Interferences in ultratrace speciation of organolead and organotin by gas chromatography with atomic spectrometric detection

Interferences in trace and ultratrace speciation analysis of organotin and organolead compounds in various samples by gas chromatography coupled with atomic absorption spectrometry (AAS) and/or microwave induced plasma atomic emission spectrometry (MIP AES) are investigated. Particular attention is given to the effects of matrix co-extractives and reagents impurities introduced during sample preparation. Their influence on the detection limits is discussed in terms of baseline noise level, blank value, formation of artefacts and signal suppression. Loss of column resolution during the analysis of some matrices is observed.     

Multitechnique mass-spectrometric approach for the detection of bovine glutathione peroxidase selenoprotein: focus on the selenopeptide

Glutathione peroxidase (isolated from bovine erythrocytes) and its behaviour during alkylation and enzymatic digestion were studied by various hyphenated techniques: gel electrophoresis–laser ablation (LA) inductively coupled plasma (ICP) mass spectrometry (MS), size-exclusion liquid chromatography–ICP MS, capillary high-performance liquid chromatography (capHPLC)–ICP MS, matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) MS, electrospray MS, and nanoHPLC–electrospray ionization (ESI) MS/MS. ESI TOF MS and MALDI TOF MS allowed the determination of the molecular mass but could not confirm the presence of selenium in the protein. The purity of the protein with respect to selenium species could be evaluated by LA ICP MS and size-exclusion chromatography (SEC)–ICP MS under denaturating and nondenaturating conditions, respectively. SEC–ICP MS and capHPLC–ICP MS turned out to be valuable techniques to study the enzymolysis efficiency, miscleavage and artefact formation during derivatization and tryptic digestion. For the first time the parallel ICP MS and ESI MS/MS data are reported for the selenocysteine-containing peptide extracted from the gel; capHPLC–ICP MS allowed the sensitive detection of the selenopeptide regardless of the matrix and nanoHPLC–electrospray made possible its identification. Figure Eye catching image Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The Baum-Connes Conjecture via Localization of Categories

We redefine the Baum-Connes assembly map using simplicial approximation in the equivariant Kasparov category. This interpretation is ideal for studying functorial properties and gives analogues of the Baum-Connes assembly map for all equivariant homology theories.     

Diffusion of nickel on the (110) region of a tungsten field emitter

The diffusion of nickel atoms on the (110) plane of a thermally cleaned tungsten crystal has been investigated by a field emission technique. The measurements were carried out for low nickel coverage and substrate temperatures T390 K when the nickel atoms escape from the (110) plane to its surroundings. the value of the activation energy obtained, Q=0.96 eV, is discussed taking into account the conditions under which diffusion occurs.     

An ion-imprinted thiocyanato-functionalized mesoporous silica for preconcentration of gold(III) prior to its quantitation by slurry sampling graphite furnace AAS

A gold(III)-imprinted thiocyanato-functionalized silica network of type SBA-15 was prepared by co-condensation of tetraethoxysilane (TEOS) with thiocyanatopropyltriethoxysilane (TCTES) in the presence of Pluronic123 and Au(III) ions. Compared to the non-imprinted material, the imprint has a higher selectivity and adsorption capacity for Au(III). The maximum static adsorption capacity for Au(III) is 475 mg·g^?1 for the ion-imprinted, and 62 mg·g^?1 for the non-imprinted sorbent. The imprint was applied to the sorption of Au(III) from digested geological samples prior to its determination by graphite furnace atomic absorption spectrometry. Adsorption is fast and does not substantially prolong the analytical procedure. Under optimum conditions, the detection limit for Au(III) is 2 ng·g^?1. The method was validated by analyzing certified reference materials, and results were in good agreement with certified values. The procedure was successfully applied to the separation and determination of gold in complex geological samples.

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Graphical abstract Schematic presentation of the preparation of ion-imprinted thiocyanato-functionalized mesoporous silica and its application for the preconcentration of gold from digested soils before its determination by slurry sampling graphite furnace atomic absorption spectrometry (GF AAS).

     

Conformational mobility in chemically-modified cyclodextrins

The observation that per-2,6-O-methyl-3-O-benzoyl--cyclodextrin (1) displays some unusual conformational behaviour in solution has led to a detailed investigation by (dynamic) NMR spectroscopy of the equilibration process that occurs in solutions of per-2,3-O-benzoyl--cyclodextrin (3) and some related compounds (7–9) between conformational isomers with averagedC ₆ andC ₃ molecular symmetries in certain organic solvents such as benzene, dichloromethane, and chloroform. The solvent dependence of the conformational equilibrium is also reflected in a spread of values for the specific optical rotations for 3 from +9° in 1,1,2,2-tetrachloroethane, where there is a degenerate equilibrium between species withC ₃ molecular symmetry, to +92° in acetone where a species with averagedC ₆ symmetry is present.This paper is dedicated to the memory of the late Dr C. J. Pedersen.