Chemometric interpretation of pesticide occurence in soil samples from an intensive horticulture area in north Portugal

An extensive monitoring programme of pesticides was carried out in soil samples from an intensive horticulture area in north of Portugal, putting into practice the needs for increased control of soil quality as far as organic pollution is concerned. The area under investigation was additionally defined as vulnerable to nitrates due to local soil and aquifer characteristics, which might be extended to pesticides contamination. Five sampling sites were selected and soils analysed at three depths in eight sampling campaigns, for the period of 2 years. A stepwise multivariate statistical approach was selected to uncover most relevant patterns inside a complex environmental data matrix. Cluster analysis was applied both to group pesticides and samples, giving a primary and unsupervised overlook of privileged relationships. Clusters of persistent pesticides and selected herbicides were identified, whereas sample classes were also formed and disposed geographically. Thirty eight percent of analysed soils samples fell into one class characterized by low contamination (class 1 in cluster analysis), which is entirely representative of the sampling site no. 1. Afterwards, linear discriminant analysis was applied to identify those pesticides, which had a higher impact in the definition of classes. Finally, factor analysis using a five component model was implemented in order to bring to light the constitution and data variance explained by each of the five main principal components, as well as, their relation to pest management practices. A factor was identified (PC1 – 22% variance) composed of chlorinated pesticides, which was representative of one of the investigated sites indicating its high contamination status. Qualitative main findings and class average concentration values were obtained through this multivariate statistical approach.     

Transuranic elements alpha-particle energy analysis using nuclear track in solids methodology

This paper presents a method for the energy analysis of alpha-particles emitted by transuranic elements via a novel technique using Nuclear Tracks. The method is based on the relationship between the energy deposited in the detection material and the diameter of the track, that is formed by chemical etching. The method involves CR-39 polycarbonate as the detector material, one-step chemical etching after irradiation, and a digital image analysis system for automatic reading of the track diameters. The experimental study included alpha-particles in the energy range 5.1 MeV to 5.8 MeV emitted by²³⁹Pu,²⁴¹Am and²⁴⁴Cm. The quantitative results provide a clear signature to identify each one of the emitters based on a characteristic track diameter.     

A short and efficient enantioselective route to a key intermediate for the total synthesis of forskolin

A simple route for the enantioselective synthesis of key intermediates (11 and 12) for the total synthesis of forskolin has been developed starting from acid 6 and (S)-alcohol 5. The latter is prepared by enantioselective catalytic CBS reduction of dienone 3, and is converted by an intramolecular Diels-Alder reaction to tricyclic lactone 9.     

The effects of cationic and zwitterionic micelles on the keto-enol interconversion of 2-phenylacetylfuran and 2-phenylacetylthiophene

The presence of micelles from cationic and zwitterionic surfactants increases the apparent acidity of either the keto and the enol forms of 2-phenylacetylfuran (2PAF) and 2-phenylacetylthiophene (2PAT). This effect can be attributed to the affinity of the surfactant micelles for the enolate of the two substrates. Although the equilibrium constants for keto-enol tautomerism of 2PAF and 2PAT, K_T=[enol]/[ketone]=pK_a^KH−pK_a^EH, do not change much, the presence of micelles provides an efficient method for producing appreciable quantities of the enolates under mild experimental conditions and in aqueous solutions. The obtained rate-profiles for the ketonisation reactions and the consistency of the kinetic rate constants over a wide range of ‘pH’ in several overlapping buffers indicate that the pH of the aqueous pseudophase (but not that at the micellar surface) can be controlled by buffers. Moreover, the increase of the acidity and the decrease of the ‘water’ rate of ketonisation of the enols of 2PAF and 2PAT upon addition of surfactants allow the uncovery of a metal ion catalysed pathway that cannot be observed in absence of surfactants.     

A more convenient and general procedure for O-monobenzylation of diols via stannylenes: a critical reevaluation of the Bu2SnO method

A more consistent, straightforward, and economical protocol for generation of stannylene species and their reaction with BnBr leading to products of O-monobenzylation of diols has been set. It has shown to be specially indicated for substrates bearing vicinal trans 1,2-diol moieties on cyclohexane backbones, which are more resistant to these transformations. Such protocol has been successfully applied to myo-inositol derivatives and acyclic diols.     

Selective determination of copper with pyridoin phenylhydrazone as chromogenic extraction reagent

Summary The synthesis, characteristics and analytical applications of pyridoin phenylhydrazone are described. It reacts with copper(I) to produce an orange 11 complex ( _max=450 nm,=2.1×10⁴l· mole^–1·cm^–1) in aqueous ethanolic solution; it behaves as a cuproin type reagent. The orange complex can be extracted into amyl alcohol ( _max=440 nm,=2.0×10⁴l·mole^–1·cm^–1), and used for the spectrophotometric determination of trace amounts of copper. Interferences have been investigated.

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Zusammenfassung Synthese, Eigenschaften und analytische Anwendung von Pyridoin-phenylhydrazon wurden beschrieben. Es reagiert mit Cu(I) unter Bildung eines orange gefärbten 11-Komplexes in wäßrig-alkoholischer Lösung ( _max=450 nm,=2,1×10⁴l·mol^–1·cm^–1); das Reagens verhält sich ähnlich wie Cuproin. Der erwähnte Komplex läßt sich mit Amylalkohol extra-hieren ( _max=440 nm,=2,0×10⁴l·mol^–1·cm^–1) und zur spektrophoto-metrischen Bestimmung von Kupferspuren benützen. Auftretende Störungen wurden angegeben.

     

A new production method for carrier-free201Tl using IEN'S cyclotron in Rio De Janeiro

A new and simplified method was developed for the separation of thallium 201 which will allow the shipment of a “one shot generator” to distant places and easy elution at the destination. Thallium is produced as usually, through the reaction $${}^{nat}Tl/p,xn/^{201} pb\xrightarrow{{\beta ^ + }}{}^{201}Tl$$ with 24-MeV protons from IEN'S CV-28 cyclotron. The separation is based on the properties of a chelating carboxylic acid cation exchange resin column which at pH 4.5 retains lead while thallim is easily eluted. This column can also be used as a regular generator to produced greater quantities of²⁰¹Tl but at the expense of more elutions.     

3β‐(Stearyloxy)olean‐12‐ene from Austroplenckia populnea: Structure Elucidation by 2D‐NMR and Quantitative 13C‐NMR Spectroscopy

3β‐(Stearyloxy)olean‐12‐ene was isolated from a hexane extract of Austroplenckia populnea Reiss (Celastraceae) leaves. The structure was solved by means of quantitative ¹³C‐NMR, HMBC, HMQC, COSY, NOESY, and NOE difference spectra. The mass spectrum showed an [M+1]⁺ ion peak at m/z 693, and the molecular formula C₄₈H₈₄O₂ was confirmed by combustion analysis.     

Theoretical study of p‐methacryloyl‐aminophenylarsonic acid

Conformations of p‐methacryloylaminophenylarsonic acid (p‐MAPHA) are determined through molecular mechanics and DFT/B3LYP calculations. Solvation effects are studied within the self‐consistent isodensity continuum model (SCI‐PCM). The stationary points were found to correspond to minima as verified by the analysis of vibrational frequencies in the molecule. The molecular optical absorption was obtained by using different solvent environments. The present results are in good agreement with the available experimental data. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Long-term diffusive samplers for the indoor air quality evaluation

Three kinds of diffusion samplers, conceived to perform long-term samplings in indoor sites are illustrated in this work. Two of them, in part deriving from the previous "Analyst for VOC" device, extend the field of application up to the semi-volatile organic compounds (SVOC), PAHs and nicotine in particular. A third device, which employs a basic barium hydroxide solution as an absorbing medium, is proposed for the determination of carbon dioxide levels which indicate the air change quality in the indoor sites. Laboratory and field experiments, performed in order to assess the reliability of the proposed devices, are shown. A monthly monitoring campaign, performed at three private apartments in Rome and its outskirts highlights that the indoor pollution levels are a complex function of various concurrent and opposite factors, like external air pollution, internal sources, air change rate and sink effect of surfaces, which contribute to depletion phenomena through adsorption and/or decomposition processes.