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Electron Capture (electron + capture)

Distribution by Scientific Domains
Chemistry100%

Terms modified by Electron Capture

  • electron capture detection
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  • electron capture dissociation
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    Selected Abstracts

    Determination of the pesticides considered as endocrine-disrupting compounds (EDCs) by solid-phase extraction followed by gas chromatography with electron capture and mass spectrometric detection

    JOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2007
    Vasiliki I. Valsamaki
    Abstract An SPE method followed by GC-electron capture detection (ECD) with confirmation by MS for the trace determination of four pesticides considered as endocrine-disrupting compounds (EDCs) in natural waters and sediments has been developed. Target analytes, fenarimol, fenvalerate, pendimethalin, and vinclozolin, belong to different chemical groups and are used mainly in agriculture. In the present study, analysis employs an offline SPE step for the extraction of the target analytes from natural waters. Sonication and subsequent SPE clean-up was used for extraction and purification of the sediment samples which were finally treated with activated copper powder. The type of SPE disk, eluents as well as solution parameters including pH value, and concentrations of salts and humic substances were examined for the efficiency of the method. The recoveries of all pesticides were in relatively high levels, ranging from 75 to 97% for waters and 71 to 84% for sediment samples. Both methods were applied to real water and sediment samples and the presence of the tested compounds was investigated. [source]

    Ultraviolet photofragmentation of biomolecular ions

    MASS SPECTROMETRY REVIEWS, Issue 3 2009
    James P. Reilly
    Abstract Mass spectrometric identification of all types of molecules relies on the observation and interpretation of ion fragmentation patterns. Peptides, proteins, carbohydrates, and nucleic acids that are often found as components of complex biological samples represent particularly important challenges. The most common strategies for fragmenting biomolecular ions include low- and high-energy collisional activation, post-source decay, and electron capture or transfer dissociation. Each of these methods has its own idiosyncrasies and advantages but encounters problems with some types of samples. Novel fragmentation methods that can offer improvements are always desirable. One approach that has been under study for years but is not yet incorporated into a commercial instrument is ultraviolet photofragmentation. This review discusses experimental results on various biological molecules that have been generated by several research groups using different light wavelengths and mass analyzers. Work involving short-wavelength vacuum ultraviolet light is particularly emphasized. The characteristics of photofragmentation are examined and its advantages summarized. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:425,447, 2009 [source]

    The role of electron capture dissociation in biomolecular analysis

    MASS SPECTROMETRY REVIEWS, Issue 2 2005
    Helen J. Cooper
    Abstract The introduction of electron capture dissociation (ECD) to electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) constitutes a significant advance in the structural analysis of biomolecules. The fundamental features and benefits of ECD are discussed in this review. ECD is currently unique to FT-ICR MS and the fundamentals of that technique are outlined. The advantages and complementarity of ECD in relation to other tandem mass spectrometry (MS/MS) techniques, such as infrared multiphoton dissociation (IRMPD) and sustained off-resonance collision-induced dissociation (SORI-CID), are discussed. The instrumental considerations associated with implementation of ECD, including activated ion techniques and coupling to on-line separation techniques, are covered, as are the allied processes electronic excitation dissociation (EED), electron detachment dissociation (EDD), and hot electron capture (HECD). A major theme of this review is the role of ECD in proteomics, particularly for characterization of post-translational modifications (phosphorylation, glycosylation, carboxyglutamic acid, sulfation, acylation, and methionine oxidation) and the top-down approach to protein identification. The application of ECD to the analysis of polymers, peptide nucleic acids, and oligonucleotides is also discussed. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:201,222, 2005 [source]

    Electron capture dissociation mass spectrometry of peptide cations containing a lysine homologue: a mobile proton model for explaining the observation of b-type product ions

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2006
    Sunyoung Lee
    Eleven doubly protonated peptides with a residue homologous to lysine were investigated by electron capture dissociation mass spectrometry (ECD-MS). Lysine homologues provide the unique opportunity to examine the ECD fragmentation behavior by allowing us to vary the length of the lysine side chain, with minimal structural change. The lysine homologue has a primary amine side chain with a length that successively decreases by one methylene (CH2) unit from the CH2CH2CH2CH2NH2 of lysine and the accompanying decrease of its proton affinities: lysine (K), 1006.5(±7.2) kJ/mol; ornithine (K*), 1001.1(±6.6) kJ/mol; 2,4-diaminobutanoic acid (K**), 975.8(±7.4) kJ/mol; 2,3-diaminopropanoic acid (K***), 950.2(±7.2) kJ/mol. In general, the lysine-homologous peptides exhibited overall ECD fragmentation patterns similar to that of the lysine-containing peptides in terms of the locations, abundances, and ion types of products, such as yielding c+ and z+. ions as the dominant product ions. However, a close inspection of product ion mass spectra showed that ECD-MS for the alanine-rich peptides with an ornithinyl or 2,4-diaminobutanoyl residue gave rise to b ions, while the lysinyl-residue-containing peptides did not, in most cases, produce any b ions. The peptide selectivity in the generation of b+ ions could be understood from within the framework of the mobile proton model in ECD-MS, previously proposed by Cooper (Ref. 29). The exact mass analysis of the resultant b ions reveals that these b ions are not radical species but rather the cationic species with R-CO+ structure (or protonated oxozalone ion), that is, b+ ions. The absence of [M+2H]+. species in the ECD mass spectra and the selective b+ -ion formation are evidence that the peptides underwent H-atom loss upon electron capture, and then the resulting reduced species dissociated following typical MS/MS fragmentation pathways. This explanation was further supported by extensive b+ ions generated in the ECD of alanine-based peptides with extended conformations. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Targeted lipidomics using electron capture atmospheric pressure chemical ionization mass spectrometry

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2003
    Seon Hwa Lee
    There is an increasing need to be able to conduct quantitative lipidomics analyses as a complement to proteomics studies. The highest specificity for proteomics analysis can be obtained using methodology based on electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) coupled with liquid chromatography/tandem mass spectrometry (LC/MS/MS). For lipidomics analysis it is often necessary to be able to separate enantiomers and regioisomers. This can be very challenging when using methodology based on conventional reversed-phase chromatography. Normal-phase chromatography using chiral columns can provide dramatic improvements in the resolution of enantiomers and regioisomers. However, conventional ESI- and APCI-MS/MS has limited sensitivity, which makes it difficult to conduct studies in cell culture systems where only trace amounts of non-esterified bioactive lipids are present. The use of electron capture APCI-MS/MS overcomes this problem. Enantiomers and regioisomers of diverse bioactive lipids can be quantified using stable isotope dilution methodology coupled with normal-phase chiral chromatography and electron capture APCI-MS/MS. This methodology has allowed a lipidomics profile from rat epithelial cells maintained in culture to be delineated and allowed the effect of a non-selective lipoxygenase inhibitor to be assessed. Copyright © 2003 John Wiley & Sons, Ltd. [source]