Comparison between different sheathless electrospray emitter configurations regarding the performance of nanoscale liquid chromatography-time-of-flight mass spectrometry analysis

Four different sheathless electrospray ionization (ESI) configurations were investigated for a nano liquid chromatography (LC) system. The studied configurations were: a column with an integrated emitter, with the ESI potential applied before or after the column, and a column with separate emitter, with the ESI voltage applied at a union before the emitter or at the emitter tip. The results indicates that the efficiency of the LC system is rather independent of the configuration when using 95 microm i.d. columns, acetic mobile phase and standard peptides as a sample. Introduction of post column dead volume seems not to be a critical issue at least with flow rates down to 600 nl/min.     

Al(III)-selective electrode based on newly synthesized xanthone derivative as neutral ionophore

The suitability of a xanthone derivative, 1-hydroxy-3-methyl-9H-xanthen-9-one (HMX) as a neutral ionophore for the preparation of a polyvinylchloride (PVC) membrane electrode for aluminum(III) ions was investigated. The prepared electrode exhibits a Nernstian response for Al³⁺ ions over a wide concentration range (1.0 × 10⁻⁶ to 1.6 × 10⁻¹ M) with a limit of detection 6.0 × 10⁻⁷ M. It has a relatively fast response time and can be used for at least three months without any considerable divergence in potentials. The proposed membrane electrode revealed very good selectivity for Al³⁺ ions over a wide variety of other cations and could be used at a working pH range of 3.0-8.5. It was used as an indicator electrode in potentiometric titration of aluminum ions with EDTA and in the determination of Al³⁺ in different real samples.     

Using empirical Eigenfunctions and Galerkin method to two‐phase transport models

In this article, we consider a nonlinear partial differential system describing two‐phase transports and try to recover the source term and the nonlinear diffusion term when the state variable is known at different profile times. To this end, we use a POD‐Galerkin procedure in which the proper orthogonal decomposition technique is applied to the ensemble of solutions to derive empirical eigenfunctions. These empirical eigenfunctions are then used as basis functions within a Galerkin method to transform the partial differential equation into a set of ordinary differential equations. Finally, the validation of the used method has been evaluated by some numerical examples. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 23: 456–474, 2007     

Interference of the electrospray voltage on chromatographic separations using porous graphitic carbon columns

The electrospray ionization (ESI) voltage is shown to interfere with liquid chromatographic separations performed with packed porous graphitic carbon (PGC) capillary columns. This interference is ascribed to the presence of an electric field over the conductive column in the absence of an earth point between the column and the ESI emitter. The current evolved alters the chromatographic behavior of the catecholamine metabolite 3-O-methyl-DOPA significantly, as both peak splitting and a dramatic decrease in the retention time were observed. Furthermore, the response from the mass spectrometer was decreased by 33% at the same time. A related compound, tyrosine, exhibited decreased retention times but no peak splitting, whereas no shifts in the retention times (or peak splitting) were seen for the less retained dopamine and noradrenaline. When the current through the PGC column was eliminated by the use of an earth point between the column and the ESI emitter, the chromatographic behavior of the column was found to return slowly to normal after hours of equilibration with 60 : 40 (v/v) methanol-ammonium formate buffer of pH 2.9. The behavior of the PGC column with and without the earth point was found to be highly reproducible during a period of 1 month. We propose that the effect of the ESI voltage on the chromatographic behavior of the PGC column is due to associated redox reactions affecting both the PGC particles and the analytes. It is concluded that (for analytical reasons), care should be taken to ensure that no current is flowing through the chromatographic system when interfacing PGC columns, and conducting parts in general, to ESI mass spectrometry.     

Effect of sintering temperature and soaking time on the magnetic properties and transmission behavior of nano crystalline Mg0.8Mn0.2Al0.1Fe1.9O4

Journal of Sol-Gel Science and Technology - In this study, Mg–Mn–Al ferrite with a chemical composition of Mg0.8Mn0.2Al0.1Fe1.9O4 was synthesized via the sol–gel auto-combustion...     

Numerical Simulation of Pressure-Swirl Spray Dispersion by Using Eulerian-Lagrangian Method

To gain a general understanding of atomization and sheet breakup processes, the interaction of pressure-swirl hollow-cone sprays and a quiescent medium was investigated computationally. The spray characteristics of Iso-octane (n-C₈H₁₈) with high pressure-swirl injector in the ambient conditions are modeled. The Linearized Instability Sheet Atomization (LISA) model has been used to describe the primary breakup processes of the spray. Sauter Mean Diameter, sheet thickness and exit velocity were computed as the results of primary breakup. Disintegration of large drops is simulated using Taylor analogy breakup (TAB) model in which the Rosin-Rammler distribution is used. Evaporation and collision models are deactivated in this study. The model considers the transient behavior of the pre-spray and steady-state behavior of the main spray for three various injection pressures and liquid mass flow rates. Qualitative and quantitative comparisons between the simulated and experimentally measured results were made. The numerical simulations can successfully demonstrate the spray characteristics, such as spray tip penetration, drop sizes and overall spray structure.     

Immobilized palladium nanoparticles on silica functionalized N-propylpiperazine sodium N-propionate (SBPPSP): catalytic activity evaluation in copper-free Sonogashira reaction

An efficient heterogeneous palladium catalyst system has been developed based on immobilization of Pd nanoparticles on silica-bonded N-propylpiperazine sodium N-propionate (SBPPSP) substrate. SBPPSP substrate can stabilize the Pd nanoparticles effectively so that it can improve their stability against aggregation. In addition, grafted piperazine species on to the silica backbone prevent the removing of Pd nanoparticles from the substrate surface. Transmission electron microscopy (TEM) of catalyst is shown the size of Pd nanoparticles, also it confirmed by particle size analyzer which shown the average size of 21 nm for Pd. The catalytic activity of these catalysts was investigated in the Sonogashira reaction. The catalyst could be recycled several times without appreciable loss in catalytic activity.     

Radioanalytical prediction of radiative capture in 99Mo production via transmutation adiabatic resonance crossing by cyclotron

In this study, the transmutation adiabatic resonance crossing (TARC) concept was estimated in ⁹⁹Mo radioisotope production via radiative capture reaction in two designs. The TARC method was composed of moderating neutrons in lead or a composition of lead and water. Additionally, the target was surrounded by a moderator assembly and a graphite reflector district. Produced neutrons were investigated by (p,xn) interactions with 30 MeV and 300 μA proton beam on tungsten, beryllium, and tantalum targets. The ⁹⁹Mo production yield was related to the moderator property, cross section, and sample positioning inside the distinct region of neutron storage as must be proper to achieve gains. Gathered thermal flux of neutrons can contribute to molybdenum isotope production. Moreover, the sample positioning to gain higher production yield was dependent on a greater flux in the length of thermal neutrons and region materials inside the moderator or reflector. When the sample radial distance from Be was 38 cm inside the graphite region using a lead moderator design, the production yield had the greatest value of activity, compared with the other regions, equal to 608.72 MBq/g. Comparison of the two designs using a Be target revealed that the maximum yield occurred inside the graphite region for the first design at 38 cm and inside the lead region for the second design at 10 cm. The results and modeling of the new neutron activator were very encouraging and seem to confirm that the TARC concept can be used for ⁹⁹Mo production in nuclear medicine.