Determination of polychlorinated biphenyls in biosolids using continuous ultrasound-assisted pressurized solvent extraction and gas chromatography-mass spectrometry

An efficient continuous pressurized solvent extraction (PSE) method assisted by ultrasound energy was developed for the extraction of polychlorinated biphenyls (PCBs) from biosolids. Analytes were determined in the extracts by gas chromatography-mass spectrometry in selected ion monitoring (SIM) mode. A screening-type experimental design pointing to dynamic extraction time as the only significant variable in the extraction process was carried out to optimize PCB extraction from the biosolids. Final selected conditions for PSE were extraction temperature, 50 degrees C; static extraction time, 0 min; and dynamic extraction time, 30 min. Recovery of the PSE method was 73%, which was significantly improved (103%) when PSE was assisted with 30-min ultrasound (US-PSE). Precision of the overall method, expressed as relative standard deviation, was 3.6% and the detection limit was 0.037 mg/kg. The method was applied to the determination of PCBs in biosolids from different water treatment plants from central Chile.     

Novel Studies about the Electrooxidation of a Deoxynivalenol (DON) Mycotoxin Reduction Product Adsorbed on Glassy Carbon and Carbon Paste Electrodes

A novel and fast square‐wave adsorptive anodic stripping voltammetric procedure on glassy carbon and carbon paste electrodes is described for the indirect trace quantitation of deoxynivalenol (DON) mycotoxin that frequently contaminates soya and foodstuff. The in situ homogeneous reduction of the toxin by product/s of dissolved oxygen electroreduction in pH 8 buffer solution makes the quantitation of DON possible through a simple electroanalytical technique. Moreover, its potential use for the analysis of real samples was demonstrated using a soya flour sample spiked with DON without previous separating procedures. The DON detection limits were 3.6 and about 6 ppb from standard solutions and soya flour matrix, respectively.     

alpha-arylation of ketones using highly active, air-stable (DtBPF)PdX2 (X = Cl, Br) catalysts

alpha-Arylation of various ketones with aryl chlorides and bromides using the well-defined and air-stable (DtBPF)PdX2 (X = Cl, Br) catalysts gave 80-100% yield of the coupled products under relatively mild conditions at low catalyst loadings. The X-ray structure of (DtBPF)PdCl2 revealed the largest P-Pd-P bite angle (104.2 degrees ) for a ferrocenyl bisphosphine ligand. 31P NMR monitoring of (DtBPF)PdCl2-catalyzed reaction of 4-chlorotoluene with propiophenone indicated that DtBPF remained coordinated in a bidentate mode during the catalytic cycle.     

Effects of natural environmental factors on delta13C of lichens

This preliminary study was designed to determine the extent to which the carbon isotope ratio in four species of lichens was influenced by such features as humidity, rainfall, radioactivity, and air quality. The sampling sites were selected to be at a great distance from any pollution. At the time of sampling, field data (temperature, relative humidity, average monthly precipitation, and radioactivity) were recorded. delta(13)C in whole lichen specimens were determined using standard mass spectrometric techniques with a standard deviation of+/-0.3 per thousand. We have found a weak but negative correlation between delta(13)C and relative humidity, and a positive correlation between delta(13)C and average monthly precipitation at the studied sites. The effects were minor, of the order of 1.5 per thousand for all the lichens. We have examined the correlation between (137)Cs activity concentration of the studied lichens and delta(13)C of these lichens, and we have suggested that fixation of radiocesium does not alter photosynthesis rate. There was a delta(13)C variation with the altitude gradient with less negative delta(13)C values at higher altitude. It is possible that this difference is caused by the ozone and occurred at the high elevations.     

Alcohols as electrophiles in C--C bond-forming reactions: the hydrogen autotransfer process

The hydrogen autotransfer process involves an initial oxidative hydrogen elimination, followed by different types of reactions, and is completed with a reductive hydrogen addition to give the final product. The sequence allows the alkylation of different nucleophilic agents using environmentally benign alcohols as electrophiles, mild conditions, and soft bases, with water produced as the only waste material. Recent examples of modulating the organometallic catalyst have also lent themselves to expansion of the range of available substrates, as described in this Minireview.     

1,3-Digermacyclobutanes with exocyclic C=P and C=P=S double bonds

New 1,3-digermacyclobutanes, with two exocyclic C=PMes* bonds, and the corresponding first bis(methylenethioxo)phosphoranes with C=P(S)Mes* moieties have been synthesized.     

Rare-earth based OLEDs

The improvement of operational lifetime and efficiency of organic light-emitting devices has stimulated many studies focused on the mechanisms responsible for their degradation. Such instabilities can be induced by several factors such as (i) current flow and heating, (ii) chemical reactions, (iii) self-conversion of the charge transporting molecules to cation, anion, and/or radical species. This work aims at investigating the thermal stability of rare-earth based tetrakis beta-diketonates complexes like M[Eu(dbm)₄] (M = Li⁺, TMPip⁺, and Morf⁺) through TG technique coupled with FTIR. Preliminary results show that Li[Eu(dbm)₄]·4H₂O complex presents no degradation in its structure until 300 °C. However, evidences of rapid thermal degradation of the other two compounds have been found at temperatures lower than 100 °C, implying that these complexes could be degraded during the thermal deposition process at relatively high temperatures.     

Polyhydrosilanes I. Synthesis

Abstract

Using the well known Wurtz coupling technique, polyhydrosilanes copolymers with diphenyl - and methyl(phenyl) - sequences, were synthesised. This work describes the possibility to maintain stable Si-H group and to obtain in good yields, soluble, high molecular, functional polysilanes. IR, ¹-NMR, ¹³C, UV spectral data, quantitative elemental Si and H (from Si-H) analyses and indirect molecular weight investigation sustain the molecular structure of the copolysilanes.     

Nonlinear Effects Related to the Simultaneous Excitation of Three Instabiities in Magnetized Plasma

Experimental results are presented on the nonlinear effects related to the simultaneous excitation of three low‐frequency instabilities in the magnetized plasma column of a Q‐machine, namely the potential relaxation instability, the electrostatic ion‐cyclotron instability and the Kelvin‐Helmholtz instability. The influence of electron drift and magnetic field intensity on appearance, dynamics and mutual interaction of these instabilities was investigated (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)