High-Molecular Components Separation

High molecular components may be found in the effluent of some reactors, as for cracking, oxidation, etc. Because there is a danger of fouling downstream units, these heavies should be removed before other separators. Fig. 7.22 presents some solutions. An adsorption device, as for example a clay tower, could solve partially the problem. 

Ultrafiltration is used over a wide field of applications involving situations where high molecular components have to be separated from low molecular components. Applications... 

The presence of proteins, polymers and other substances with high molecular weights sometimes affects the polarographic waves of the substance to be analysed. These effects are often caused by the formation of an adsorbed layer at the dropping mercury electrode. Thus it is sometimes preferable to separate first the high-molecular components before the solution is polarographed. 

A major problem whidi has to be fac in all repetitive-type syntheses where excess reagents are used is the purification of the polymer or the removal of low-molecular compounds. Be e prediction of the sui rt, lich apfdied even in the beginning of the use of soluble polymers before being refined later by the introduction of crystalline polymers, in many studies on liquid-phase application, membrane filtration was also used for the separation of low- and high-molecular components in solution [10, 25-28,42-48]. The experimental arrangement of a typncal membrane filtration system is depicted in Fig. 1. 

For mixture.s the picture is different. Unless the mixture is to be examined by MS/MS methods, usually it will be necessary to separate it into its individual components. This separation is most often done by gas or liquid chromatography. In the latter, small quantities of emerging mixture components dissolved in elution solvent would be laborious to deal with if each component had to be first isolated by evaporation of solvent before its introduction into the mass spectrometer. In such circumstances, the direct introduction, removal of solvent, and ionization provided by electrospray is a boon and puts LC/MS on a level with GC/MS for mixture analysis. Further, GC is normally concerned with volatile, relatively low-molecular-weight compounds and is of little or no use for the many polar, water soluble, high-molecular-mass substances such as the peptides, proteins, carbohydrates, nucleotides, and similar substances found in biological systems. LC/MS with an electrospray interface is frequently used in biochemical research and medical analysis. 

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