Simple extraction method and gas chromatography-mass spectrometry in the selective ion monitoring mode for the determination of phenols in wine

The concentrations of 22 components of wine, including most of those that have been shown to possess significant biological properties, have been determined by a fast and simple analytical method based on gas chromatography with mass spectrometric detection in the selective ion monitoring mode (GC/MS-SIM). The procedure involves an easy liquid-liquid extraction and derivatization methods of flavanols, phenols and carboxylic acid, using a very small wine volume. The average recovery (Rcv) ranged from 73 to 107% and linear regression coefficients (r(2)) were in a range of 0.981or=0.999. The GC/MS-SIM technique gives good specificity and sensitivity, and can therefore be suitable for routine monitoring of the concentration of individual phenolic antioxidants during winemaking and the aging process.     

Sequential unsymmetrical aryl coupling of o-substituted aryl iodides with o-bromophenols and reaction with olefins: palladium-catalyzed synthesis of 6H-dibenzopyran derivatives

Dibenzopyran derivatives are prepared by palladium- and norbornene-catalyzed reaction of aryl iodides, o-substituted with electron-releasing substituents, o-bromophenols, and activated alkenes.     

Dynamic HPLC on chiral stationary phases: a powerful tool for the investigation of stereomutation processes

Dynamic HPLC on enantioselective stationary phases has become a well-established technique to investigate chiral molecules with internal motions that result in stereoinversion and occur on the time scale of the separation process. Kinetic parameters for the on-column interconversion phenomena can be extracted from experimental peak profiles by computer simulation or by direct calculation methods. The technique has been used in a wide range of temperatures and is complementary in scope to dynamic NMR spectroscopy.     

A Quantitative Voronovskaya Formula for Mellin Convolution Operators

Here we give a quantitative Voronovskaya formula for a class of Mellin convolution operators of type

A note on triangulated monads and categories of module spectra

Consider a monad on an idempotent complete triangulated category with the property that its Eilenberg–Moore category of modules inherits a triangulation. We show that any other triangulated adjunction realizing this monad is ‘essentially monadic’, i.e. becomes monadic after performing the two evident necessary operations of taking the Verdier quotient by the kernel of the right adjoint and idempotent completion. In this sense, the monad itself is ‘intrinsically monadic’. It follows that for any highly structured ring spectrum, its category of homotopy (aka naïve) modules is triangulated if and only if it is equivalent to its category of highly structured (aka strict) modules.     

The design of efficient and selective routes to a key 1,4-cis-substituted cyclohexylamide intermediate

This Letter describes the synthetic challenges in synthesising key 1,4-cis-substituted cyclohexylamide intermediate 1 for our research programme. Five different routes address the major issues of selectivity to afford the cis product in isomerically pure form and in high yield. Major purification issues were also encountered upon scaling some of the routes. The merits of the diverse routes are assessed and the reasoning given for which one was ultimately used for large-scale synthesis of 1.     

Surface structure and properties of poly-(ethylene terephthalate) hydrolyzed by alkali and cutinase

This study was aimed at comparatively investigating the hydrolysis of crystalline and amorphous poly-(ethylene terephthalate) films by alkali and cutinase. Changes of surface properties were investigated by FTIR spectroscopy (ATR mode). The A₁₃₄₁/A₁₄₁₀ and I₁₁₂₀/I₁₁₀₀ absorbance ratios, and the full width at half maximum of the carbonyl stretching band (FWHM₁₇₁₅) were used to evaluate the polymer crystallinity and its changes upon hydrolysis. The effect of different treatments on chain orientation was evaluated by calculating R ratios of appropriate bands. The spectroscopic indexes showed that both alkali and enzyme treatments induced structural and conformational rearrangements with a consequent increase in crystallinity in both amorphous and crystalline films. The crystalline PET film was modified more strongly by alkali than by cutinase, while the opposite occurred for the amorphous one. The trend of the water contact angle (WCA) clearly indicates that alkali is more effective than cutinase in enhancing hydrophilicity of PET films and that the effect is stronger on amorphous than on crystalline films. The values of WCA correlate well with the FTIR indexes calculated from the spectra of hydrolyzed crystalline PET films. The mechanism of the surface hydrolysis of PET by alkali and cutinase is discussed.     

Theoretical insights on O2 and CO adsorption on neutral and positively charged gold clusters

With the aim of understanding the elementary steps governing the oxidation of CO catalyzed by dispersed or supported gold nanoclusters, the adsorption of molecular species, such as O2 and CO, on model neutral and positively charged clusters (Au(n)(m+) n = 1, 9, and 13; m = 0, 1, and 3) has been studied using an ab initio approach. The computed structural and thermodynamic data related to the binding process show that molecular oxygen interacts better with neutral clusters, acting as an electron acceptor, while CO more strongly binds to positively charged species, thus acting as an electron donor.     

The optimal compliance problem for thin torsion rods: A 3D-1D analysis leading to Cheeger-type solutions

We consider the variational problem which consists in minimizing the compliance of a prescribed amount of isotropic elastic material placed into a given design region when it is subjected to a given load. We perform the asymptotics of this problem when the design region is a straight cylinder with infinitesimal cross section. The results presented in this Note concern the pure torsion regime and state the existence of optimal shapes for the limit problem. When the filling ratio tends in turn to zero, these optimal shapes concentrate on the boundary of the Cheeger set of the section of the design region.     

Characterisation of natural indigo and shellfish purple by mass spectrometric techniques

Two analytical methods based on mass spectrometry were used in the characterisation of constituents of natural indigo prepared from the leaves of Indigofera tinctoria, and of shellfish purple prepared from the hypobranchial glandular secretions of Murex trunculus, following old recipes. On-line pyrolysis gas chromatography in the presence of hexamethyldisilazane followed by mass spectrometric analysis (Py-silylation/GC/MS), and direct exposure mass spectrometry (DE-MS), were used. Extensive fragmentation of indigoid dyes was obtained by Py-silylation/GC/MS. The following molecular markers were highlighted, which are useful for identification purposes: 1,2-dihydro-3H-indol-3-one for indigoid dyes, 1,3-dihydro-2H-indol-2-one for indirubine, and 6-bromo-1,2-dihydro-3H-indol-3-one for shellfish purple. Using DE-MS, 6,6'dibromoindigotine, monobromoindigotine and indigotine were identified as the main components, and the presence of tyrindoxyl, one of the dye precursors, was also assessed.