Solubility Determination, Hansen Solubility Parameters and Thermodynamic Evaluation of Thymoquinone in (Isopropanol + Water) Compositions.

This article studies the solubility, Hansen solubility parameters (HSPs), and thermodynamic behavior of a naturally-derived bioactive thymoquinone (TQ) in different binary combinations of isopropanol (IPA) and water (H2O). The mole fraction solubilities (x3) of TQ in various (IPA + H2O) compositions are measured at 298.2-318.2 K and 0.1 MPa. The HSPs of TQ, neat IPA, neat H2O, and binary (IPA + H2O) compositions free of TQ are also determined. The x3 data of TQ are regressed by van't Hoff, Apelblat, Yalkowsky-Roseman, Buchowski-Ksiazczak λh, Jouyban-Acree, and Jouyban-Acree-van't Hoff models. The maximum and minimum x3 values of TQ are recorded in neat IPA (7.63 × 10-2 at 318.2 K) and neat H2O (8.25 × 10-5 at 298.2 K), respectively. The solubility of TQ is recorded as increasing with the rise in temperature and IPA mass fraction in all (IPA + H2O) mixtures, including pure IPA and pure H2O. The HSP of TQ is similar to that of pure IPA, suggesting the great potential of IPA in TQ solubilization. The maximum molecular solute-solvent interactions are found in TQ-IPA compared to TQ-H2O. A thermodynamic study indicates an endothermic and entropy-driven dissolution of TQ in all (IPA + H2O) mixtures, including pure IPA and pure H2O.

Σpider diagram: a universal and versatile approach for system comparison and classification: application to solvent properties.

Classification methods based on physico-chemical properties are very useful in analytical chemistry, both for extraction and separation processes. Depending on the number of parameters, several classification approaches can be used: by plotting two- or three-dimensional maps (triangles, cubes, spheres); by calculating comparison values for one system with reference to another one, i.e. the ranking factor F, or the Neue selectivity difference s(2); or with chemometric methods (principal component analysis-PCA or hierarchical cluster analysis-HCA). All these methods display advantages and drawbacks: some of them are limited by the number of studied parameters (e.g. three for triangle or sphere plots); others require a new calculation when changing the reference point (F; s(2)), while for chemometric methods (PCA, HCA), the relationships between the clusters and the physico-chemical properties are not always easily understandable. From previous studies performed in supercritical fluid chromatography for stationary phase classification on the basis of linear solvation energy relationships (LSER) including five parameters, we developed a classification map called the Σpider diagram. This diagram allows plotting in a two-dimensional map the location of varied systems, having as many parameters as the ones required getting a satisfactory classification. It can be three, five, eight, or any number. In the present paper, we apply this diagram, and the calculation mode to obtain this diagram, to different solvent classifications: Snyder triangle, solvatochromic solvent selectivity, Hansen parameters, and also to LSER Abraham descriptors and COSMO-RS parameters. The new figure based on Snyder data does not change the global view of groups, except by the use of corrected data from literature, and allows adding the polarity value onto the map. For the solvatochromic solvent selectivity, it leads to achieve a better view of solvents having no acidic character. For Hansen parameters, the "flattening" of the spherical view down to a single plane could be found easier to use. For COSMO-RS and with Abraham descriptor, a more subtle classification is achieved, mainly due to the use of five parameters instead of three. A strong reversed correlation is established between the Rohrschneider polarity P' and the normalized V (molecular volume) parameter. The study of the location of solvents used for reversed-phase liquid chromatography and the Arizona system for counter-current chromatography is discussed, as well as the replacement of unsafe solvents by greener ones, or the use of these classifications for the study of compound solubility. Besides, this paper also shows the ability to the spider diagram to plot on a single plane three axes from principal component analyses.

Intercomparison of measurement techniques for black or elemental carbon under urban background conditions in wintertime: influence of biomass combustion.

A generally accepted method to measure black carbon (BC) or elemental carbon (EC) still does not exist. An earlier study in the Vienna area comparing practically all measurement methods in use in Europe gave comparable BC and EC concentrations under summer conditions (Hitzenberger et al., 2006a). Under summer conditions, Diesel traffic is the major source for EC or BC in Vienna. Under winter conditions, space heating (also with biomass as fuel) is another important source (Caseiro et al., 2007). The present study compares the response of thermal methods (a modified Cachier method, Cachier et al., 1989; a thermal-optical method, Schmid et al., 2001; and two thermal-optical (TOT) methods using Sunset instruments, Birch and Cary, 1996 and Schauer et al., 2003) and optical methods (a light transmission method, Hansen et al., 1984; the integrating sphere method, Hitzenberger et al., 1996; and the multiangle absorption photometer MAAP, Petzold and Schönlinner, 2004). Significant differences were found between the TOT methods on the one hand and all other methods on the other. The TOT methods yielded EC concentrations that were lower by 44 and 17% than the average of all measured concentrations (including the TOT data). The largest discrepancy was found when the contribution of brown carbon (measured with the integrating sphere method) was largest.

Recent advances in analytical determination of thalidomide and its metabolites.

Thalidomide, a racemate, is coming into clinical use as immuno-modulating and anti-inflammatory drug. Thalidomide was approved by the FDA in July 1998 for the treatment of erythema nodusum leprosum associated with leprosy. Recently, thalidomide is proving to be a promising drug in the treatment of a number of cancers and inflammatory diseases, such as multiple myeloma, inflammatory bowel disease (Crohn's disease), HIV and cancer associated cachexia. These effects may chiefly be exerted by S-thalidomide, but the enantiomers are inter-converted in vivo. Thalidomide is given orally, although parenteral administration would be desirable in some clinical situations. Thalidomide has been determined in formulations and, principally in biological fluids by a variety of methods such as high-performance liquid chromatography with ultraviolet detection and liquid chromatography coupled with tandem mass spectrometry. The overview includes the most relevant analytical methodologies used in its determination.

Measurement of uronic acids without interference from neutral sugars.

Replacement of carbazole with meta-hydroxydiphenyl greatly improves the determination of uronic acids in the presence of neutral sugars by preventing substantially, but not completely, the browning that occurs during the heating of sugars in concentrated sulfuric acid and avoiding the formation of additional interference by the carbazole reagent (Blumenkrantz, N., and Asboe-Hansen, G. (1973) Anal. Biochem. 54, 484-489). However, interference is still substantial when uronic acids are determined in the presence of excess neutral sugar, particularly because of the browning that occurs during the first heating before addition of the diphenyl reagent. The browning can be essentially eliminated by addition of sulfamate to the reaction mixture (Galambos, J. T. (1967) Anal. Biochem. 19, 119-132). Although others have reported that sulfamate and the diphenyl reagent were incompatible, we find that a small amount of sulfamate suppresses color production by a 20-fold excess of some neutral sugars without substantial sacrifice of the sensitive detection of uronic acids by the diphenyl reagent. Sodium tetraborate is required for the detection of D-mannuronic acid and enhances color production by D-glucuronic acid. We propose this modified sulfamate/m-hydroxydiphenyl assay as a rapid and reliable means for the assay of uronic acids, particularly when present in much smaller amounts than neutral sugars.