Organic modifier evaporation

If the chromatographic eluent is a mixture of organic modifier and water and contains no additives such as involatile buffers/acids, then product recovery can be effected simply by removing solvent, e.g., by rotary evaporation. Alternatively, if the solvent volumes are large, the organic modifier can be removed by rotary evaporation and the product recovered by adsorption/elu-tion from a suitable adsorbent such as a reverse phase silica or an organic copolymer resin. This is also a method of choice where additives such as involatile buffers (phosphates, acetates) and acids (orthophosphoric) are present in the fraction and need to be removed. 

Organic method The same Si02 support was used. The organic modified support was prepared starting from Ti[OCH(CH3)2]4 (Aldrich, 99+%) in isopropanol (Aldrich, 99+%), following the same procedure as described above, but in this case the solvent was evaporated at 70"C. The sample is denoted as Ti-SiOj/O. 

Mobile-Phase Composition Slow changes in mobile-phase composition are also a common cause of retention-time drifts. The most common cause is the evaporation of a mobile-phase constituent In reversed-phase chromatography, the organic modifier is more volatile than water, and an increase in retention will occur over time. The evaporation of a part of the mobile phase can be amplified by sparging with helium, which is commonly used to remove air from the mobile phase. 

In intercalation of polymer from solution mode of nanocomposite synthesis, the organically modified silicate is dispersed in a solvent in which the polymer is also soluble. The polymer then adsorbs onto the delaminated sheets followed by the evaporation of the solvent. When the solvent is evaporated, the sheets reassemble, which also trap the polymer chains in between. Thus, an ordered multilayer structure is usually formed using this approach. The polymer chains loose entropy in the process of intercalation, which is compensated by the increase in the entropy of the solvent molecules due to their desorption from the filler interlayers. The technique is mostly used for the intercalation of the water-soluble polymers Uke poly(vinyl alcohol), poly(ethylene oxide), poly(acrylic acid), poly(vinlypyrroUdone), etc. [20-24], Later on, the use of this technique was also undertaken in organic solvents for polymers nonsoluble in water [25, 26],... 

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