Statistics for analytical chemistry

Gas-expanded liquids.

Pharmaceutical processing with supercritical carbon dioxide.

3.2.1. Linear F-Alkyl/H-Alkyl Diblocks 1720 3.2.2. Unsaturated Diblocks 1721 3.2.3. Branched Diblocks 1722 3.2.4. Diblocks with Heteroatoms 1723 3.2.5. Diblocks with Heavy Halogens 1724 3.3. Triblocks and Multiblocks 1724 3.3.1. FnHmFn Triblocks 1724 3.3.2. HmFnHm Triblocks 1725 3.3.3. Star-Shaped Triblocks 1725 3.3.4. Multiblocks and Polyaffine Compounds 1726 4. Basic Properties of (F-Alkyl)alkyl Diblocks 1726 4.1. The “Polarity” Issues“Apolar”, yet Dipolar 1726 4.2. Surfactant Properties 1727 4.2.1. Surfactant Effects of FnHm Diblocks at Interfaces with Air, Fluorocarbons, and Hydrocarbons 1728

Chemistry, physical chemistry, and uses of molecular fluorocarbon--hydrocarbon diblocks, triblocks, and related compounds--unique "apolar" components for self-assembled colloid and interface engineering.

Along more than a decade, R&D on supercritical fluid extraction (SFE) of vegetable matrices has been increasingly reported in the literature. Aiming at portraying the current state of this field and its evolution in terms of raw materials, products, modes of operation, optimization, modeling techniques, and closeness to industrial application, a large compilation of almost 600 essays from 2000 to 2013 has been deeply analyzed in order to unveil those indicators and their trends. Furthermore, strengths and weaknesses are identified, and some remarks that may drive upcoming research are provided. Globally, more than 300 species are reported in the literature, with prevalence of the extraction of seeds (28% of works) and leaves (17%). The main families of extracted compounds, cosolvents and operating conditions adopted are critically examined, being possible to conclude that researchers investigate many times working regions far from the optimum due to practical limitations or absence of experimental optimization. Current phenomenological, statistical and semi-empirical approaches are reviewed, along with scale-up studies, and economic analysis. In the whole, the most comprehensive picture over SFE of vegetable matrices is provided in this review, highlighting pertinent aspects and opportunities that may further consolidate the convincing route of this technology for the next years.

Supercritical fluid extraction of vegetable matrices: Applications, trends and future perspectives of a convincing green technology

The excess Cibbs energy of liquid mixtures may be predicted using group contribution models (f.ex. UNIFAC and ASOG), or it may be correlated using molecular models such as UNIQUAC. Group contribution models and the UNIQUAC model contain a combinatorial contribution which accounts for size- and shape-effects and a residual contribution which accounts for interactions among groups or molecules. A new expression for the combinatorial contribution is given which yields much improved predictions of the excess Gibbs energy of systems where the residual contribution may be expected to be zero (e.g., mixtures of aliphatic hydrocarbons). It is shown that it is advantageous to incorporate the new combinational expression into future modifications of the UNIFAC model.



On peut prevoir 1 energie d exces de Gibbs, dans le cas de melanges liquides, en employant des modeles de contribution de groupes (tels que UNIFAC et ASOG); on peut aussi etablir des correlations avec celle-ci au moyen de modeles moleculaires tels que UNIQUAC. Les modeles de contribution de groupes et le modele UNIQUAC impliquent une contribution com-binatoire, qui represente les effets des dimensions et de la forme, et une contribution residuelle qui represente les interactions entre les groupements ou les molecules. On presente une nouvelle expression relative a la contribution combinatoire, qui fournit des previsions bien meilleures de l'energie d'exces de Gibbs pour les systemes dans les quels on peut s'attendre a ce que la contribution residuelle soit nulle (exemple: melanges d'hydrocarbures aliphatiques). On demontre qu'il serait avantageux d'introduire la nouvelle expression combinatoire dans les modifications futures du modele UNIFAC.

On the Combinatorial Part of the UNIFAC and UNIQUAC Models

Supercritical fluid extraction is a potential technique for the purification of pharmaceutical products containing residual solvents. The solubilities of the drugs in supercritical carbon dioxide are being measured as part of a program in which the potential applications of this technology are being investigated. The solubilities of three inhibitors of inflammatory activity, Ketoprofen, Piroxicam, and Nimesulide, in supercritical CO2, measured using a dynamic saturation technique, are reported at pressures between 100 bar and 220 bar and at two temperatures:  312.5 K and 331.5 K. These chemicals have relatively high solubilities with values ranging from 4 × 10-6 to 15 × 10-4 mole fraction. The solubilities exhibit a clear dependence on the solvent density, and this has been used to provide a simple and precise correlation of the data.

Solubility of Anti-Inflammatory Drugs in Supercritical Carbon Dioxide

The manufacture of fine particles of two steroid drugsprogesterone and medroxyprogesterone acetatehas been investigated through the rapid expansion of supercritical solutions (RESS). The motivation was the production of particles with improved characteristics for use in the pharmaceutical industry. Solubility data for each drug in supercritical CO2 were measured prior to performing the RESS experiments as these data are essential for accurate experimental design. The solubility data were measured using a dynamic apparatus at pressures between 100 and 240 bar and at 313.1 and 333.1 K. Particles were manufactured by expanding a solution of supercritical CO2 saturated with drug through a micronozzle to pressures of 50 bar or less. A sufficient amount of particles was manufactured to allow particle characterization tests to be completed. Particle size, particle size distribution, and specific surface area were used as assessment measures to compare the product samples obtained in different experimental condit...

Particle production of steroid drugs using supercritical fluid processing

High pressure fluid phase equilibria : experimental methods and systems investigated (1978-1987)

High-pressure partition chromatography, a modification of the inverse gas chromatography technique, is presented as suitable technique for the study of the plasticization effect of carbon dioxide on the following polymers: poly(methyl methacrylate), polystyrene, and bisphenol A–polycarbonate. Polymers in the presence of a compressed gas or a supercritical fluid become plasticized; this means that their glass-transition temperatures (Tg's) can be lowered by 10s of degrees, which causes changes in their mechanical and physical properties. CO2-induced plasticization has an important impact on many polymer processing operations in which the Tg depressions of the polymers can be evaluated. The experimental results are discussed and compared with data available from literature for each polymer we considered. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2189–2193, 2003

Paolo Alessi

Papers

On the Combinatorial Part of the UNIFAC and UNIQUAC Models

Solubility of Anti-Inflammatory Drugs in Supercritical Carbon Dioxide

Particle production of steroid drugs using supercritical fluid processing

High pressure fluid phase equilibria : experimental methods and systems investigated (1978-1987)

Plasticization of polymers with supercritical carbon dioxide: Experimental determination of glass-transition temperatures