Dual analyte flow injection fluorescence immunoassays using thiophilic gel reactors and synchronous scanning detection

Heterogeneous fluorescence immunoassays have been automated using flow injection manifolds incorporating thiophilic gel solid phase reactors to separate antibody-bound and unbound analyte molecules. Antibody elution is achieved by changes in ionic strength, thus allowing the use of pH sensitive fluorescent labels. This facilitates the development of dual analyte systems, in which two competitive immunoassays with separate labels are monitored in parallel. Detection of the fluorophores by high speed synchronous fluorescence scanning while the flow is briefly stopped utilises either one synchronous interval which detects both fluorophores, or two separate scans at different wavelength intervals, one for each fluorophore. Simultaneous analyses of serum albumin and transferrin exemplify these novel approaches. Spectroscopic interferences are very small, analyte recoveries are close to 100%, with a relative standard deviation of 5-6% and a sampling rate of 20 h-1.     

Sharpless asymmetric dihydroxylation of 5-aryl-2-vinylfurans: application to the synthesis of the spiroketal moiety of papulacandin D

[formula: see text] Using the Sharpless catalytic asymmetric dihydroxylation reaction on 5-aryl-2-vinylfurans, diols are produced in high enantioexcess. The resulting diols can be efficiently transformed into the spiroketal ring precursor of the antifungal compound papulacandin D. Stereoselective reduction of this precursor followed by a diastereoselective dihydroxylation completes the synthesis of a mannopyranoside isomer of a papulacandin derivative.     

Modulation effects in the electron spin echo of trans bis-(2,2,5,5-tetramethyl-3-imidazoline-3-oxide-1-oxyl-4-il) ethylene biradicals

Electron spin echo modulation effects have been investigated in trans bis(2,2,5,5-tetramethyl-3-imidazoline-3-oxide-1-oxyl-4-il) ethylene biradicals involving ¹⁴N or ¹⁵N nuclei in different positions. The modulation frequencies are shown to be the nitrogen nuclear transition frequencies in radical fragments at m_S = 0 of a triplet electronic spin. Quadrupole splitting parameters for these nitrogen nuclei have been determined.     

Radiochemical Study of Reactions of Diethylsilylium Ions with Dibutyl Ether in the Gas and Liquid Phases

Reactions of diethylsilylium ions with dibutyl ether in the gas and liquid phases were studied radiochemically. These reactions, as those with benzene and alcohols, are accompanied by partial rearrangement of diethylsilylium ions into monoethylsilylium and dimethylsilylium ions. The extent of transformations of the (C₂H₅)₂SiT⁺ ions decreases in going from benzene to dibutyl ether, which is due to the higher energy of adduct formation with the ether, compared to benzene.     

Comparison of neutron activation analysis methods

This work shows that nuclear data and neutron flux parameters can be applied to calculate directly the elemental concentrations. Techniques for extracting neutron flux parameters pertaining to the irradiation positions and nuclear data pertaining to the isotopes concerned from measured reaction rates have been previously developed. This method is compared to the comparator and relative methods of activation analysis. The principles, advantages and disadvantages of each method and sources of errors are discussed. It also briefly discusses other factors such as accuracy and precision, sensitivity, detection limits and limit of quantitative determination. The three methods are applied to the analysis of five environmental reference materials. The concentrations of more than 20 elements are determined. The results show a good agreement with the certified and/or literature values.     

Effects of injector geometry and sample matrix on injection and sample loading in integrated capillary electrophoresis devices

The double-T injector design employed in many microchip capillary electrophoresis devices allows for the formation of very small (50-500 pL) sample plugs for subsequent analysis on-chip. In this study, we show that sample plugs formed at the channel junction can be geometrically defined. The channel width and injector symmetry prove to be of great importance to good performance. A unique pushback of solvent into the side channels can be induced when the side channels have a very low resistance to flow, and this helps to better define the injected sample plug. Samples and running buffers of differing ionic strength (e.g., 10 mM KCl buffer and 20 mM KCl sample) can yield widely variable results in terms of plug shape and amount injected (variations of 1.5 to 10x). Applying bias voltages to all the intersecting channels aids in controlling the plug shape. However, when the ionic strengths of buffer and sample are not matched, the actual amount injected (up to 10x variations) can be inconsistent with the appearance of the plug formed in the injector (up to only 30 % variations). Operating at constant pH and ionic strength produced the most consistent results. This report examines the effects of altering the injector geometry and solution ionic strengths, and presents the results of using bias voltages to control plug formation. The observed results should provide a benchmark for modeling of the fluid dynamics in channel intersections.     

The application of multivariate techniques to data from spanish glass-making objects from the Roman Era

Three multivariate techniques (principal components analysis, correspondence factor analysis and spectral map analsis) are applied to x-ray fluorescence data from glass-making objects from the 5th century AD found in Tarragona (Tarraco in the Roman Empire). The information obtained by displaying th eobjects and variables in each reduced factor space is compared. The presence of redundant information is shown. The visualization of groups of objects and of the relationship between objects and variables allows the formulation of hypotheses concerning the origin of the samples and the presence of local glassworks.     

The effect of clusters and heterogeneous reactions on non-equilibrium plasma flue gas cleaning

Theoretical investigation of the effect of molecular clusters and aerosol particles on non-equilibrium plasma flue gas cleaning was made in this paper. Two types of heterogeneous reactions in aerosol and clusters are considered. It was shown that in both cases these reactions are essential in the evaluation of chemical composition. As a result of theoretical approach and modelling, the optimum regime of plasma generation for essential decreasing of purification energy cost was established.     

Ion-Molecular Reactions of Diethylsilylium Ions with Alcohols in the Gas Phase

Radiochemistry was used to study reaction of tritium-labeled diethylsilylium ions with alcohols in the gas phase. The reaction involves both rearrangement of the diethylsilylium ions and isomerization of the substituent in the substrate. The hydroxyl hydrogen of the alcohol and the tritium atom of the diethyl-silylium ion undergo exchange which, however, is less vigorous that in the case of the monoethylsilylium ion. A possible reaction mechanism is proposed.     

Cycloaddition of fluorinated oxazoles

Cycloaddition reactions of polyfluorinated 1,3-oxazoles with cyclic and acyclic alkenes were studied. The results of these reactions were interpreted using quantum chemical calculations. An unusual product, viz., fluorine-containing acylpyrrole, was studied by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1630–1635, July, 2005.