to 64 min, with an aqueous ozone concentration of 21 mg/liter at 4 degrees C for 64 min, or with water as a control. Maximum pathogen reductions on raspberries were 5.6 and 4.5 log CFU/g for Escherichia coli O157:H7 and Salmonella, respectively, at 4 degrees C, whereas reductions on strawberries were 2.9 and 3.3 log CFU/g for E. coli O157:H7 and Salmonella, respectively, at 20 degrees C after 64 min. Washing with water (sparging with air as control) resulted in reductions of approximately 1 log CFU/g. The results presented here indicate that aqueous ozone may be useful as a decontaminant for small fruits.     

Analysis of rate-dependent tensile properties of polypropylene fibres used in thermally bonded nonwovens

The stress–strain behaviour of polypropylene fibres is evaluated for various tensile strain rates. Fibre samples are extracted from a thermally bonded nonwoven and fixed in a low-load tensile test machine. A methodology is introduced to implement a constant true strain rate at high strain tests for conventional tensile test machines. The obtained results indicate that polypropylene fibres show a highly viscous behaviour, especially during the initial stage of load application. No significant difference in a tensile behaviour of fibres was observed for loading regimes with a constant true strain rate and a constant engineering strain rate.