Liquid chromatographic method for the analysis of tocopherols in malt sprouts with supercritical fluid extraction.

A simple, specific and sensitive high-performance liquid chromatographic method has been developed for the determination of tocopherols in malt sprouts. A supercritical fluid extraction (SFE) procedure was used to isolate tocopherols from the vegetal matrix before quantitative analysis. The analytes were separated on a Zorbax reversed-phase column using methanol-water as mobile phase and quantified by measuring its fluorescence at lambda(em)=328 nm after excitation of the analytes at lambda(exc)=303 nm. The limits of detection for alpha-, gamma- and delta-tocopherols were 0.04, 0.05, and 0.05 microg/ml, respectively. The calibration graphs of the method were linear from 0.1 to 1.5, 0.2 to 2.5, and 0.2 to 2.0 microg/ml, for alpha-, gamma- and delta-tocopherols, respectively. This SFE and HPLC procedure is simple, precise and accurate for the determination of tocopherols in malt sprouts.     

Helmholtz conditions,covariance, and invariance identities

This paper is concerned with the problem of finding a multiplier matrixg which converts a prescribed system of second-order ordinary differential equations to the Euler-Lagrange form. Sufficient conditions for the existence of a multiplier matrix are given in the form of an infinite system of linear algebraic equations, provided the entries ofg may be regarded as components of a (0, 2) symmetric tensor field. As an application, conditions for the local existence of a metric tensor compatible with a given torsion-free connection are deduced.     

Equiconvergence Theorems for Sturm Liouville Expansions and Sets of Divergence for Bochner Riesz Means in Sobolev Spaces

We state some equiconvergence results between Bochner Riesz means of expansions in eigenfunctions of suitable Sturm Liouville operators. Then we determine the Hausdorff dimension of the divergence set of Bochner Riesz means of radial functions in Sobolev classes on Euclidean and non Euclidean spaces.     

The Michelson interferometer

The apparatus that Michelson brought to the BIPM in 1892 to determine the value of the metre in luminous wavelengths has generated a vast family of instruments typically used for length measurement. Looking at them from this point of view teaches us a lot about the characteristics of the Michelson interferometer that make it specially convenient for Fourier transform spectroscopy (FTS). Michelson himself used the principle of the FTS to check the monochromaticity of various spectral lines. He was looking for a good standard of length, hence he did not care so much about the general problem of spectroscopy. Furthermore, he was limited to the parameter that he called the visibility of the fringes, i.e. the modulus of the Fourier transform of the spectral distribution, in fact the only parameter that the naked eye can roughly estimate, besides the fringe spacing. As he counted only up to 1212 fringes, and thereafter used a stepping process by optical addition, he did not worry about the optical defects that impair direct interferometric measurement of long distances. A few technological improvements have made the fringe-counting technique the current way of measuring length. It is shown that the analysis required for accurate length measurements with a Michelson interferometer is similar to the one required to make accurate FTS.     

Water—Trifluoroethanol Mixtures: Some Physicochemical Properties

The-physicochemical properties of water—2,2,2 trifluoroethanol mixtures havebeen investigated, at 25°C, by density, viscosity, surface tension, and relativepermittivity. An analysis based on the Kirkwood theory for the dielectric polarizationof mixtures has been performed and the g correlation factor has been relatedto the occurrence of hydrogen bonding networks. Data on the above systemhave been analyzed and compared to data on water—ethanol mixtures, to obtaininformation on the role that partial fluorination plays in the interactions of alcoholswith water molecules. As inferred from excess properties, nonideality contributionsare smaller than in the corresponding water—ethanol solutions. Accordingly,the extension of hydrogen bond networks and/or van der Waals contributions tothe overall system stability are less significant than in simple alcohols.     

Laser induced breakdown spectroscopy on meteorites

The classification of meteorites when geological analysis is unfeasible is generally made by the spectral line emission ratio of some characteristic elements. Indeed when a meteorite impacts Earth's atmosphere, hot plasma is generated, as a consequence of the braking effect of air, with the consequent ablation of the falling body. Usually, by the plasma emission spectrum, the meteorite composition is determined, assuming the Boltzmann equilibrium. The plasma generated during Laser Induced Breakdown Spectroscopy (LIBS) experiment shows similar characteristics and allows one to verify the mentioned method with higher accuracy. On the other hand the study of Laser Induced Breakdown Spectroscopy on meteorite can be useful for both improving meteorite classification methods and developing on-flight techniques for asteroid investigation.

In this paper certified meteorites belonging to different typologies have been investigated by LIBS: Dofhar 461 (lunar meteorite), Chondrite L6 (stony meteorite), Dofhar 019 (Mars meteorite) and Sikhote Alin (irony meteorite).     

Cp*Rh(bpy)(H2O)]2+ as a coenzyme substitute in enzymatic oxidations catalyzed by Baeyer-Villiger monooxygenases

[Cp*Rh(bpy)(H2O)]2+ was applied as a flavin regenerating reagent in BVMO catalyzed oxidations of organic sulfides to chiral sulfoxides.     

Homogeneous immunoassay of atrazine in water by terbium-entrapping liposomes as fluorescent markers

Atrazine (Atr) was conjugated to mastoparan (Mast) cytolytic peptide; Mast-Atr derivative was used as cytolytic agent on liposomes trapping Tb/citrate complex. This was applied in a time-resolved fluoroimmunoassay for detection of Atr in water. The cytolytic activity was read by means of time-resolved fluorescence after adding an excess of dipicolinic acid (DPA). Tb/citrate-entrapping liposomes are easy to prepare, and the assay is carried out in a short incubation time and in a range between 10 pg and 100 ng. The procedure was applied to analyse samples taken from Adda River and from irrigation ditches in an agricultural area around the town of Lodi. Recovery in samples spiked with two different Atr concentrations was between 95 and 105%.     

Computing the (1)H NMR spectrum of a bulk ionic liquid from snapshots of car-parrinello molecular dynamics simulations.

We have investigated the performance of several computational protocols in predicting the NMR spectrum of a molecular ion in a complex liquid phase such as an ionic liquid. To do this, we computed the proton NMR chemical shifts of the 1-ethyl-3-methylimidazolium cation [emim](+) in [emim][Cl]. Environmental effects on the imidazolium ring proton chemical shifts are quite significant and must be taken into account explicitly. Calculations performed on the isolated imidazolium cation as well as on the [emim][Cl] ion pair grossly fail to reproduce the correct spacing between proton signals. In contrast, calculations performed on clusters extracted from the trajectory of a Car-Parrinello molecular dynamics simulation yield very good results.