The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Jyri Pekka Mikkola - One of the best experts on this subject based on the ideXlab platform.
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dissolution of lignocellulosic materials and its constituents using ionic liquids a review
Industrial Crops and Products, 2010Co-Authors: Paivi Makiarvela, Ikenna Anugwom, Pasi Virtanen, Rainer Sjoholm, Jyri Pekka MikkolaAbstract:The state of art from the dissolution of cellulose, lignin and wood using ionic liquids is presented in this work. The emphasis is put on the relationship between the properties of ionic liquids and the dissolution capacity. The impact of the following solvation Parameters, namely Hildebrand Solubility Parameter and hydrogen bond basicity are related to the dissolution of lignocellulosic material. Good solvents for cellulose are 1-butyl- and 1-allyl-3-methylimidazolium chlorides as well as 1-ethyl-3-methylimidazolium acetate, whereas for lignocellulosic material the best solvents are 1-ethyl-3-methylimidazolium acetate and 1-allyl-3-methylimidazolium chloride. In allyl group the ethylene functionality facilitates B-interactions with the aromatic lignin structure. Furthermore, small polarizable anions are also powerful when aiming at dissolution of cellulose. The properties of regenerated cellulose and reconstituted lignin are also given and compared with those of the native materials. Furthermore, the results from the regeneration and reuse of ionic liquids are presented here.
Begoña Escalera - One of the best experts on this subject based on the ideXlab platform.
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Hildebrand Solubility Parameter to predict drug release from hydroxypropyl methylcellulose gels
International Journal of Pharmaceutics, 2011Co-Authors: Pilar Bustamante, J Navarrolupion, M A Pena, Begoña EscaleraAbstract:Abstract An equation including the Hildebrand Solubility Parameter δ of the drugs is used for the first time to model drug release from hydroxypropyl methylcellulose (HPMC) gels: ln M = −21.578 + 2.102 δ − 0.037 δ 2 + 0.48 ln t + 1.028 ln C i ( r 2 = 0.94 for a total of 286 cases). The experimentally determined release data of six drugs having different polarity (caffeine, theophylline, paracetamol, salicylic acid, naproxen and diclofenac) at several initial concentrations C i were included in the equation. In general, the amount of drug delivered is linear at the first 5–6 h of the release profiles and the zero order constants K o increase as the Solubility Parameter of the drugs become larger. The Peppas exponential law M / M ∞ = Kt n is applicable to larger fractional release, until 67–87% (48–51 h) for the less polar drugs (diclofenac and naproxen, lower δ values) and more than 80% (26–28 h) for the more polar drugs (higher δ values, theophylline, salicylic acid, caffeine and paracetamol). The Peppas release rate (ln K ) shows a parabolic relationship with the drug Solubility Parameter. The diffusional exponent n varies between 0.40 and 0.58 indicating that drug release is mainly controlled by diffusion. An extended form of the Peppas equation is also tested for each drug including all the initial concentrations: ln M = a + b ln t + c ln C i ( r 2 = 0.88–0.94). The logarithm of the octanol–water partition coefficients can also be used in combination with the drug concentrations.
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Relationship between swelling of hydroxypropylmethylcellulose and the Hansen and Karger partial Solubility Parameters
Journal of Pharmaceutical Sciences, 2005Co-Authors: Francisco Javier Navarro-Lupión, Pilar Bustamante, Begoña EscaleraAbstract:A model that relates the equilibrium swelling of hydroxypropylmethylcellulose to the partial Solubility Parameters of both the polymer and the solvents is proposed to interpret and correlate the experimental data. The non-specific interactions are expressed as the dispersion delta(d) and polar delta(p) Solubility Parameters of Hansen, or as a combination of both. Hydrogen bonding is represented by the acidic delta(a) and the basic delta(b) Karger Solubility Parameters. The results are compared with models including the same Parameters for non-specific interactions (delta(d) and delta(p)) and the Hansen hydrogen bonding Parameter delta(h). Equilibrium swelling of this hydrophilic polymer that is widely used in drug formulation is measured in pure solvents covering a wide polarity range. In a qualitative way, swelling increases in solvents with higher Hildebrand Solubility Parameters and stronger hydrogen bonding capability, and it decreases in non-polar solvents. Single polarity indexes, such as the Hildebrand Solubility Parameter or the partition coefficient (PC), do not fit well the overall experimental data. The best correlations were obtained with the proposed model, providing at the same time an interpretation consistent with the physical meaning of the terms included in the equation. Swelling increases as the non-specific interactions of the polymer and the solvents become alike, and as the Lewis acid-base interactions of the polymer (1) and the solvent (2) represented by the products delta(1a)delta(2b) and delta(1b)delta(2a) become greater. Conversely, hydrogen bonding self association of the solvents (the product delta(1a)delta(1b)) lowers swelling. The results show that the Karger hydrogen bonding Parameters provide a better approach than the Hansen hydrogen bonding Parameter to correlate the swelling behavior of a hydrophilic polymer.
W H M Oostrom - One of the best experts on this subject based on the ideXlab platform.
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enzymic transesterification in near critical carbon dioxide effect of pressure Hildebrand Solubility Parameter and water content
Enzyme and Microbial Technology, 1992Co-Authors: M H Vermue, J Tramper, J P J De Jong, W H M OostromAbstract:Abstract The transesterification of nonanol and ethyl acetate into nonyl acetate and ethanol by Mucor miehei lipase was studied in near-critical carbon dioxide. Before studying the enzymic reaction, the homogeneity of the reaction medium was evaluated to make sure that the reaction was executed in homogeneous near-critical carbon dioxide. Estimations of the solubilities of the substrates were made using the difference in Hildebrand Solubility Parameter between the carbon dioxide and both substrates. A difference smaller than 10(MPa)0.5, which is needed for solubilization of apolar compounds in supercritical fluids as found by Allada et al., also holds for the compounds in our reaction system. The effects of pressure, polarity, and water content of the medium on the enzymic reaction have been studied in a continuous stirred-tank reactor. The pressure and polarity of the near-critical carbon dioxide as expressed by the Hildebrand Solubility Parameter hardly influenced the transesterification rate of the lipase. By increasing the water content in the system from 0.05 to 0.2% (itv/v), the product formation decreased. The transesterification rate in near-critical carbon dioxide proved to be much lower than in hexane at comparable conditions of temperature, water content, and substrate and enzyme concentration.
P B Rathi - One of the best experts on this subject based on the ideXlab platform.
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Solubility prediction of satranidazole in methanol water mixtures using extended Hildebrand Solubility Parameter approach
Asian Journal of Research in Chemistry, 2011Co-Authors: P B RathiAbstract:Models for predicting Solubility of drugs in solvent mixtures have an important practical application in drug formulation. Solvent mixtures are widely used in pharmacy, and theoretical and semiempirical approaches save experiments that are often expensive and time-consuming. The study of Solubility behaviour of satranidazole in solvent blends and individual solvents ranging from non-polar to highly polar is essential. The total Solubility Parameter explains the interactions of the drug between solute and solvent. The solutions containing excess drug were shaken in a water bath for 72 h at 25°C. The solutions attained equilibrium were then filtered and analyzed for drug content. The Extended Hildebrand Solubility Approach was used to process the Solubility data of satranidazole. For understanding the solute-solvent interactions, total Solubility Parameter concept was utilized. A multiple regression method using the Extended Hildebrand Solubility Parameter Approach was applied to verify the Solubility's of satranidazole in pure polar solvents. Fedors group contribution method was used to calculate the Solubility Parameter of satranidazole and to support the results obtained from Extended Hildebrand Theory. The method has potential usefulness in preformulation and formulation studies during which Solubility prediction is important for drug design.
Jalil Moghadasi - One of the best experts on this subject based on the ideXlab platform.
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further property of ionic liquids Hildebrand Solubility Parameter from new molecular thermodynamic model
Journal of Molecular Liquids, 2016Co-Authors: Mohammad Mehdi Alavianmehr, Sayed Mostafa Hosseini, A A Mohsenipour, Jalil MoghadasiAbstract:Abstract A molecular thermodynamic-based approach has been previously employed to correlate the surface tension of ionic liquids (ILs). This paper aims to calculate further property of ILs, the Solubility Parameter of 27 ILs having imidazolium, pyrrolidinium, pyridinium, phosphonium, piperidinium and ammonium cations by the help of that approach along with an ion contribution-based equation of state (EOS). The proposed model calculates the internal pressure of ILs using a statistical mechanical expression and subsequently their Solubility Parameters through a simple relation. In this respect, contributions to internal pressure from the hard-sphere repulsion, Lennard-Jones dispersion force, and columbic interactions are considered and assumed to be additive in the development of the model. The performance of the proposed model is checked against the literature Solubility Parameters of ILs over temperature range within 298–358 K. The proposed model has a sound basis of statistical-mechanics which incorporates contributions arising from the hard-sphere repulsion, Lennard-Jones dispersion forces. Further, the electrostatic interaction is taken into account using the mean spherical approximation (MSA). The outcomes of our model are also compared with those obtained based on the vaporization enthalpies and molar volumes, for which their values are available in literature. Generally, the new molecular model represents accurately the Solubility Parameters of studied ILs with uncertainty of the order of ± 2.33%. The miscibility of some non-polar and polar hydrocarbons in ILs is also investigated by the use of their Solubility Parameters and Flory–Huggins interaction Parameter.