High-throughput mass spectrometer using atmospheric pressure ionization and a cylindrical ion trap array

The analytical performance of an atmospheric pressure sampling, multiple-channel, high-throughput mass spectrometer was investigated using samples of a variety of types. The instrument, based on an array of cylindrical ion traps, was built with four independent channels and here is operated using two fully multiplexed channels (sources, ion optics, ion traps, detectors) capable of analyzing different samples simultaneously. Both channels of the instrument were incorporated within the same vacuum system and operated using a common set of control electronics. A multichannel electrospray ionization source was assembled and used to introduce samples including solutions of organic compounds, peptides, and proteins simultaneously into the instrument in a high-throughput fashion. Cross-talk between the channels of the instrument occurred in the detection system and could be minimized to 1-2% using shielding between detector channels. In this initial implementation of the instrumentation, an upper mass/charge limit of approximately 1300 Th was observed (+13 charge state of myoglobin) and unit mass/charge resolution was achieved to approximately 800 Th. The rather limited dynamic range (2-3 orders of magnitude for low-concentration analytes) is due to cross-talk contributions from more concentrated species introduced into a different channel. Analysis of mixtures of alkylamines and peptides is demonstrated, but analysis of mixtures with a wide spread in mass/charge ratios was not possible due to mass discrimination in the ion optics. Further refinement of the vacuum system and ion optics will allow the addition of more channels of parallel mass analysis and facilitate applications in fields such as proteomics and metabolomics.     

Multilayer silicon cavity mirrors for the far-infrared p-Ge laser

Multilayer mirrors capable of > 99.9% reflectivity in the far infrared (70-200 microm wavelengths) were constructed using thin silicon etalons separated by empty gaps. Calculations indicate that only three periods are required to produce 99.9% reflectivity because of the large difference between the index of refraction of silicon (3.384) and the vacuum (1). The mirror was assembled from high-purity silicon wafers, with resistivity over 4000 omega cm to reduce free-carrier absorption. Wafers were double-side polished with faces parallel within 10 arc sec. The multilayer mirror was demonstrated as a cavity mirror for the far-infrared p-Ge laser. Dependence of reflectivity on design accuracy was considered.     

Fatty Acid Biomarkers of Symbionts and Unusual Inhibition of Tetracosapolyenoic Acid Biosynthesis in Corals (Octocorallia)

Seven zooxanthellae-free species of octocorals (the genera Acanthogorgia, Acabaria, Chironephthya, Echinogorgia, Menella, Ellisella, and Bebryce) and two zooxanthellate octocorals (the genera Paralemnalia and Rumphella) were examined to elucidate their fatty acid (FA) composition. Arachidonic (about 40% of the total FA) and palmitic acids were predominant in all the species studied. Seven furan FA (F-acids) (up to 9.7%) were identified in the azooxanthellate octocorals. The main F-acids were 14,17-epoxy-15-methyldocosa-14,16-dienoic and 14,17-epoxy-15,16-dimethyldocosa-14,16-dienoic acids. In all specimens of Bebryce studeri, C_25–28 demospongic FA (about 20%) were identified. These FA reflect the presence of a symbiotic sponge in B. studeri and can be used as the specific markers for other corals. A significant difference (P < 0.01) between azooxanthellate and zooxanthellate corals was found for odd-chain and methyl-branched saturated FA, 18:1n-7, and 7-Me-16:1n-10; that indicated the presence of an advanced bacterial community in azooxanthellate corals. The zooxanthellate species were distinguished by significant amounts of 18:3n-6, 18:4n-3, and 16:2n-7 acids, which are proposed as the markers of zooxanthellae in soft corals. Contrary to the normal level of 24:5n-6 (9.4%) and 22:4n-6 (0.6%), unexpected low concentrations of 24:5n-6 (0.4%) accompanied by a high content of 22:4n-6 (up to 11.9%) were detected in some specimens. The presence of an unknown factor in octocorals, specific for n-6 PUFA, which inhibited elongation of 22:4n-6 to 24:4n-6, is conjectured.     

Dispersion of silver particles in aqueous solutions visualized by polarography/voltammetry

The State of silver particles in aqueous dispersions and the course of their coagulation can be followed on voltammetric curves recorded with hanging mercury drop electrode. Sharp irregular cathodic current peaks produced by partial electroreduction of the species adsorbed on the surface of silver particles during their fortuitous impingements upon the electrode surface appear in time sequence on the curves. A change in the electrochemical behavior of silver sols in the time course of particles aggregation and growth was interpreted in agreement with the data of UV–vis spectroscopy and electron microscopy observations.     

CFD predictions for hazardous area classification

This study aimed to describe a Computational Fluid Dynamics(CFD) procedure using the ANSYS CFX software 16.1 and Design of Experiments for the determination of volume and extension of explosive atmospheres due to fugitive emissions of flammable gases.The multidimensional statistical sampling technique Latin Hypercube was used, which defined 100 simulations of random methane gas leak conditions.The CFD model proved to be robust in predicting the extension and volume of the explosive atmosphere for orifice diameters from 0.1 to2.5 mm, pressure from 0.1 MPa to 12 MPa and temperatures from 0 ℃ to 400 ℃.It was found that the calculation domain must be parameterized 8 m in length for each millimeter of the diameter of the source of release to ensure the predictions.In order not to lose precision for very small diameters, the mesh was parameterized with 50 elements along the orifice diameter.It was proved that gravity does not influence the extension and volume of the explosive atmosphere at sonic emissions.The deviation from the ideal gas behavior in the reservoir,achieved by applying the Soave–Redlich–Kwong equation of state, also has not significantly influenced the extension and volume of the explosive atmosphere.The results showed that the size of the explosive atmosphere varies directly with the diameter of the source emission and reservoir pressure, and inversely with the temperature of the reservoir.The diameter of the source is the parameter that has the major effect on the extension of the explosive atmosphere, followed by the pressure and lastly the temperature of the reservoir.     

Single Au Atoms on the Surface of N-Free and N-Doped Carbon: Interaction with Formic Acid and Methanol Molecules

Topics in Catalysis - Formic acid and methanol are considered as liquid organic hydrogen carriers and could be produced sustainably from biomass or by CO2 hydrogenation using catalysts. The choice...     

Kinetics of ion-exchange-induced vitrification of glass-ceramics

Micro-Raman spectroscopy was applied to characterize the ion-exchange-induced vitrification of silicate glass-ceramics with lithium metasilicate crystalline phase. In parallel, the glass-ceramics vitrification was simulated on the base of the theory developed. Comparison of the data obtained with micro-Raman spectroscopy with the results of the simulation allowed revealing the kinetic parameters of vitrification process and evaluating the corresponding activation energies. These experimental approach and theory can be applied to other types of glass-ceramics.