Archive ouverte UNIGE | last documents for author 'Jérôme Barra'https://archive-ouverte.unige.ch/Latest objects deposited in the Archive ouverte UNIGE for author 'Jérôme Barra'engEffect of particle size on the interaction of powders in binary mixes, correlation with surface energy and cohesion parametershttps://archive-ouverte.unige.ch/unige:86447https://archive-ouverte.unige.ch/unige:86447abstract not availableMon, 29 Aug 2016 12:56:59 +0200Partial solubility parameters of piroxicam and niflumic acidhttps://archive-ouverte.unige.ch/unige:85267https://archive-ouverte.unige.ch/unige:85267The expanded Hansen method is tested with two anti-inflammatory drugs, piroxicam (preferentially Lewis base) and niflumic acid (preferentially Lewis acid). The original dependent variable, ln α2/U, where α is the activity coefficient and U is related to the molar volume of the solute and the volume fraction of the solvent, was compared with the direct use of the logarithm of the mole fraction solubility ln X2 in the three- and four parameter models. The activity coefficient of the drugs was calculated from the heat and temperature of fusion before and after equilibration of each solid phase with the pure solvents used. The dependent variables ln X2 and ln α2/U provided similar partial solubility parameter values for piroxicam with the four parameter model. All the partial parameters of niflumic acid were significant statistically only with the variable ln X2. This indicates that ln X2 is the most suitable variable for the determination of partial solubility parameters. The dispersion solubility parameters are similar for both drugs, the largest differences being observed for the dipolar and hydrogen bonding parameters. The partial solubility parameters give insights into the interaction capability of the drugs and are consistent with their chemical structure. For niflumic acid, a better proton donor, δa>δb whereas for piroxicam, a preferentially Lewis base δb>δa. This result is particularly interesting as it demonstrates for the first time the validity of the method for a mainly proton-acceptor compound.Thu, 14 Jul 2016 09:06:21 +0200Proposition of group molar constants for sodium to calculate the partial solubility parameters of sodium salts using the van Krevelen group contribution methodhttps://archive-ouverte.unige.ch/unige:84816https://archive-ouverte.unige.ch/unige:84816The aim of this study is to propose, for the first time, a set of group molar constants for sodium to calculate the partial solubility parameters of sodium salts. The values were estimated using the few experimental partial solubility parameters of acid/sodium salt series available either from the literature (benzoic acid/Na, ibuprofen acid/Na, diclofenac Na) or determined in this work (salicylic acid/Na, p-aminobenzoic acid/Na, diclofenac), the group contribution method of van Krevelen to calculate the partial parameters of the acids, and three reasonable hypothesis. The experimental method used is a modification of the extended Hansen approach based on a regression analysis of the solubility mole fraction of the drug lnX(2) against models including three- or four-partial solubility parameters of a series of pure solvents ranging from non-polar (heptane) to highly polar (water). The modified method combined with the four-parameter model provided the best results for both acids and sodium derivatives. The replacement of the acidic proton by sodium increased the dipolar and basic partial solubility parameters, whereas the dispersion parameter remained unaltered, thus increasing the overall total solubility parameter of the salt. The proposed group molar constants of sodium are consistent with the experimental results as sodium has a relatively low London dispersion molar constant (identical to that of -OH), a very high Keesom dipolar molar constant (identical to that of -NO(2), two times larger than that of -OH), and a very high hydrogen bonding molar constant (identical to that of -OH). The proposed values are: F((Na)d)=270 (J cm(3))(1/2) mol(-1); F((Na)p)=1030 (J cm(3))(1/2) mol(-1); U((Na)h)=17000 J mol(-1). Like the constants for the other groups, the group molar constants proposed for sodium are certainly not the exact values. However, they are believed to be a fair approximation of the impact of sodium on the partial solubility parameters and, therefore, can be used as such in the group contribution method of van Krevelen.Tue, 28 Jun 2016 15:56:14 +0200Influence of the Physicochemical Variability of Magnesium Stearate on Its Lubricant Properties: Possible Solutionshttps://archive-ouverte.unige.ch/unige:83152https://archive-ouverte.unige.ch/unige:83152The variability of the physicochemical properties of 13 commercial batches of magnesium stearate (from three vendors) were determined using various physicochemical tests. Differences observed were related to the crystal lattice and the hydration state of the samples as well as the impurities contained in their matrices. A formulation model containing 2% of magnesium stearate was used to determine the lubricant properties of 6 of the 13 magnesium stearate lots received. The tablet press used was a Stoks® Single Station Instrumented F Press. The different lubricant properties observed were related to the particle size of the magnesium stearate lot used. The influence of the crystalline structure on the lubricant properties of magnesium stearate was also shown whereas the influence of the adsorbed water did not appear to determine process capabilities. Two possible solutions were evaluated to reduce the lubricant property differences among the lots tested. By decreasing the particle size of a lot of magnesium stearate, it has been possible to significantly improve its lubricant properties. Magnesium stearate in association with talc also presented an improvement of its lubricant properties.Mon, 18 Apr 2016 14:01:11 +0200Partial solubility parameters of lactose, mannitol and saccharose using the modified extended Hansen method and evaporation light scattering detectionhttps://archive-ouverte.unige.ch/unige:77705https://archive-ouverte.unige.ch/unige:77705The modified extended Hansen method was tested for the first time to determine partial solubility parameters of non-polymeric pharmaceutical excipients. The method was formerly tested with drug molecules, and is based upon a regression analysis of the logarithm of the mole fraction solubility of the solute against the partial solubility parameters of a series of solvents of different chemical classes. Two monosaccharides and one disaccharide (lactose monohydrate, saccharose and mannitol) were chosen. The solubility of these compounds was determined in a series of solvents ranging from nonpolar to polar and covering a wide range of the solubility parameter scale. Sugars do not absorb at the UV-vis region, and the saturated solutions were assayed with a recent chromatographic technique coupled to an evaporative light scattering detector. This technique was suitable to determine the concentration dissolved in most solvents. The modified extended Hansen method provided better results than the original approach. The best model was the four parameter equation, which includes the dispersion delta d, dipolar delta p, acidic delta a and basic delta b partial solubility parameters. The partial solubility parameters obtained, expressed as MPa1/2, were delta d = 17.6, delta p = 28.7, delta h = 19, delta a = 14.5, delta b = 12.4, delta T = 32.8 for lactose, delta d = 16.2, delta p = 24.5, delta h = 14.6, delta a = 8.7, delta b = 12.2, delta T = 32.8 for mannitol and delta d = 17.1, delta p = 18.5, delta h = 13, delta a = 11.3, delta b = 7.6, delta T = 28.4 for saccharose. The high total solubility parameters delta T obtained agree with the polar nature of the sugars. The dispersion parameters delta d are quite similar for the three sugars indicating that the polar delta p and hydrogen bonding parameters (delta h, delta a, delta b) are responsible for the variation in the total solubility parameters delta T obtained, as also found for drugs. The results suggest that the method could be extended to determine the partial solubility parameters of other non-polymeric pharmaceutical excipients.Wed, 25 Nov 2015 13:51:32 +0100