objective(s) the aim of this study was to formulate and evaluate microencapsulated controlled release preparations of theophylline using ethylcellulose as the retardant material with high entrapment efficiency. materials and methods microspheres were prepared by water-in-oil-in-oil (w/o1/o2) emulsion-solvent diffusion (esd). a mixed solvent system consisting of acetonitrile and dichloromethane ...

a multiple-unit oral floating system was prepared using the emulsification-solvent diffusion method to prolong the gastric emptying time of theophylline. for this purpose, theophylline, ethyl cellulose and dibutyl phthalate were dissolved in an ethanol/dichloromethane mixture, added to 0.1 m hcl containing nacl (20%) or saturated theophylline and/or different concentrations of polysorbate 80 an...

objective(s) ibuprofen is a problematic drug in tableting, and dissolution due to its poor solubility, hydrophobicity, and tendency to stick to surface. because of the bad compaction behavior ibuprofen has to be granulated usually before tableting. however, it would be more satisfactory to obtain directly during the crystallization step crystalline particles that can be directly compressed and ...

While the Stokes-Einstein (SE) equation predicts that the diffusion coefficient of a solute will be inversely proportional to the viscosity of the solvent, this relation is commonly known to fail for solutes, which are the same size or smaller than the solvent. Multiple researchers have reported that for small solutes, the diffusion coefficient is inversely proportional to the viscosity to a fr...

Magnetic resonance imaging is used to study changing microstructure and molecular motion during dissolution of poly(vinyl alcohol) (PVA) in water. One-dimensional water concentration profiles were measured as a function of distance from the polymer-solvent interface. Diffusion-weighted profiles were used to calculate the spatial variation of the self-diffusion coefficient of water. The results ...

The diffusion behavior of methanol in different critical media (n-pentane, n-hexane, n-heptane and acetone) was investigated by the Monte Carlo (MC) method. From the simulation results, the diffusion constant of methanol molecule in the critical n-hexane is much larger than those in n-pentane, n-heptane and acetone. By analyzing the microscopic configurations of the critical mixtures, it is fou...

objective(s):the aim of this study was to improve flowability and compressibility characteristics of starch to use as a suitable excipient in direct compression tabletting. quasi-emulsion solvent diffusion was used as a crystal modification method. materials and methods: corn starch was dissolved in hydrochloric acid at 80˚c and then ethanol as a non-solvent was added with lowering temperature ...

A semi-empirical study into the effects of residual casting solvent on the lithographic properties of photoresist is described. Solvent content of a commercial i-line photoresist after post apply bake has been measured using a quartz crystal microbalance and using radio-labeled solvent with scintillation counting. Analysis of this data has led to a calibrated model of solvent diffusivity as a f...