Search results for "Solubility"
showing 10 items of 681 documents
Design of nonionic surfactants for supercritical carbon dioxide
1996
Interfacially active block copolymer amphiphiles have been synthesized and their self-assembly into micelles in supercritical carbon dioxide (CO 2 ) has been demonstrated with small-angle neutron scattering (SANS). These materials establish the design criteria for molecularly engineered surfactants that can stabilize and disperse otherwise insoluble matter into a CO 2 continuous phase. Polystyrene- b -poly(1,1-dihydroperfluorooctyl acrylate) copolymers self-assembled into polydisperse core-shell-type micelles as a result of the disparate solubility characteristics of the different block segments in CO 2 . These nonionic surfactants for CO 2 were shown by SANS to be capable of emulsifying u…
Trehalose-hydroxyethylcellulose microspheres containing vancomycin for topical drug delivery.
2001
Abstract A new formulation, in which vancomycin is entrapped into trehalose and hydroxyethylcellulose (Natrosol ® ) spherical matrices, is described. Microspheres were produced by the solvent evaporation method. The entrapped drug was fully recovered following microspheres dissolution. Differential scanning calorimetry analyses proved that Natrosol maintains trehalose in its amorphous form. The stabilizing effects of trehalose on vancomycin were evaluated even after long storage and heating of microspheres. Calorimetric data indicated no decomposition of the entrapped drug. In vitro drug release, already performed by using a general two-compartment linear time-invariant open model, suggests…
The impact of the EMA change in definition of "dose" on the BCS dose-solubility ratio: a review of the biowaiver monographs.
2013
The Biopharmaceutics Classification System (BCS) defines the solubility characteristics of an active pharmaceutical substance based on its dose-solubility ratio: for highly soluble drugs this ratio is less than 250 mL over a defined pH range. Prior to the revision of the European Medicines Agency (EMA, formerly EMEA) guideline in 2010, the "dose" in this ratio was consistently defined by the US FDA, the EMA, and the WHO biowaiver guidelines as the highest dosage strength. However, in the revised EMA guideline, the dose is defined as the highest single dose administered according to the Summary of Product Characteristics. The new EMA criterion for highly soluble may be closer to the actual c…
Aqueous coefficient calculations for chemicals and drugs
1999
Aqueous functional group activity coefficients (AQUAFAC) is a group‐contribution method for estimating the aqueous coefficients. We have written a program for the calculation of these coefficients. The solubility S w of alkanes shows variation of 8 orders of magnitude. The comparison with experiment shows that AQUAFAC gives good S w estimations. For 4'‐substituted acetanilides, I‐, Br‐, nitro‐, Cl‐, F‐ and methoxy‐substituents decrease S w, while formyl‐ and amino‐substituents increase S w. For acetaminophen esters, S w decreases from the acetate to the decanoate. The S w of 29 barbiturates shows typical errors of 0.4 log S w units. For the cyclo‐alkane‐l’,5‐spirobarbituric acids, S w decre…
Polycarboxylic acids in sea water: acid–base properties, solubilities, activity coefficients, and complex formation constants at different salinities
2016
This paper reports the results of the investigations carried out in synthetic sea water at different salinities for different classes of polycarboxylic acids. The investigations can be summarized as follows: (a) Determination of the protonation constants in such multicomponent solution in a salinity range 15 ≤ S ≤ 45, at t = 25 °C, for the linear dicarboxylic acids HOOC-(CH2) n –COOH (0 ≤ n ≤ 8), and aromatic polycarboxylic acids (o-phthalic and 1,2,4-benzenetricarboxylic acids). For malonic, succinic, 1,2,3-benzenetricarboxylic, and 1,2,3,4-benzenetetracarboxylic acids, investigations were also carried out at t = 10 and 37 °C; (b) Determination of the total and intrinsic solubility (S T an…
Potential of phosphonium-based ionic liquids to purify 1-propanol from water by liquid–liquid extraction at mild conditions
2022
Abstract In order to reduce the environmental of the separation of 1-propanol from water in a residual industry stream for its reuse, the capability as solvents of two different trihexyl(tetradecyl)phosphonium ionic liquids (ILs) – trihexyl(tetradecyl)phosphonium chloride ([TDTHP][Cl]) and trihexyl(tetradecyl)phosphonium bromide ([TDTHP][Br])-, was studied. The liquid–liquid equilibria data for both ternary systems, {water + 1-propanol + [TDTHP][Cl]} and {water + 1-propanol + [TDTHP][Br]} at different mild work temperatures, (283.2, 303.2 and 323.2) K, and atmospheric pressure were measured. The thermodynamic parameters for both ternary systems at different work conditions were obtained by …
Modeling S-carboxymethyl-L-cysteine protonation and activity coefficients in sodium and tetramethylammonium chloride aqueous solutions by SIT and Pit…
2007
Solubility and acid–base properties of S-carboxymethyl-l-cysteine (carbocysteine, ccys) in NaClaq and tetramethylammonium chloride, (CH3)4NClaq ,a tt =2 5 ◦ C and at different ionic strengths were investigated. Solubility was studied at 1.0 ≤ I (mol L −1 ) ≤ 5.0 for NaClaq and 1.0 ≤ I (mol L −1 ) ≤ 3.0 for (CH3)4NClaq, while potentiometric measurements (by ISE-H + , glass electrode) were performed at 0.1 ≤ I (mol L −1 ) ≤ 5.0 for NaClaq and 0.5 ≤ I (mol L −1 ) ≤ 3.0 for (CH3)4NClaq. Solubility data allowed us to determine Setschenow constants and activity coefficients of neutral carbocysteine (H2ccys). Dependence on ionic strength and ionic medium of protonation constants and activity coeff…
Solubility and acid-base properties and activity coefficients of chitosan in different ionic media and at different ionic strengths, at T=25°C
2009
Studies on the acid-base properties and solubility of a polyammonium polyelectrolyte (chitosan) with different molecular weights (MW 310 and 50 kDa), were performed at T=25 °C, in the pH range 2.5–7. The protonation of chitosan was investigated by potentiometry ([H+]-glass electrode) in NaCl, NaNO3 and mixed NaNO3+Na2SO4 ionic media, at different ionic strengths. Protonation constants were calculated as a function of dissociation degree α by means of two different models, namely, a simple linear model and the modified Henderson–Hasselbalch equation. Experimental data were also fitted using a model independent of α (Diprotic-like model), according to which the acid-base properties can be sim…
Calculations of organic-solvent dispersions of single-wall carbon nanotubes
2005
The aqueous solubility Sw and 1-octanol–(Po), cyclohexane–(Pch), and chloroform–(Pcf) water partition coefficients are calculated. The properties of single-wall carbon nanotubes (SWNT) are related to the indices (n, m) designating the chiral vector. SWNTs are classified in zigzag (n, 0), armchair (n, n), and chiral (n, m). These properties permit classifying SWNTs according to (n, m). Correlations between (n2 + nm + m2)1/2, log Sw, log Po, log Pch, and log Pcf show that (n, m) are adequate indices. The (10,10) is the most abundant SWNT, presenting consistency between great kinetic stability, small Sw, and great {Po, Pch, Pcf}. The room temperature solubility of SWNTs is investigated in a va…
Coexpression of IL-6 and soluble IL-6R causes nodular regenerative hyperplasia and adenomas of the liver
1998
Studies with tumor necrosis factor p55 receptor- and interleukin-6 (IL-6)-deficient mice have shown that IL-6 is required for hepatocyte proliferation and reconstitution of the liver mass after partial hepatectomy. The biological activities of IL-6 are potentiated when this cytokine binds soluble forms of its specific receptor subunit (sIL-6R) and the resulting complex interacts with the transmembrane signaling chain gp130. We show here that double transgenic mice expressing high levels of both human IL-6 and sIL-6R under the control of liver-specific promoters spontaneously develop nodules of hepatocellular hyperplasia around periportal spaces and present signs of sustained hepatocyte prol…