Determination of phthalates in water using fiber introduction mass spectrometry

Fiber introduction mass spectrometry (FIMS) - a direct coupling of SPME and MS - using selective ion monitoring (SIM) was used to detect and quantify dimethylphthalate (DMP), diethylphthalate (DEP) and dipropylphthalate (DPP) in mineral water. In FIMS, a chromatographic silicone septum is the only barrier between ambient and the high-vacuum mass spectrometer, permitting direct introduction of the SPME fiber into the ionization region of the equipment. After their thermal desorption and ionization and dissociation, the extracted phthalates are detected and quantitated by MS. Three types of SPME fibers were screened for best analyte sorption/desorption behaviors: 100 mum polydimethylsiloxane ( PDMS), 65 mum polydimethylsiloxane/divinylbenzene (PDMS/DVB) and 65 mum Carbowax/divinylbenzene (CW/DVB). The PDMS/DVB and CW/DVB fibers were then evaluated for precision, and quantitative figures of merit were assessed for extractions using the PDMS/DVB fiber, which displayed the best overall performance. FIMS with the PDMS/DVB fiber allows simple extraction and MS detection and quantitation of DMP in water with good linearity and precision, and at concentrations as low as 3.6 mug L-1. The LD and LQ of FIMS are below the maximum phthalate concentration allowed by the USEPA for drinking water ( 6 mug L-1).130218819

Solid phase micro-extraction in a miniature ion trap mass spectrometer

Fiber introduction mass spectrometry (FIMS), a variation of solid-phase microextraction (SPME) and membrane introduction mass spectrometry (MIMS), is employed with a miniature mass spectrometer. The inlet system, constructed of commercially available vacuum parts, allows the direct introduction of the SPME needle vacuum chamber into the mass spectrometer. Thermal desorption of the analyte from the poly(dimethylsiloxane) (PDMS) coated fiber was achieved with a built in nichrome heater, followed by electron ionization of the analytes internal to the cylindrical ion trap (CIT). The system has been tested with several volatile organic compounds (VOC) in air and to analyze the headspace over aqueous solutions, with limits of detection in the low ppb range. The signal rise (10-90%) and fall (90-10%) times for the system ranged from 0.1 to 1 s (rise) and 1.2 to 6 s (fall) using heated desorption. In addition, this method has been applied to quantitation of toluene in benzene, toluene, xylene (BTX) mixtures in water and gasoline. This simple and rapid analysis method, coupled to a portable mass spectrometer, has been shown to provide a robust, simple, rapid, reproducible, accurate and sensitive (low ppb range) fieldable approach to the effective in situ analysis of VOC in various matrices.12891119112

Cold gas accretion in galaxies

Evidence for the accretion of cold gas in galaxies has been rapidly accumulating in the past years. HI observations of galaxies and their environment have brought to light new facts and phenomena which are evidence of ongoing or recent accretion: 1) A large number of galaxies are accompanied by gas-rich dwarfs or are surrounded by HI cloud complexes, tails and filaments. It may be regarded as direct evidence of cold gas accretion in the local universe. It is probably the same kind of phenomenon of material infall as the stellar streams observed in the halos of our galaxy and M31. 2) Considerable amounts of extra-planar HI have been found in nearby spiral galaxies. While a large fraction of this gas is produced by galactic fountains, it is likely that a part of it is of extragalactic origin. 3) Spirals are known to have extended and warped outer layers of HI. It is not clear how these have formed, and how and for how long the warps can be sustained. Gas infall has been proposed as the origin. 4) The majority of galactic disks are lopsided in their morphology as well as in their kinematics. Also here recent accretion has been advocated as a possible cause. In our view, accretion takes place both through the arrival and merging of gas-rich satellites and through gas infall from the intergalactic medium (IGM). The infall may have observable effects on the disk such as bursts of star formation and lopsidedness. We infer a mean ``visible'' accretion rate of cold gas in galaxies of at least 0.2 Msol/yr. In order to reach the accretion rates needed to sustain the observed star formation (~1 Msol/yr), additional infall of large amounts of gas from the IGM seems to be required.Comment: To appear in Astronomy & Astrophysics Reviews. 34 pages. Full-resolution version available at http://www.astron.nl/~oosterlo/accretionRevie

A change in the optical polarization associated with a gamma-ray flare in the blazar 3C 279

It is widely accepted that strong and variable radiation detected over all accessible energy bands in a number of active galaxies arises from a relativistic, Doppler-boosted jet pointing close to our line of sight. The size of the emitting zone and the location of this region relative to the central supermassive black hole are, however, poorly known, with estimates ranging from light-hours to a light-year or more. Here we report the coincidence of a gamma-ray flare with a dramatic change of optical polarization angle. This provides evidence for co-spatiality of optical and gamma-ray emission regions and indicates a highly ordered jet magnetic field. The results also require a non-axisymmetric structure of the emission zone, implying a curved trajectory for the emitting material within the jet, with the dissipation region located at a considerable distance from the black hole, at about 10^5 gravitational radii.Comment: Published in Nature issued on 18 February 2010. Corresponding authors: Masaaki Hayashida and Greg Madejsk

A novel design process for selection of attributes for inclusion in discrete choice experiments:Case study exploring variation in clinical decision-making about thrombolysis in the treatment of acute ischaemic stroke

On-line structured prioritisation exercise (SPE). Full survey used to collect data. (DOCX 42 kb

In vivo glioblastoma growth is reduced by apyrase activity in a rat glioma model

BACKGROUND: ATP is an important signalling molecule in the peripheral and central nervous system. Both glioma growth and tumor resection induces cell death, thus liberating nucleotides to the extracellular medium. Nucleotides are hydrolyzed very slowly by gliomas when compared with astrocytes and induce neuronal cell death and glioma proliferation. The objective of the present study was to test the involvement of extracellular ATP in glioblastoma growth in a rat glioma model. METHODS: To deplete the extracellular ATP, the enzyme apyrase was tested on the treatment of gliomas implanted in the rats CNS. One million glioma C6 cells in 3 microliters of DMEM/FCS were injected in the right striata of male Wistar rats, 250–270 g. After 20 days, the rats were decapitated and the brain sectioning and stained with hematoxylin and eosine. We performed immunohistochemical experiments with Ki67, CD31 and VEGF. Total RNA was isolated from cultured glioma C6 cells and the cDNA was analyzed by Real Time-PCR with primers for the NTPDase family. RESULTS: C6 glioma cells effectively have a low expression of all NTPDases investigated, in comparison with normal astrocytes. The implanted glioma co-injected with apyrase had a significant reduction in the tumor size (p < 0.05) when compared with the rats injected only with gliomas or with gliomas plus inactivated apyrase. According to the pathological analysis, the malignant gliomas induced by C6 injection and co-injected with apyrase presented a significant reduction in the mitotic index and other histological characteristics that indicate a less invasive/proliferative tumor. Reduction of proliferation induced by apyrase co-injection was confirmed by counting the percentage of Ki67 positive glioma cell nuclei. According to counts with CD31, vessel density and neoformation was higher in the C6 group 20 days after implantation. Confirming this observation, rats treated with apyrase presented less VEGF staining in comparison to the control group. CONCLUSION: These results indicate that the participation of extracellular ATP and the ecto-nucleotidases may be associated with the development of this type of brain tumor in an in vivo glioma model

Cyclization of acylium ions with nitriles: gas-phase synthesis and characterization of 1,3,5-oxadiazinium ions

Gas phase reactions of mass-selected acylium ions [CH3-C+=O (1), CH2=CH-C+=O (2), C6H5-C+=O (3), and (CH3)(2)N-C+=O (4)] with nitriles (CH3CN, C2H5CN, CH2=CHCN, and C6H5CN) were investigated using pentaquadrupole multiple-stage mass spectrometry. In analogy with the solution behavior, the ions were found to react readily with benzonitrile by cyclization via double nitrile addition to form aromatic 1,3,5-oxadiazinium ions. Cyclization with acetonitrile, propionitrile, and acrylonitrile is less general and occurs readily only for 4, by far the most reactive acylium ion tested. In "one-pot" reactions of 4 with two-component nitrile mixtures, cyclization via double nitrile addition occurs readily and forms both equally and differently 4,6-disubstituted isomeric 1,3,5-oxadiazinium ions. Using MS' experiments, the 1,3,5-oxadiazinium ions were mass-selected and then either reacted with nitrogen nucleophiles or dissociated by low-energy collisions with argon. The nucleophiles add readily to the ions, whereas the symmetry of the 1,3,5-oxadiazinium ring allows two competitive dissociation pathways: double retro-addition that re-forms the reactant acylium ion, or an analogous dissociation that, formally and combined with cyclization, promotes group exchange between one nitrile and the acylium ion: RCO+ + 2 (RCN)-C-1 --> cyclic 1,3,5-oxadiazinium ion --> (RCO+)-C-1 (RCN)-C-1 + RCN. Isomeric 4,6-disubstituted 1,3,5-oxadiazinium ions are easily distinguished because the nitrile added second is lost first via the double retro-addition dissociation. (C) 2001 Elsevier Science B.V.2124169944545

Formal gas-phase polar [4+1(+)] cycloaddition of ionized methylene to alpha-dicarbonyl compounds: synthesis of 2-unsubstituted 1,3-dioxoles

Ion/molecule reactions of +CH2OCH2 with alpha-dicarbonyl compounds were performed via pentaquadrupole mass spectrometry. Besides the previously known [3(+) + 2] 1,3-cycloaddition reaction that forms cyclic 1,3-dioxonium ions, an unprecedented reaction proceeding formally by [4 + 1(+)] cycloaddition of ionized methylene (CH2+) to the alpha-dicarbonyl compounds occurs competitively, leading to the gas-phase synthesis of several ionized 2-unsubstituted 1,3-dioxoles. This novel cycloaddition reaction may therefore be added to the set of methods available for the synthesis of 1,3-dioxoles. Copyright (c) 2006 John Wiley & Sons, Ltd.41673574