ABSTRACT
Several mixtures of butyl acetate (BA) and an ionic liquid (1-methyl-3-octylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [C1C8Pyrro][NTf2], 1-octyl-pyridinium bis(trifluoromethylsulfonyl)imide, [C8Pyr][NTf2], 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide, [C1C4Im][NTf2] or 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide, [C1C8Im][NTf2]) have been characterized by measuring density, viscosity and conductivity, from pure BA to pure ILs at 298.15 K. The ionicity of these mixtures has been determined on the basis of electrical conductivity and NMR spectroscopy. IR spectra of these mixtures were used to examine the interactions between ions. In parallel, Pt(iv) was extracted from the acidic aqueous phase towards mixtures of BA and [C1C8Im][NTf2] over the entire composition range. A drastic modification in the distribution coefficient of Pt(iv) was observed at ca xAB = 0.8. A drop was also observed in the ionicity of the extracting phase (IL + BA) at a similar composition. The variation of the distribution coefficient is ascribed to changes in the interactions in the mixtures, which in turn could induce changes in the extraction mechanism.
ABSTRACT
The heat of dissolution of cellulose in one imidazolium acetate ionic liquid was determined experimentally. The value of -132 ± 8 J g(-1) indicates that the dissolution is exothermal thus confirming energetically favourable cellulose-ionic liquid interactions but indicating that an increase in temperature does not thermodynamically favour the dissolution process.
ABSTRACT
In the context of trans-dermal drug delivery it is very important to have mechanistic insight into the barrier function of the skin's stratum corneum and the diffusion mechanisms of topically applied drugs. Currently spectroscopic imaging techniques are evolving which enable a spatial examination of various types of samples in a dynamic way. ATR-FTIR imaging opens up the possibility to monitor spatial diffusion profiles across the stratum corneum of a skin sample. Multivariate data analyses methods based on factor analysis are able to provide insight into the large amount of spectroscopically complex and highly overlapping signals generated. Multivariate target factor analysis was used for spectral resolution and local diffusion profiles with time through stratum corneum. A model drug, 4-cyanophenol in polyethylene glycol 600 and water was studied. Results indicate that the average diffusion profiles between spatially different locations show similar profiles despite the heterogeneous nature of the biological sample and the challenging experimental set-up.
Subject(s)
Phenols/analysis , Skin Absorption , Spectroscopy, Fourier Transform Infrared/methods , Analysis of Variance , Diffusion , Drug Delivery Systems , Multivariate Analysis , Phenols/chemistry , Polyethylene Glycols/chemistry , Water/chemistryABSTRACT
Samples resulting from reaction of TiO(2) with octyltriethoxysilane, developed using a supercritical carbon dioxide procedure, have been studied by infrared and Raman spectroscopies and thermogravimetric analysis. Different reaction conditions have been applied to the preparation of samples in order to study the influence of experimental factors on the sample properties. Vibrational techniques have first been used to verify the presence of silanized structures on the surface of TiO(2) through the detection of specific bands characteristic of the Si-O-Si cross-linking. Thermogravimetric profiles consisting of weight loss values as a function of temperature have been analyzed by principal component analysis to extract information about the characteristics of the linkage between silane and TiO(2) as well as the thermal stability of the prepared materials. The mathematical treatment of data has provided conclusions on the properties of the samples and analogies and differences with respect to the commercial material.
ABSTRACT
We have investigated the state of aggregation in supercritical tert-butanol (T = 523 K,0.05 < rho < 0.4 g cm(-3)) by means of vibrational spectroscopies (infrared and Raman) and molecular-dynamics (MD) simulations. A quantitative band shape analysis of the spectra associated with the OH stretching mode of tert-butanol has been done using activities computed by ab initio calculations on small clusters. This allows us to determine the degree of hydrogen bonding and populations of oligomers. These latter quantities have been derived from MD simulations and very consistent results are found with experiments. These results show that hydrogen bond still exist in supercritical tert-butanol and that the fluid mainly consists of oligomers smaller than tetramers.
