Rosa Garriga

Densities and viscosities of binary mixtures of butanone with butanol isomers at several temperatures

Densities and viscosities of 1-chlorobutane + 1-butanol, + 2-methyl-1-propanol, + 2-butanol, or + 2-methyl-2-propanol were measured at several temperatures between 288.15 K and 318.15 K. At each temperature, the experimental viscosity data were correlated by means of the McAllister biparametric equation. By using our previous thermodynamic measurements (VLE, HE), we have tested the Wei and Rowley nonparametric model at T = 298.15 K, obtaining average absolute deviations that are comparable to those calculated for the biparametric model.

Vapour pressures at several temperatures between 288.15 K and 323.15 K of di-n-propylether with 1-hexanol or 1-octanol. Application of the ERAS model

Abstract Vapour pressures of di- n -propylether+1-hexanol or +1-octanol were measured at several temperatures between 288.15 K and 323.15 K by a static method. Reduction of the vapour pressures to obtain activity coefficients and excess molar Gibbs free energies was carried out by Barkers method. G E , H E , and V E , at 298.15 K, are compared with predictions of the ERAS-model observing that the model reproduces acceptably the experimental behaviour.

Excess Gibbs free energies at seven temperatures and excess enthalpies and volumes at 298.15 K of butanone with 1-propanol or 2-propanol

Abstract Vapour pressures of butanone + 1-propanol or + 2-propanol at seven temperatures between 278.15 and 323.15 K were measured by a static method. Excess molar enthalpies and volumes were also measured at 298.15 K. Following Barkers method, the activity coefficients and the excess molar Gibbs free energies were fitted to the Wilson correlation. Mixtures containing 2-propanol show azeotropy with a minimum boiling temperature. The thermodynamic excess functions are discussed with respect to the molecular interactions and compared with those for binary mixtures containing the same alcohols with other solvents.

Excess Gibbs free energies at several temperatures and excess enthalpies and volumes at 298.15 K of butanenitrile with 2-methyl-1-propanol or 2-methyl-2-propanol

Abstract Vapour pressures of butanenitrile +2-methyl-1-propanol or +2-methyl-2-propanol at several temperatures between 278.15 and 323.15 K were measured by a static method. Excess molar enthalpies and volumes were also measured at T = 298.15 K. Reduction of the vapour pressures to obtain activity coefficients and excess molar Gibbs free energies was carried out by fitting the vapour pressure data to the Redlich-Kister correlation according to Barkers method. Azeotropic mixtures with a minimum boiling temperature were observed over the whole temperature range, except for 2-methyl-2-propanol at T = 323.15 K.

Graphene oxide as sensitive layer in Love-wave surface acoustic wave sensors for the detection of chemical warfare agent simulants

A Love-wave device with graphene oxide (GO) as sensitive layer has been developed for the detection of chemical warfare agent (CWA) simulants. Sensitive films were fabricated by airbrushing GO dispersions onto Love-wave devices. The resulting Love-wave sensors detected very low CWA simulant concentrations in synthetic air at room temperature (as low as 0.2 ppm for dimethyl-methylphosphonate, DMMP, a simulant of sarin nerve gas, and 0.75 ppm for dipropylene glycol monomethyl ether, DPGME, a simulant of nitrogen mustard). High responses to DMMP and DPGME were obtained with sensitivities of 3087 and 760 Hz/ppm respectively. Very low limit of detection (LOD) values (9 and 40 ppb for DMMP and DPGME, respectively) were calculated from the achieved experimental data. The sensor exhibited outstanding sensitivity, good linearity and repeatability to all simulants tested. The detection mechanism is here explained in terms of hydrogen bonding formation between the tested CWA simulants and GO.

Isothermal vapour-liquid equilibrium at eight temperatures and excess functions at 298.15 K of di-n-propylether with 1-propanol or 2-propanol

Vapour pressures of di-n-propylether + 1-propanol or + 2-propanol at eight temperatures between 278.15 and 323.15 K were measured by a static method. Excess molar enthalpies and volumes were also measured at 298.15 K. Following Barkers method, the activity coefficients and the excess molar Gibbs free energies were fitted to the Wilson equation. Azeotropic mixtures with a minimum boiling temperature were observed over the whole temperature range.

Fluorescence detection by intensity changes for high-performance thin-layer chromatography separation of lipids using automated multiple development

Changes in emission of berberine cation, induced by non-covalent interactions with lipids on silica gel plates, can be used for detecting and quantifying lipids using fluorescence scanning densitometry in HPTLC analysis. This procedure, referred to as fluorescence detection by intensity changes (FDIC) has been used here in combination with automated multiple development (HPTLC/AMD), a gradient-based separation HPTLC technique, for separating, detecting and quantifying lipids from different families. Three different HPTLC/AMD gradient schemes have been developed for separating: neutral lipid families and steryl glycosides; different sphingolipids; and sphingosine-sphinganine mixtures. Fluorescent molar responses of studied lipids, and differences in response among different lipid families have been rationalized in the light of a previously proposed model of FDIC response, which is based on ion-induced dipole interactions between the fluorophore and the analyte. Likewise, computational calculations using molecular mechanics have also been a complementary useful tool to explain high FDIC responses of cholesteryl and steryl-derivatives, and moderate responses of sphingolipids. An explanation for the high FDIC response of cholesterol, whose limit of detection (LOD) is 5 ng, has been proposed. Advantages and limitations of FDIC application have also been discussed.

Isothermal vapour–liquid equilibrium at several temperatures and excess functions at 298.15 K of butanone with 2-methyl-1-propanol or 2-methyl-2-propanol

Abstract Vapour pressures of butanone+2-methyl-1-propanol or +2-methyl-2-propanol at several temperatures between 278.15 and 323.15 K were measured by a static method. Excess molar enthalpies and volumes for 2-methyl-1-propanol were also measured at 298.15 K. Reduction of the vapour pressures to obtain activity coefficients and excess molar Gibbs free energies was carried out by fitting the vapour pressure data to the Redlich–Kister correlation according to Barkers method. It is made as a comparison of the thermodynamic properties of mixtures of alcohols in butanone and n-hexane, and the results are qualitatively discussed.

Changes in fluorescent emission due to non-covalent interactions as a general detection procedure for thin-layer chromatography.

Changes in fluorescence emission due to non-covalent analyte-fluorophore interactions in silica gel plates are studied and used as a general detection procedure for thin-layer chromatography (TLC). The presence of the analyte modifies the microenvironment of the fluorophore and thus changes the balance between radiative (k(r)) and non-radiative (k(nr)) emission constants. A model is proposed for analyte-fluorophore induced electrostatic interactions, which depend on analyte polarizability and are responsible for fluorescence enhancements. As consequence of these induced interactions, the analyte creates an apolar environment that prevents non-fluorescent decay mechanisms, decreasing k(nr). On the other hand, the effect of an increase in refractive index on k(r) is investigated, as it contributes to some extent to fluorescence enhancements in silica gel medium. Changes in fluorescence emission should be regarded as a general property of fluorophores in the presence of analytes, and criteria that fluorophores should meet to be used as sensitive TLC probes are discussed here.

Thermodynamic properties of binary mixtures containing n-alkylamines. II. Isothermal vapour-liquid equilibrium and excess molar enthalpy of n-alkylamine + ethylbenzene mixtures. Measurement and analysis in terms of group contributions

Abstract Molar excess enthalpies, H E , at 303.15 K and atmospheric pressure, of n -propyl-, n -butyl-, n -pentyl-, n -octyl- or n -decylamine+toluene, as well as the isothermal vapour–liquid equilibria, VLE, of n -butylamine+toluene and of n -butylamine+benzene at 298.15 K have been determined. These experimental results, along with the data available in the literature on molar excess Gibbs energies, G E , activity coefficients at infinite dilution, γ i ∞ , and molar excess enthalpies, H E , for n -alkylamine+toluene mixtures are examined on the basis of the DISQUAC group contribution model. The modified UNIFAC is also used to describe the mixtures.