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941.
942.
Fourel F Martineau F Lécuyer C Kupka HJ Lange L Ojeimi C Seed M 《Rapid communications in mass spectrometry : RCM》2011,25(19):2691-2696
We have used a high‐precision, easy, low‐cost and rapid method of oxygen isotope analysis applied to various O‐bearing matrices, organic and inorganic (sulfates, nitrates and phosphates), whose 18O/16O ratios had already been measured. It was first successfully applied to 18O analyses of natural and synthetic phosphate samples. The technique uses high‐temperature elemental analysis–pyrolysis (EA‐pyrolysis) interfaced in continuous‐flow mode to an isotope ratio mass spectrometry (IRMS) system. Using the same pyrolysis method we have been able to generate a single calibration curve for all those samples showing pyrolysis efficiencies independent of the type of matrix pyrolysed. We have also investigated this matrix‐dependent pyrolysis issue using a newly developed pyrolysis technique involving 'purge‐and‐trap' chromatography. As previously stated, silver phosphate being a very stable material, weakly hygroscopic and easily synthesized with predictable 18O/16O values, could be considered as a good candidate to become a reference material for the determination of 18O/16O ratios by EA‐pyrolysis‐IRMS. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
943.
Fletcher JS Rabbani S Henderson A Lockyer NP Vickerman JC 《Rapid communications in mass spectrometry : RCM》2011,25(7):925-932
Time-of-flight secondary ion mass spectrometry (ToFSIMS) is being applied increasingly to the study of biological systems where the chemical specificity of mass spectrometry and the high lateral resolution imaging capabilities can be exploited. Here we report a comparison of two cell sample preparation methods and demonstrate how they influence the outcome of the ToFSIMS analysis for three-dimensional (3D) imaging of biological cells using our novel buncher-ToF instrument (J105 3D Chemical Imager) equipped with a C(60) primary ion beam. Cells were analysed fixed and freeze-dried and non-fixed, frozen-hydrated. It is concluded that maintaining the cells in a non-fixed frozen-hydrated state during the analysis helps reduce chemical redistribution, producing cleaner spectra and improved chemical contrast in both 2D and 3D imaging. Insights into data interpretation are included and we present methods for 3D reconstruction of the data using multivariate analysis techniques. 相似文献
944.
Michael J. Silva Alex O. Sanches Luiz F. Malmonge Eliton S. Medeiros Morsyleide F. Rosa Colleen M. McMahan José A. Malmonge 《Macromolecular Symposia》2012,319(1):196-202
Summary: Cellulose nanofibrils (CNF) were extracted by acid hydrolysis from cotton microfibrils and nanocomposites with polyaniline doped with dodecyl benzenesulphonic acid (PANI-DBSA) were obtained by in situ polymerization of aniline onto CNF. The ratios between DBSA to aniline and aniline to oxidant were varied in situ and the nanocomposites characterized by four probe DC electrical conductivity, ultraviolet-visible-near infrared (UV-Vis - NIR) and Fourier-transform infrared (FTIR) spectroscopies and X-ray diffraction (XRD). FTIR and UV-Vis/NIR characterization confirmed the polymerization of PANI onto CNF surfaces. Electrical conductivity of about 10−1 S/cm was achieved for the composites; conductivity was mostly independent of DBSA/aniline (between 2 and 4) and aniline/oxidant (between 1 and 5) molar ratios. X-ray patterns of the samples showed crystalline peaks characteristic of cellulose I for CNF samples, and a mixture of both characteristic peaks of PANI and CNF for the nanocomposites. Field emission scanning electron microscopy (FESEM) characterization corroborated the abovementioned results showing that PANI coated the surface of the nanofibrils. 相似文献
945.
Murphy LJ McPherson AM Robertson KN Clyburne JA 《Chemical communications (Cambridge, England)》2012,48(9):1227-1229
Amines dissolved in ionic liquids react rapidly with SO(2) to produce new materials. Compounds related to the stepwise conversion of SO(2) to sulfite and sulfate salts have been isolated. Trapping SO(2) in the form of the sulfite anion does not change the oxidation state of sulfur and should maintain the reversibility of the capture system. 相似文献
946.
Shi Z Davies J Jang SH Kaminsky W Jen AK 《Chemical communications (Cambridge, England)》2012,48(63):7880-7882
The AIE properties of two trifluoromethyl substituted distyrylbenzene model compounds were compared. The fluorescence quantum efficiency of these molecules can be modulated by tuning their subtle solid-state intermolecular interactions. 相似文献
947.
Ortiz M Wajs EM Fragoso A O'Sullivan CK 《Chemical communications (Cambridge, England)》2012,48(7):1045-1047
Self-assembly of a ferrocene-appended polymer bearing an antigen fragment and lactate oxidase on a cyclodextrin-modified surface provides a highly sensitive, easy-to-operate and self-sufficient immunosensor. 相似文献
948.
949.
950.
HJ Russell AR Jones S Hay GM Greetham M Towrie NS Scrutton 《Angewandte Chemie (International ed. in English)》2012,51(37):9306-9310
The role of protein dynamics in promoting catalysis is hotly debated. Infrared data from both ultrafast flash photolysis and stopped-flow studies show that not only does there appear to be vibrational coupling between the cofactor and protein in B(12) -dependent ethanolamine ammonia lyase, but also that there are significant protein motions coupled to the reaction that follows substrate binding. 相似文献