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11.
《International Journal of Polymer Analysis and Characterization》2012,17(2):126-139
Abstract This work describes a method for analyzing polymer concentration in solution using density. The method can be applied to any polymer/solvent combination given certain experimental conditions; however, this study is specific to commercial samples of poly (n-butyl methacrylate) (PBMA) or poly (ethylene-co-vinyl acetate) (PEVA), two polymers of interest to Cordis Corporation. The test method was validated with respect to ICH requirements of linearity, accuracy, precision, range, etc.[ 1 , 2 ] The kinetic dissolution of PBMA or PEVA in tetrahydrofuran (THF) was evaluated as a practical analysis of Cordis process parameters. The results are provided as examples of the test method application. 相似文献
12.
《International Journal of Polymer Analysis and Characterization》2012,17(3):237-252
Abstract Chemically heterogeneous polymers can be separated according to composition by liquid chromatography. Usually, binary gradients are used where solvent strength and polarity are changed simultaneously. A new method employs three-component gradients: the starting eluent is a nonsolvent which ensures proper retention of the injected sample. A solvent of intermediate polarity is added next, the amount of which does not suffice for elution and is kept constant during the development of the chromatogram. The solvent is added in one step, polymer solubility is increased by a sudden transition to the desired solvent level. Finally, elution is triggered by the addition of a component which need not be a solvent but whose polarity fits the rules of liquid chromatography. Since there are many more nonsolvents than solvents for polymers, the new procedure offers a wider choice of suitable liquids. Further advantages are improved separation, independent control of solubility and adsorption, and suppression of unfavorable solvent effects. With copoly(styrene-stat-methyl methacrylate) separation according to composition was performed through acetonitrile, dichloromethane, and n-heptane in normal and reversed phase mode. The chromatographic results were compared with the solubility in the ternary system. 相似文献
13.
《International Journal of Polymer Analysis and Characterization》2012,17(1):61-84
Abstract In order to obtain absolute molecular weight information for hydroxypropyl methylcellulose HPMC from viscosity measurements, the physics of the viscosity-increasing effect of particles with extended shape on a flowing suspension has been elaborated. It is suggested that the phenomenon causes orientation of the particles producing complete alignment of the longer axis with the flow direction at sufficiently high shear rate, and that the viscosity increment per volume unit of particles, that is, the unitless laminar intrinsic viscosity [n]ø, approaches the relative axial ratio a of the particle as compared to the liquid constituents with increasing particle length if the particle is a sufficiently large object. Hence, provided that the required liquid dynamic conditions are fulfilled, corresponding to laminar Newtonian flow, viscosimetry can be used as an absolute method for determination of a. In the case of fully extended molecules, the weight-average molecular weight M w can then be estimated as M w = ([η 100ρ—1.5) Mual/au, where [η] is in dL/g, ρ (conversion factor into volume fraction) in g/mL, M u the molecular weight of the repeating unit (g/mol), au its axial ratio including solvation and a1 is the axial ratio of the liquid constituents. The theory is used to calculate M w of various commercial HPMC viscosity grades (3–10,000cP) of USP substitution type 2910 from capillary viscosimetry assuming complete extension as deduced from supplementing information obtained previously by osmometry. The value of ρ (g dry polymer/mL solvated polymer) is determined by å novel method based on the temperature influence on the specific viscosity jnder conditions of constant extension assuming that the solvation becomes negligible at a critical solution temperature T θ, coinciding with phase separation. Furthermore, the proposed model for the laminar dynamics of suspensions appears to be generally applicable to polymers; the constant K of the empirical relation [η] = KM α, usually referred to as the Mark—Houwink equation, is derived as K w = auM u −α/(a1100ρ), where K w is in dL g−1 (g/mol)−α. 相似文献
14.
Alexander R. Giaquinto Richard E. Lindstrom James Swarbrick Antonio LoSurdo 《Journal of solution chemistry》1977,6(10):687-701
Solubility and apparent molar volume data are used to demonstrate effects of amide alkylation on amide-water interactions at 25° C. Precise measurements were made of the apparent molar volumes of the amides in binary amide-water mixtures using a dilatometric technique. The results show that the apparent molar volumes of alkyl-substituted amides in water pass through a minimum at an amide concentration which varies inversely with the degree of alkylation. Further studies showed that the solubilities of methyl paraben (methyl-p-hydroxybenzoate) and naphthalene in various amide-water solvent systems increased in characteristic fashion with amide alkylation. 相似文献
15.
K. Mukae M. Sakurai S. Sawamura K. Makino S. W. Kim I. Ueda K. Shirahama 《Colloid and polymer science》1994,272(6):655-663
The swelling volume of poly(N-isopropylacrylamide) (PIPAAm) gel in aprotic solvents (acetonitrile (AcN)-, tetrahydrofuran (THF)-, 1,4-dioxane (DO)- and dimethylsulfoxide (DMSO))-water mixtures was measured at 25°C. The gel swollen in water shrank first and then reswelled with addition of the aprotic solvents. At an intermediate mole fraction (XDMSO) range of DMSO-water mixtures, the gel demonstrated a reentrant swelling phenomenon the hydrated gel shrank first on addition of a small amount of solvent, showed a typical wide reentrant transition, and gradually reswelled in the range near pure solvent. On the other hand, the gels in AcN-, THF-, and DO-water mixtures demonstrated a reentrant-convex swelling phenomenon: the gels reswelled after a reentrant phase transition in low Xorg (XAcN, XTHF and XDO), showed a maximum swelling in the intermediate Xorg region, and shrank again gradually in the high Xorg region. Such a swelling behavior of the gel was interpreted by correlating with solution properties of the aqueous aprotic solvent mixtures.The strength of hydrogen bonding around amide groups of the homopolymer was examined in pure solvents (water, THF, and DMSO) and in all proportion of aqueous THF to observe the relation with swelling behavior of gel by spectrum analysis of the amide I and II bands of Fourier Transform Infrared Spectroscopy (FT-IR). The swelling properties of gels in solvents and the aqueous mixtures were well correlated with the peak shifts of amide groups of the homopolymer. 相似文献
16.
H. Viernstein S. Reiter P. Wolschann 《Monatshefte für Chemie / Chemical Monthly》1994,125(6-7):681-689
Summary The solubility enhancement of triflumizole, a systemic fungicide, by -cyclodextrin inclusion complexation was investigated by electron absorption spectroscopy. The respective association constant determined by different methods was estimated to 470±20M
–1 in aqueous solution. A model for the host-guest complexation was deduced by molecular calculations.
Löslichkeitsverbesserung von Triflumizole durchHost-Guest-Complexierung mit -Cyclodextrin
Zusammenfassung Die Löslichkeitsverbesserung des systemischen Fungizids Triflumizole durch Komplexierung mit -Cyclodextrin wurde mittels Elektronenabsorptionsspektroskopie untersucht. Die entsprechende Stabilitätskonstante wurde durch verschiedene Methoden erfaßt und betrug im wäßrigen Medium 470±20M –1. Ein Model für denHost-Guest-Complex wurde durch Molekülrechnungen erstellt.相似文献
17.
Zoltán Aigner Ingrid Bencz Michael Kata 《Journal of inclusion phenomena and macrocyclic chemistry》1994,20(3):241-252
The incidence of genetic lipoprotein disorders, or hyperlipoproteinaemia, is currently increasing. Examinations were carried out on the hyperlipoproteinaemic drug fenofibrate and various cyclodextrin derivatives were applied to increase the solubility of this drug. Numerous products with several compositions (drug: CD mole ratio=2:1, 1:1, 1:2 or 1:3) were studied and three preparation methods (powder mixing, kneading and precipitation) were used. In vitro drug liberation and membrane diffusion examinations revealed compositions suitable for the preparation of a capsule dosage form (1:2 and 1:3 physical mixtures).Dedicated to Dr. Béla Selmeczi, university professor, with the best wishes for his 65th birthday. 相似文献
18.
19.
Solubility of carbon dioxide in aqueous solutions of sodium chloride: Experimental results and correlation 总被引：2，自引：0，他引：2
The solubility of carbon dioxide in aqueous solutions of sodium chloride was measured in the temperature range from 40 to 160°C, up to 6 mol-kg salt solutions and total pressures up to 10 MPa. Pitzer's(1) equations as well as the Chen and Evans(2) model were used to correlate the new data. Results are reported and compared to literature data and correlations. 相似文献
20.
Laura Sbrcea Ionu -Mihai T&#x;nase Adriana Lede i Denisa Cîrcioban Gabriela Vlase Paul Barvinschi Marinela Micl&#x;u Renata-Maria V&#x;ru&#x; Cristina Trandafirescu Ionu Lede i 《Molecules (Basel, Switzerland)》2020,25(23)
Risperidone (RSP) is an atypical antipsychotic drug which acts as a potent antagonist of serotonin-2 (5TH2) and dopamine-2 (D2) receptors in the brain; it is used to treat schizophrenia, behavioral and psychological symptoms of dementia and irritability associated with autism. It is a poorly water soluble benzoxazole derivative with high lipophilicity. Supramolecular adducts between drug substance and two methylated β-cyclodextrins, namely heptakis(2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) were obtained in order to enhance RSP solubility and improve its biopharmaceutical profile. The inclusion complexes were evaluated by means of thermoanalytical methods (TG—thermogravimetry/DTG—derivative thermogravimetry/HF—heat flow), powder X-ray diffractometry (PXRD), universal-attenuated total reflectance Fourier transform infrared (UATR-FTIR), UV spectroscopy and saturation solubility studies. Job’s method was employed for the determination of the stoichiometry of the inclusion complexes, which was found to be 2:1 for both guest–host systems. Molecular modeling studies were carried out for an in-depth characterization of the interaction between drug substance and cyclodextrins (CDs). The physicochemical properties of the supramolecular systems differ from those of RSP, demonstrating the inclusion complex formation between drug and CDs. The RSP solubility was enhanced as a result of drug encapsulation in the CDs cavity, the higher increase being obtained with DM-β-CD as host; the guest–host system RSP/DM-β-CD can thus be a starting point for further research in developing new formulations containing RSP, with enhanced bioavailability. 相似文献