Solvent evaporation technique

An on-line supercritical fluid chromatography-capillary gas chromatography (SFC-GC) technique has been demonstrated for the direct transfer of SFC fractions from a packed column SFC system to a GC system. This technique has been applied in the analysis of industrial samples such as aviation fuel (24). This type of coupled technique is sometimes more advantageous than the traditional LC-GC coupled technique since SFC is compatible with GC, because most supercritical fluids decompress into gases at GC conditions and are not detected by flame-ionization detection. The use of solvent evaporation techniques are not necessary. SFC, in the same way as LC, can be used to preseparate a sample into classes of compounds where the individual components can then be analyzed and quantified by GC. The supercritical fluid sample effluent is decompressed through a restrictor directly into a capillary GC injection port. In addition, this technique allows selective or multi-step heart-cutting of various sample peaks as they elute from the supercritical fluid... 

The solvent evaporation technique is based on the use of organic solvents as dissolving agents for the lipid matrix (i.e., phospholipids or triglycerides and monoglycerides) and the subsequent evaporation of the solvent within an aqueous medium until a CLS dispersion is obtained. 

Fig. 3 Preparation of polymeric nanoparticles by emulsion solvent evaporation technique...

O Donnell PB, McGinity JW (1997) Preparation of microspheres by the solvent evaporation technique. Adv Drug Deliv Rev 28 25-42... 

The slow solvent evaporation technique afforded milky nanosphere dispersions. No effect of the polymer/protein/lipid weight ratios on the dispersion stability was detected, at least in the investigated range. 

By taking into account the difficulties connected to the slow solvent evaporation technique, a new procedure for nanoparticle preparation by co-precipitation was set up. This technique does not use chlorinated solvents and energetic mixing, which are both known to cause appreciable protein denaturation[17,18]. 

The encapsulation of bioactive agents, such as proteins or peptides, presents a special problem due to the delicacy of their structural conformation. Their biological activity may be irreversibly disturbed even by small changes of pH, temperature, or ionic concentration [192,200]. Spray-drying and double emulsion solvent evaporation techniques (w/o/w) have been suggested for the incorporation of proteins with retention of their bioactivity [99,192,202,198]. 

Samples for the viscoelastic experiments were prepared by a conventional slow-solvent-evaporation technique (1) followed by vacuum drying. For ease in handling in certain experiments, some samples were lightly cured using a 30-MRad dose of electrons other experiments were carried out on uncured materials. Transmission electron microscopy (Phillips Model 200) was used to investigate possible morphological features in the block polymers and blends. Details of the various staining techniques used are presented elsewhere (1,11,12,13). 

Ramesh, V. D., Medlicott, N., Razzak, M., and Tucker, I. G. (2002), Microencapsulation of FITC-BSA into poly(e-caprolactone) by a water-in-oil-in-oil solvent evaporation technique. Trends Biomater. Artif. Organs, 15, 31-36. 

Emulsion Solvent Evaporation The basic concept of the emulsion solvent evaporation technique producing nanoparticles is very straightforward. The particles are formed as an emulsion of a polymer-surfactant mixture and dispersed in an organic solvent. The solvent is then evaporated to leave behind the individual emulsion droplets which form stable free nanoparticles [203], This method is far easier and more preferable over methods such as spray drying and homogenization and operates under ambient conditions and mild emulsification conditions. The size and composition of the final particles are affected by variables such as phase ratio of the emulsion system, organic solvent composition, emulsion concentration, apparatus used, and properties of the polymer [204],... 

High-molecular-weight PM PS is soluble in common solvents and is a good film former. Qualitatively, the overall handling characteristics resemble those of polystyrene. Films of PM PS were cast from toluene solution by a solvent evaporation technique. Other polysilylenes, poly(methylcyclohexylsilylene), poly(methyl-n-pro-pylsilylene), poly(methyl-n-octylsilylene), and a copolymer of dimethyl- and meth-ylphenylsilylene (1 1 ratio) were also prepared by Wurtz coupling by the method of Zhang and West (47). Films of these polymers were also cast from toluene. All polymers form clear transparent colorless films. 

Iwata M, McGinity JW. Preparation of multi-phase microspheres of poly(D,L-lactic acid) and poly(D,L-lactic co-glycolic acid) containing a w/o emulsion by a multiple emulsion solvent evaporation technique. / Microencapsul 1992 9(2) 201-214. 

Columns for LLPC are prepared by using solvent evaporation, direct coating, precipitation, or a dynamic coating technique [3], In the solvent-evaporation technique, the nonvolatile hquid stationary phase is dissolved in a volatile solvent and mixed with the dry sup-... 

The freeze-drying method is one of solvent volatilization, but it differs from the common solvent evaporation techniques in that the solvent is sublimed from the solid state. A solution, prepared by means of soluble salts or by dissolving metals in acid, is frozen and the solid solvent, usually water in the form of ice, is sublimed away giving the dried salts. The process gives high surface area powders of excellent chemical homogeneity. 

Low volatility at the highest applied temperature (except when the solvent evaporation technique is used). 

Figure 2. Schematic representation of metal nanoparticles film fabrication by casting and solvent evaporation technique.

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