Solvent evaporation process

Fiber cross sections are also deterrnined by the coagulation conditions or, in the case of dry spinning, by the solvent evaporation process. The skin that forms early in the solvent removal process may remain intact as the interior of the filament deflates from solvent removal. Wet spun fibers from organic solvents are often bean shaped, while those from inorganic solvent systems are often round. Dry spun fibers, such as Du Font s Odon, are... 

Recently, an in-depth review on molecular imprinted membranes has been published by Piletsky et al. [4]. Four preparation strategies for MIP membranes can be distinguished (i) in-situ polymerization by bulk crosslinking (ii) preparation by dry phase inversion with a casting/solvent evaporation process [45-51] (iii) preparation by wet phase inversion with a casting/immersion precipitation [52-54] and (iv) surface imprinting. 

The steroid-loaded formulations are prepared by a patented solvent evaporation process (45,46). Basically, the wall-forming polymer and the steix>id are added to a volatile, water-immiscible solvent. The dispersion or solution is added to an aqueous solution to form an oil-in-water emulsion. The volatile solvent is then removed to afford solid microparticles. The microparticles are usually subd vided with sieves to isolate fractions of the desired diameters. It is i nper-ative that a reliable and reproducible microencapsulation procedure be used to fabricate long-acting formulations. 

Recently, Tsakala et al. (90) formulated pyrimethamine systems based on several lactide/glycolide polymers. These studies were conducted with both microspheres (solvent evaporation process) and implants (melt extrusion process). In vitro studies indicated that pyrimethamine-loaded implants exhibited apparent zero-order release kinetics in aqueous buffer whereas the microspheres showed an initial high burst and considerably more rapid drug release. In vivo studies in berghi infected mice confirmed that the microspheres did not have adequate duration of release for practical application. However, the implants offer promise for future clinical work as more than 3 months protection was observed in animals. 

F Koosha, RH Muller, SS Davis, MC Davies. The surface chemical structure of poly (/J-hydroxybutyrate) microparticles produced by solvent evaporation process. J Control Rel 9 149, 1989. 

Other semi-2-IPNs [52] processed by the freeze-drying method included IPN from 4,4 -bismaleimido diphenylmethane (BMI) and linear BTDA/3,4 -ODA polyamic acid that were dissolved in 1,3,5-trioxane (Fig. 16). The resulting semi-2-IPNs exhibited higher Tgs and reduced phase separation, and contained no plasticizing solvent. A comparison of unidirectional properties of composites prepared by the freeze-dry process to those by traditional solvent evaporation process is presented in Table 13. The freeze-drying method for the preparation of IPNs appears to be superior to previous technology. 

Compared with the solution absorption, the film sample prepared by spin-coating a dichlorobenzene solution using a slow solvent evaporation process showed pronounced peak broadening and a significant shift of —100 nm of the absorption edge. 

The preparation of biodegradable microspheres by a solvent evaporation process using sodium oleate as the emulsifier was described in previous publications (1.21. A number of process parameters (such as drug loading, polymer molecular weight, polymer composition and initial polymer solution concentration) were studied to determine their effects on the release of drugs from biodegradable microspheres. 

Cleland, J. L. (1998), Solvent evaporation processes for the production of controlled release biodegradable microsphere formulations for therapeutics and vaccines, Bio-technol. Prog., 14,102-107. 

Verrecchia,T., Huve, P., Bazile, D., Veillard, M., Spenlehauer, G., and Couvreur, P. (1993), Adsorption/desorption of human serum albumin at the surface of poly(lactic acid) nanoparticles prepared by a solvent evaporation process,/. Biomed. Mater. Res., 27(8), 1019-1028. 

Jaiswal J, Gupta SK, Kreuter J. Preparation of biodegradable cyclosporine nanoparticles by high-pressure emulsion-solvent evaporation process. / Control Release 2004 96(1) 169-178. 

LC-GC is usually limited to sample preconcentration and clean-up or to heart-cut analysis. Comprehensive LC-GC is difficult to accomplish because the solvent evaporation process is slow. Besides, the analytes contained in a single LC fraction can differ vastly with respect to their volatilities, which often requires the GC part of the separation to be carried out under temperature programmed conditions. Consequently, the time required for a single second dimension GC separation is measured in the best case in minutes rather than seconds, as in GC X GC. Thus, the... 

Thermodynamic incompatibility of the A and B block segments of amorphous AB and ABA block copolymers involves microphase separation at a critical micelle concentration (I, 2). The micelles formed at this concentration are essentially maintained through the solvent evaporation process to produce the domain structures observed in solid state (2, 3, 4). The shape and size of the micelles, and consequently of the domains, depend on the incompatibility, molecular weight, and fractional composition of the block copolymers and on the casting solvent and the temperature (3-10). 

In an early study by Lin et al., insulin-loaded polylactic acid (PLA) microcapsules were synthesized by an emulsification-solvent evaporation process originally reported by Beck et al. Several parameters in the synthesis process were modified with the intention of optimizing the insulin release profile. Such modifications included variations in types, concentrations, and viscosities of protective colloids used in the emulsification process. Polyvinyl alcohol (PVA), when used as the protective colloid in the fabrication process, was found to produce the PLA microparticles in reproducible quality. Further studies revealed that the concentration PVA directly affects the PLA particle size and the surface characteristics of the microcapsules. With higher concentrations of PVA, microparticles tended to be smaller and to have a smoother surface. When the release profiles of the microcapsules were stud-... 

Tice TR, Gilley RM. Preparation of injectable controlled release microcapsules by a solvent evaporation process. Journal of Controlled Release. 1985 2 343-352. 

Mateovic-Rojnik T, Frlan R, Bogataj M, Bukovec P, Mrhar A. Effect of preparation temperature in solvent evaporation process on Eudragit RS microsphere properties. Chemical and Pharmaceutical Bulletin. January 2005 53(1) 143-146. PubMed PMID 15635253. 

Chung TW, Huang YY, Tsai YL, Liu YZ. Effects of solvent evaporation rate on the properties of protein-loaded PLLA and POLL A microspheres fabricated by emnlsion-solvent evaporation process. Journal of Microencapsulation. July-August 2002 19(4) 463-471. PubMed PMID 12396383. 

From a microscopic standpoint, the molecules in the films are restricted in three-dimensional space between two walls having different characters one is the silicon wafer surface (hard wall) and the other is the air-polymer surface (soft wall). The polyimide films form the LOA during the solvent evaporation process. Moreover, aromatic polyimides possess intrinsically larger differences in the refi active indices along and perpendicular to the molecular chain directions than flexible coil macromolecules. On the other hand, the film thickness in this study are at least one to several orders of magnitude greater than the molecular size. The LOA may thus not... 

With these microdroplets, the solvent evaporation process will continue. Another Coulomb explosion may follow, leading to further reduction of the droplet size. The microdroplets play an important role in the analyte ionization. However, there are two theoretical models describing the actual ionization event, leading to gas-phase ions amenable to MS. In both models, the concept of preformed ions in solution plays an important role. 

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