Some aspects of the analysis of environmental pollutants in sediments using pressurized liquid extraction and gas chromatography-mass spectrometry

Pressurized liquid extraction (PLE) is a fully automated extraction technique for isolation of analytes from solid samples. This technique combines elevated temperature and pressure of liquid solvents during the extraction process. In this study the efficiency of a PLE system for the isolation of wide range of analytes (polychlorinated biphenyls and organic pesticides from sediments under different pressure and temperature conditions) was investigated. The temperature 100 degrees C and pressure 6.9 MPa (1000 p.s.i.; 1 p.s.i.=6894.76 Pa) were found to be the most efficient from all investigated conditions. Using these PLE parameters, the average recoveries for most of the analytes were in the range 80-105% and relative standard deviation was usually under 15%. The conditions of determination of analytes in the extracts using GC-MS were established. Some problems occurring during the analysis of real samples, such as coelution of analytes, were established. The influence of internal standard addition on the final analysis results was determined.     

Interactions in open-shell clusters: ab initio study of pre-reactive complex O(3P) + HCl

Van der Waals interactions between the ground-state triplet O(3P) atom and the closed-shell HCl molecule are investigated in the pre-reactive region. Three adiabatic (two of A' symmetry and one of A' symmetry) and four non-relativistic diabatic potential energy surfaces are obtained by combining a restricted open-shell coupled cluster approach with the multireference configuration interaction method. The lower A' adiabatic potential surface has a single minimum (D(e) = 589 cm(-1)) for a linear O...HCl configuration. The upper A' potential has a weak (D(e) = 65 cm(-1)) minimum for a linear HCl...O configuration. The A' adiabatic potential has a weak (124 cm(-1)) T-shaped minimum. Adiabatic potentials intersect once in the O...HCl linear configuration and twice in the linear HCl...O geometry. The role of electrostatic interactions in shaping these potentials is discussed. The effects of spin-orbit coupling on this interaction are also investigated assuming a constant value of the SO parameter.     

Intramolecular Radical Aziridination of Allylic Sulfamoyl Azides by Cobalt(II)‐Based Metalloradical Catalysis: Effective Construction of Strained Heterobicyclic Structures

Cobalt(II)‐based metalloradical catalysis (MRC) has been successfully applied for effective construction of the highly strained 2‐sulfonyl‐1,3‐diazabicyclo[3.1.0]hexane structures in high yields through intramolecular radical aziridination of allylic sulfamoyl azides. The resulting [3.1.0] bicyclic aziridines prove to be versatile synthons for the preparation of a diverse range of 1,2‐ and 1,3‐diamine derivatives by selective ring‐opening reactions. As a demonstration of its application for target synthesis, the metalloradical intramolecular aziridination reaction has been incorporated as a key step for efficient synthesis of a potent neurokinin 1 (NK₁) antagonist in 60 % overall yield.     

Palladacyclic and platinacyclic catalysts for the allylation of aldehydes

A range of palladacyclic and platinacyclic catalysts have been tested for activity in the allylation of aldehydes with allyl tributyltin. The bulky, π-acidic palladacycle [{Pd(μ-Cl){κ²-P,C-P(OC₆H₂-2,4-^tBu₂)(OC₆H₃-2,4-^tBu₂)₂}}₂] shows particularly good activity at room temperature with a variety of unsaturated substrates.     

A practical demonstration of electronic promotion in the reduction of ceria coated PGM catalysts

When ceria is deposited over supported PGM catalysts its reducibility is dependent on the work function of the underlying metal.     

Profiling isoflavone conjugates in root extracts of lupine species with LC/ESI/MSn systems

Extracts obtained from roots of three lupine species (Lupinus albus, L. angustifolius, L. luteus) were analysed using LC/UV and LC/ESI/MS(n). The experiments were performed using two mass spectrometric systems, equipped with the triple quadrupole or ion trap analysers. Thirteen to twenty isomeric isoflavone conjugates were identified in roots of the investigated lupine species. These were di- and monoglycosides of genistein and 2'-hydroxygenistein with different patterns of glycosylation, both at oxygen and carbon atoms; some glycosides were acylated with malonic acid. It was not possible to establish the glycosylation sites of the aglycone only on the basis of the registered mass spectra; however, it was possible to differentiate C- and O-glucosides of isoflavones. Only comparison of retention times with those of standard compounds permitted to indicate the correct glycosylation pattern. In the case of diglycosides, the glycosylation pattern (O-diglucoside or O-glucosylglucoside) was distinguishable on the basis of the relative intensities of daughter ions in the mass spectra of protonated molecular ions. It was not possible to elucidate the site of malonylation on the sugar moiety from mass spectra, however, protonated molecules [M + H](+) of isoflavone glucosides with different placement of the malonyl group on the sugar ring were recognized in the extracts. In addition to the isoflavone glycosides, some flavone or flavonol glycosides were identified in the samples on the basis of collision-induced daughter ion spectra of the aglycone ions. A comparison of results obtained with the triple quadrupole and ion trap analysers was done in the course of the investigations.     

Ferrocene as a Reference Redox Couple for Aprotic Ionic Liquids

The electrochemical behavior of ferrocene has been studied in a number of room temperature ionic liquids. Diffusion‐controlled, well‐defined anodic and cathodic peaks were found for the Fc/Fc⁺ (ferrocene/ferrocenium) oxidation/reduction on the gold electrode. Ohmic resistance R between working and auxiliary electrodes was deduced from impedance measurements. Cyclic voltammograms were corrected for the base line current as well as for the ohmic drop (IR). The formal potential 1/2(E_pa+E_pc) for ferrocene reduction/oxidation in aprotic ionic liquids tested is within a relatively narrow range and may be approximated by the value of 0.527±0.018 V (against the cryptate Ag/Ag⁺222 in acetonitrile reference). Ferrocene diffusion coefficients, calculated from the peak current dependence on the sweep rate, were of the order of 10^?7 cm² s^?1.     

On the modelling of highly elastic flows of amorphous thermoplastics

Two approaches to the kinematic structuring of constitutive models for highly elastic flows of polymer melts have been examined systematically, assuming either: (1) additivity of elastic and viscous velocity gradients or (2) multiplicability of elastic and viscous deformation gradients. A series of constitutive models were compared, with differing kinematic structure but the same linear responses in elastic and viscous limits. They were solved numerically and their predictions compared, and they were also compared to those of the Giesekus model. Several variants, previously proposed as separate models, are shown to be equivalent and qualitatively in agreement with experiment, and therefore a sound basis for construction of models. But the assignment of viscous spin is critical: if it is assumed equal to the total spin with approach (1), or equal to zero with approach (2), then unphysical viscoelastic behaviour is predicted.