Lorenzo Tassi

Adulteration of the anthocyanin content of red wines: perspectives for authentication by Fourier transform-near infrared and 1H NMR spectroscopies.

In the Italian oenological industry, the regular practice used to naturally increase the colour of red wines consists in blending them with a wine very rich in anthocyanins, namely Rossissimo. In the Asian market, on the other hand, anthocyanins extracted by black rice are frequently used as correctors for wine colour. This practice does not produce negative effects on health; however, in many countries, it is considered as a food adulteration. The present study is therefore aimed to discriminate wines containing anthocyanins originated from black rice and grapevine by using reliable spectroscopic techniques requiring minimum sample preparation. Two series of samples have been prepared from five original wines, that were added with different amounts of Rossissimo or of black rice anthocyanins solution, until the desired Colour Index was reached. The samples have been analysed by FT-NIR and (1)H NMR spectroscopies and the resulting spectra matrices were subjected to multivariate classification. Initially, PLS-DA was used as classification method, then also variable selection/classification methods were applied, i.e. iPLS-DA and WILMA-D. The classification with variable selection of NIR spectra permitted to classify the test set samples with an efficiency of about 70%. Probably these not excellent performances are due to the matrix effect, together with the lack of sensitivity of NIR with respect to minor compounds. On the contrary, very satisfactory results were obtained on NMR spectra in the aromatic region between 6.5 and 9.5 ppm. The classification method based on wavelet-based variables selection, permitted to reach an efficiency in validation greater than 95%. Finally, 2D correlation analysis was applied to FT-NIR and (1)H NMR matrices, in order to recognise the spectral zones bringing the same chemical information.

Durum wheat adulteration detection by NIR spectroscopy multivariate calibration

In the present work, we explored the possibility of using near-infrared spectroscopy in order to quantify the degree of adulteration of durum wheat flour with common bread wheat flour. The multivariate calibration techniques adopted to this aim were PLS and a wavelet-based calibration algorithm, recently developed by some of us, called WILMA. Both techniques provided satisfactory results, the percentage of adulterant present in the samples being quantified with an uncertainty lower than that associated to the Italian official method. In particular the WILMA algorithm, by performing feature selection, allowed the signal pretreatment to be avoided and obtaining more parsimonious models.

Coordinating ability of methylpiperidine dithiocarbamates towards platinum group metals

Abstract New rhodium(III), iridium(III), palladium(II) and platinum(II) dithiocarbamate complexes of the types M(Rdtc)3 and M(Rdtc)2 (Rdtc = 2-, 3- and 4-methylpiperidine dithiocarbamate) have been prepared and characterized by chemical analyses, conductance measurements, electronic and IR spectral studies, magnetic measurements and thermal analyses (TG and DTG techniques). From the electronic absorption spectra the values of the ligand field parameters were determined; the nephelauxetic parameters are indicative of a strong covalency in the metal-ligand bond. All the complexes here reported are diamagnetic and nonconducting both in the solid state and in DMF solution.

Ethane-1,2-diol–2-methoxyethanol solvent system. Dependence of the relative permittivity and refractive index on the temperature and composition of the binary mixture

The extrathermodynamic parameters, relative permittivity (Iµr) and refractive index (n), have been measured for ethane-1,2-diol–2-methoxyethanol binary mixtures over the entire composition range, at various temperatures ranging between –10 and 80 °C. For this system, as far as for many solvent–cosolvent systems which are useful for analytical and electrochemical applications, the properties cited above are continuous but not linear functions of the binary composition.Various equations have been applied in order to establish the best regression models for the relationship y=f(X), where X is the composition of the mixture. On the whole, minima occurred in the excess function (IµE), showing the existence of various solvent–cosolvent complexes of different stoichiometric ratios (2 : 1, 1 : 1 or 1 : 2) and of different thermostabilities, which may be interpreted in terms of moderate interactions such as dipolarity, polarizability and hydrogen bonding between the mixed solvents. Among the above complexes, the ethane-1,2-diol–2-methoxyethanol 1 : 2 adduct is suggested to be the true ‘limiting mixture’, on the borderline between the types of behaviour typical of the two pure solvents. Furthermore, empirical patterns in the refractive index were used to scrutinize the most important mixing rules in order to determine the properties of the mixture on the basis of those of its pure components.

Density, Refractive Index, and Related Properties for 2-Butanone + n-Hexane Binary Mixtures at Various Temperatures

Density refractive index n and the related properties molar volume V and molar refraction R have been investigated for 2-butanone + n-hexane liquid binary mixtures over the entire composition range and a wide range of temperatures. Some well-known relationships have been applied to study the temperature and composition dependence of the measured and derived quantities. Furthermore, the deviations of the respective excess properties VE, nE, and RE have been examined, with the aim of identifying particular intermolecular interaction patterns responsible for the macroscopic behavior of these binary mixtures. The results have been interpreted on the basis of structural and geometric effects between the components.

Preparation, properties and reactivity of gold complexes with some heterocyclic dithiocarbamates as ligands

Abstract The syntheses, properties and reactivity of the gold complexes AuRdtc, Au(RdtC)3, Au(Rdtc)2X and Au(RdtC)X2 (X = Cl, Br; Rdtc = piperidine-, morpholine-, thiomorpholine-, piperazine-, N-methylpiperazine-, N-phenylpiperazine- and 4-phenyl-piperidinedithiocarbamate) are reported. Elemental analysis, electrical conductance measurements, spectral (electronic and IR), magnetic susceptibility and thermogravimetric studies were used for characterization. The dithiocarbamato ligands exhibit both bidentate behaviour acting as S,S′-donors and monodentate behaviour acting as S-donors, depending on the type of the complex. The diamagnetic behaviour confirms the low-spin d8 configuration for Au(III) complexes and some metal-ligand and metal-halide stretches have been assigned.

Density and volumetric properties of ethane-1,2-diol + di-ethylen-glycol mixtures at different temperatures

Abstract The density of the ethane-1,2-diol (ED)+di-ethylen-glycol (DEG) binary mixtures has been measured at different temperatures over the complete composition range. The experimental measurements have been used to check the validity of relationships accounting for the dependence of the density on temperature and composition, useful to obtain interpolated values in the correspondence of the experimental data gaps. Starting from the primary data, some derived quantities, such as partial molar volumes, excess and partial excess molar volumes, have been obtained. In these mixtures, VE presents an S-shaped dependence on composition at each temperature, showing negative values in the ED rich-region and positive values at the opposite extreme. The results are compared and discussed to get light to the changes in molecular association and structural effects in this solvent system.

N,N-Dimethylformamide–2-methoxyethanol solvent system. Densities and excess molar volumes at various temperatures

Densities (ρ) have been measured for N,N-dimethylformamide (1), 2-methoxyethanol (2), and for nine binary mixtures covering the whole miscibility field (0 ⩽X1⩽ 1) in the temperature range –10–+80 °C. The experimental data were used to test some empirical equations of the type ρ=ρ(t), ρ=ρ(X1) and ρ=ρ(t, X1). Furthermore, the excess volumes (VE) for these binaries have been examined and discussed at all the investigated temperatures in terms of the influence of interactions between unlike molecules.The VEvs. X1 plots suggest the presence of some stable adducts, having N,N-dimethylformamide: 2-methoxyethanol stoichiometric ratios of 1 : 2 and 1 : 1 depending on the temperature.

Densities and excess molar volumes of binary mixtures containing 1,2-dichloroethane + 2-methoxyethanol or 1,2-dimethoxyethane at different temperatures

Abstract Density of the 1,2-dichloroethane + 2-methoxyethanol or 1,2-dimethoxyethane binary mixtures have been measured at different temperatures over the complete composition range. Several experimental measurements have been used to check the validity of the relationships accounting for the dependence of the density on temperature and composition, useful to obtain interpolated values in correspondence of the experimental data gaps. Starting from the primary data, some derived quantities, such as partial molar volumes, excess and partial excess molar volumes, have been obtained. In these mixtures, V E is always positive for DCE + ME binaries, while an S-shaped dependence on composition at each temperature is obtained in DCE + DME system, showing positive values in the DCE rich-region and negative values at the opposite extreme. The results are compared and discussed to shed some light to the changes in molecular association and structural effects in these binary solvent systems.

Dielectric behaviour of the 2-methoxyethanol–1,2-dimethoxyethane solvent system

The static relative permittivity at various temperatures ranging from –10 to +80 °C has been measured for 2-methoxyethanol, 1,2-dimethoxyethane and nine mixtures covering the whole miscibility field expressed by the mole fraction of 2-methoxyethanol (0 ⩽X1⩽ 1).Equations describing the dependence of the relative permittivity on temperature [Iµ=Iµ(T)], and binary composition [Iµ=Iµ(X1)], have been checked. Furthermore, a single function Iµ=Iµ(T, X1) has been obtained by combining the previously cited monovariant equations. As a rule, the calculated values agree very well with the experimental ones.The excess extrathermodynamic parameter IµE, which provides much useful information about the possibility of forming solvent–cosolvent complexes is briefly discussed. This fact has been interpreted on the basis of specific interactions of any kind between different molecules, taking into account geometric effects and steric hindrances.