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81.
C. J. Proctor B. Kralj A. G. Brenton J. H. Beynon 《Journal of mass spectrometry : JMS》1980,15(12):619-631
Over thirty consecutive reactions of a type m1+ → m2+ → m3+ have been studied in a variety of organic compounds using a reversed geometry mass spectrometer. Two field free regions allow the separation of the two steps that make up the consecutive reaction sequence. Translational energy release measurements are used in the comparison of m2+ ions formed as a result of a high energy process in the ion source with m2+ ions formed as a product of a metastable decomposition. In some cases the structures of such ions have been found to be different. Examples have also been found where consecutive fragmentations of metastable ions do not occur although, when higher energy ions within the source are studied, the two-step reaction does take place. Furthermore, it has been found that a control over ion internal energy may be achieved by selecting portions of a peak due to the fragmentation of a metastable ion. Unimolecular reactions may then be used to study the reactivity of such ‘energy-selected’ ions; collision induced reactions can be used to study the structure of both the reactive and unreactive energy selected ions. 相似文献
82.
Electron impact (EI), fast atom bombardment (FAB) and ammonia chemical ionization [CI(NH3)] mass spectrometry were applied with the aim of differentiating between the anomeric 1alpha- and 1beta-azidopentofuranosyl derivatives. Calculated ammonium affinities [AA(M)] and proton affinities [PA(M)] show that beta-anomers have higher affinities for H+ and NH4+ ions than alpha-azides. Protonated molecules, obtained by CI(NH3) of azidofuranosyl derivatives, lose HN3 giving abundant furanosyl (S+) ions. Ammonia solvation of MH+ ions competes with the previous reaction producing the [SNHN2NH3]+ ion, a competitive product to the ammonium-attached [SN3NH4]+ ion. The fragmentation pathways of the stable and metastable [MNH4]+, MH+ ions, and several other important fragment ions, were determined using mass analyzed ion kinetic energy spectrometry (MIKES). The abundance of the [SN3NH4]+ and/or [SNHN2NH3]+ ions was found to correlate inversely with the exothermicity of ammonia solvation of the MH+ ion. The abundance of the fragment ions [SNHNH3]+, [SNH3]+ and SNH+ in some examples correlates with the exothermicity of the corresponding [MNH4]+ and MH+ parent ion formation. The fragment ions SNH3+ and SNHNH3+ can be formed, at least in part, in the ammonia solvation reaction of the S+ and SNH+ ions taking place within the high-pressure region of the CI ion source. 相似文献
83.
Kralj D Kontrec J Brecević L Falini G Nöthig-Laslo V 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(7):1647-1656
Calcium carbonate was precipitated from calcium hydroxide and carbonic acid solutions at 25 degrees C, with and without addition of different magnesium (MgSO(4), Mg(NO(3))(2) and MgCl(2)) and sodium salts (Na(2)SO(4), NaNO(3) and NaCl) of identical anions, in order to study the mode of incorporation of magnesium and inorganic anions and their effect on the morphology of calcite crystals over a range of initial reactant concentrations and limited c(i)(Mg(2+))/c(i)(Ca(2+)) molar ratios. The morphology, crystal size distribution, composition, structure, and specific surface area of the precipitated crystals, as well as the mode of cation and anion incorporation into the calcite crystal lattice, were studied by a combination of optical and scanning electron microscopy (SEM), electronic counting, a multiple BET method, thermogravimetry, FT-IR spectroscopy, X-ray diffraction (XRD), and electron paramagnetic resonance (EPR) spectroscopy. In the systems of high initial relative supersaturation, precipitation of an amorphous precursor phase preceded the formation of calcite, whereas in those of lower supersaturation calcite was the first and only polymorphic modification of calcium carbonate that appeared in the system. The magnesium content in calcite increased with the magnesium concentration in solution and was correlated with the type of magnesium salt used. Mg incorporation caused the formation of crystals elongated along the calcite c axis and, in some cases, the appearance of new [011] faces. Polycrystalline aggregates were formed when the c(i)(Mg(2+))/c(i)(Ca(2+)) molar ratios in solution were increased. Addition of sulfate ions, alone, caused formation of spherical calcite polycrystalline aggregates. 相似文献
84.
N. Filipović-Marinić V. Rapić V. Kramer B. Kralj 《Journal of organometallic chemistry》1985,296(3):405-409
The mass-analyzed ion kinetic energy (MIKE) spectra of some monosubstituted ferrocenes having an unsaturated moiety in the α- or β-position to the cyclopentadienyl ring and β-phenyl-γ-ferrocenoylbutyric acid are presented and discussed. 相似文献
85.
Spectra of a series of solutions containing different concentrations of four solutes were simulated, assuming either normal or non-normal distribution of experimental errors. These synthetic data were then analyzed by linear least-squares procedures in order to estimate the spectra of individual solutes. Analysis of regression residuals and the estimated spectra showed that a correct set of statistical weights can be found by an iterative procedure, if the qualitative form of the weighting function is known in advance. When ever a least-squares estimation was successful, the estimates were practically unbiased and the moments of the distribution of regression residuals were close to their expectances. However, the distribution moments of the regression estimates were found to be far from normal in all cases, although the estimates were not necessarily biased. 相似文献
86.
87.
Integrated continuous microfluidic liquid-liquid extraction 总被引:1,自引:0,他引:1
We describe continuous flow liquid-liquid phase separation in microfluidic devices based on capillary forces and selective wetting surfaces. Effective liquid-liquid phase separation is achieved by using a thin porous fluoropolymer membrane that selectively wets non-aqueous solvents, has average pore sizes in the 0.1-1 microm range, and has a high pore density for high separation throughput. Pressure drops throughout the microfluidic network are modelled and operating regimes for the membrane phase separator are determined based on hydrodynamic pressure drops and capillary forces. A microfluidic extraction device integrating mixing and phase separation is realized by using silicon micromachining. Modeling of the phase separator establishes the operating limits. The device is capable of completely separating several organic-aqueous and fluorous-aqueous liquid-liquid systems, even with high fractions of partially miscible compounds. In each case, extraction is equivalent to one equilibrium extraction stage. 相似文献
88.
89.
Zidanšek Aleksander Hölbl Arbresha Ranjkesh Amid Cordoyiannis George Kutnjak Zdravko Kralj Samo 《The European physical journal. E, Soft matter》2022,45(7):1-8
The European Physical Journal E - In the nanoscale regime, flow behaviors for liquids show qualitative deviations from bulk expectations. In this work, we reveal by molecular dynamics simulations... 相似文献