Secondary ion mass spectrometry and alpha-spectrometry of electrodeposited thorium films

The main aim of this work was the preparation of samples with thorium content on the steel discs by electrodeposition for determination of natural thorium isotope by alpha spectrometry and secondary ion mass spectrometry and finding out their possible linear correlation between these methods. The analysis of the composition of surface was other aim of study. Discs were measured by alpha spectrometer. After that, alpha spectrometry discs were analyzed by TOF-SIMS IV, which is installed in the International Laser Centre in Bratislava. The integral and normalized intensities of isotope of ²³²Th and intensities of ions of ThO⁺, ThOH⁺, ThO₂H⁺, Th₂O₄H⁺, ThO₂ ^?, ThO₃H^?, ThH₃O₃ ^? a ThN₂O₅H^? were measured. The linear correlation is between surface’s weights of Th and intensities of ions of Th⁺ from identified in SIMS spectra. We found out the chemical binding between thorium and oxygen and hydrogen on the surface of samples by SIMS method. Obtained intensities of ions ²³²ThO⁺, ²³²ThOH⁺, ²³²ThO₂H⁺ prove the presence of oxidized forms of thorium in the upper layers of surface. The oxidized ions predominate in univalent form of thorium up to deep about 3,000 nm.     

Asymmetric Nucleophilic Monofluorobenzylation of Carbonyl Compounds: Synthesis of Enantiopure vic‐Fluorohydrins and α‐Fluorobenzylketones

Asymmetric nucleophilic monofluoroalkylation of a broad range of aldehydes with an α‐fluoro‐γ‐sulfinylbenzyl carbanion takes place with complete control of the facial selectivity at the carbanion and good to high anti‐diastereoselectivity to give easily separable mixtures of two optically pure 1,2‐fluorohydrin derivatives (up to 24:1 anti/syn). Separation and removal of the p‐tolylsulfinyl group with tBuLi provides enantiomerically pure anti‐1,2‐disubstituted‐1,2‐fluorohydrins, whereas α‐fluorobenzylketones can be obtained by desulfinylation of the mixture followed by pyridinium chlorochromate oxidation (one‐pot process).     

Thermal properties of solid complexes with biologically important heterocyclic ligands

Thermogravimetry (TG), derivative thermogravimetry (DTG) and infrared (IR) spectroscopy have been applied to the investigation of the thermal behaviour and structure of the compounds [Cu(2-Clbz)₂(nia)₂(H₂O)₂] (I), [Cu(2-Clbz)₂(nia)₂]·H₂O (II), [Cu(2-Brbz)₂(nia)₂]·2H₂O (III), [Cu(2-Brbz)₂(nia)₂(H₂O)] (IV), where 2-Clbz and 2-Brbz?=?2-chloro- and 2-bromobenzoate anions, nia?=?nicotinamide, H₂O?=?water molecules. Thermal decomposition of all studied compounds proceeds in three steps. Heating the compounds first results in a release of non-coordinated and/or coordinated water molecules. The final product of thermal decomposition was CuO. The thermal stability of the complexes can be ordered in the sequence: I<IV<III<II. Nicotinamide is coordinated to Cu(II) through the nitrogen atom of the heterocyclic ring. IR data suggest the unidentate coordination of benzoate anions to Cu(II) in complexes I, IV and bidentate coordination in complexes II and III.     

Effect of Low Temperature Air Plasma Treatment on Wetting and Flow Properties of Kaolinite Powders

It was found in this study that the air plasma treatment of particular kaolinite has led to the change of its wettability, which was reflected in the decreased values of water contact angles of wetting from 88.7° for virgin kaolinite to 86.3° for 30?min air plasma treated one. Plasma treated samples show higher average surface energies in the wide range of coverage regimes in comparison to the virgin samples as determined by inverse gas chromatography. Results of these measurements confirmed our assumption, that air plasma treatment activates surface energy of the crystal planes of the kaolinite as reflected in the broadened dispersive surface energy distribution after 10?min treatment time. However with prolonged 30?min treatment time the dispersive surface energy distribution profile was decreased. We assume, that the latter decrease reflects the distorsion of the crystal lattice of the kaolinite as confirmed by FTIR analysis as reflected in changes of Si?CO?CSi and Al₂O?CH characteristic absorption bands. Calculated dispersive surface free energy for 24?% surface coverage was increased from original 35?mJ/m² to 40.3 and 40.8?mJ/m² for 10 and 30?min treatment times. There were determined yield locus and flow function dependencies at different stress levels for virgin and different time plasma treated samples (flow index??ff _c , effective angle of internal friction???? _e , unconfined yield strength???? _c ). It was found that by plasma treatment the character of the flow was shifting from region of very cohesive (ff _c ?=?2.39) to the cohesive (ff _c ?=?3.19). For untreated samples effective angle of internal friction was decreased with increasing applied consolidation stress, while for plasma treated kaolinite it was increased.     

Laccase-Mediated Transformations of Endocrine Disrupting Chemicals Abolish Binding Affinities to Estrogen Receptors and Their Estrogenic Activity in Zebrafish

Endocrine disrupting chemicals (EDCs) are known to mainly affect aquatic organisms, producing negative effects in aquaculture. Transformation of the estrogenic compounds 17??-estradiol (E2), bisphenol-A (BPA), nonylphenol (NP), and triclosan (TCS) by laccase of Coriolopsis gallica was studied. Laccase is able to efficiently transform them into polymers. The estrogenic activity of the EDCs and their laccase transformation products was evaluated in vitro as their affinity for the human estrogen receptor alpha (hER??) and for the ligand binding domain of zebrafish (Danio rerio) estrogen receptor alpha (zfER??LBD). E2, BPA, NP, and TCS showed higher affinity for the zfER??LBD than for hER??. After laccase treatment, no affinity was found, except a marginal affinity of E2 products for the zfER??LBD. Endocrine disruption studies in vivo on zebrafish were performed using the induction of vitellogenin 1 as a biomarker (VTG1 mRNA levels). The use of enzymatic bioreactors, containing immobilized laccase, efficiently eliminates the endocrine activity of BPA and TCS, and significantly reduces the effects of E2. The potential use of enzymatic reactors to eliminate the endocrine activity of EDCs in supply water for aquaculture is discussed.     

A new phenanthrene-based bis-oxime chemosensor for Fe(III) and Cr(III) discrimination

The synthesis of two new 2,7-disubstituted phenanthrene-based bis oximes is described. The ability of these two compound for complexing heavy metal cations have been studied and complexation constants and complex stoichiometry for Cr³⁺ and Fe³⁺ complex have been determined. The fluorescent properties of ligand 2 make this compound able to act as a sensor able to discriminate between Cr³⁺ and Fe³⁺. Detection limits for these two cations have been evaluated.     

Reversible Clustering of Gold Nanoparticles under Confinement

A limiting factor of solvent‐induced nanoparticle self‐assembly is the need for constant sample dilution in assembly/disassembly cycles. Changes in the nanoparticle concentration alter the kinetics of the subsequent assembly process, limiting optical signal recovery. Herein, we show that upon confining hydrophobic nanoparticles in permeable silica nanocapsules, the number of nanoparticles participating in cyclic aggregation remains constant despite bulk changes in solution, leading to highly reproducible plasmon band shifts at different solvent compositions.     

Determination of Phenolic Compounds and the Antioxidant Capacity of Ximenia parviflora Benth. var. parviflora (Olacaceae) Fruit by High-Performance Liquid Chromatography with Diode Array Detection

The total phenolic and flavonoid content, phenolic composition, and in vitro antioxidant capacity of ethanolic extracts of Ximenia parviflora Benth. var. parviflora fruits collected at Zinaparo, Michoacan (in central Mexico) were determined. Fruit extracts present a high scavenging activity of 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis[3-ethylbenzothiazoline-6-sulfonic acid] radicals (71.49?±?0.11% and 85.00?±?1.29% inhibition, respectively). The four phenolic compounds identified in fruit extracts by high-performance liquid chromatography with diode array detection were gallic acid, chlorogenic acid, caffeic acid, and quercetin. X. parviflora fruits may be used as a starting material for the extraction of high value antioxidant phenolic compounds with potential applications in the pharmaceutical and dietary supplement industries.     

Estimation and correction of matrix effects in gas chromatographic pesticide multiresidue analytical methods with a nitrogen-phosphorus detector

The assessment of matrix effects in the quantification of organophosphorus pesticides in fruit and vegetables by GC-NPD, were studied applying ANCOVA. Calibration curves prepared in solvent were compared with calibration curves prepared in a blank matrix extract for eight different commodities, establishing whether the matrix induces systematic or proportional errors in the quantification of the pesticides. In such cases correction functions were obtained and validated by quantifying spiked samples using solvent calibrations and applying the correction functions to the data obtained. The results were compared with those obtained by quantification using matrix-matching calibrations and with those from 100% recovery experiments. It was found that the matrix effects can be avoided using the correction functions. Finally the contribution of the correction functions to the uncertainty of the results was estimated as well as their stability during a four month period.