Size exclusion retention

In between the inclusion limit and the exclusion limit, each solute spends an amount of time in the pore space proportional to its size. The retention volume for a solute is... 

The effects of various pore-size distributions, including Gaussian, rectangular distributions, and continuous power-law, coupled with an assumption of cylindrical pores and mass transfer resistance on chromatographic behavior, have been developed by Goto and McCoy [139]. This study utilized the method of moments to determine the effects of the various distributions on mean retention and band spreading in size exclusion chromatography. 

In fundamental SEC studies retention is often described in terms of a distribution coefficient. The theoretical distribution coefficient Kg is defined as the ratio of solute concentration inside and outside of the packing pores under size exclusion conditions. The experimental distribution coefficient as defined in Equation 1, is a measurable quantity that can be used to check the theory. 

These high performance size exclusion separations of alpha-chymotrypsin SI and myosin light chains compare favorably with those achieved by ion exchange chromatography but require only a fraction of the time to accomplish. Furthermore, the very short retention times allow for separation of these labile proteins at room temperature, whereas operation at 0-40 C would otherwise be mandatory to avoid the loss of enzymatic activity. 

ISEC is a size-exclusion chromatography technique, in which the stationary phase is the CFP to be to characterized [16-18] and the eluates are geometrically well-defined steric probes. From the determined retention volumes in a given solvent and on the basis of suitable morphological models, ISEC analysis provides the... 

Principles and Characteristics Liquid chromatography is the generic name used to describe any chromatographic procedure in which the mobile phase is a liquid. It may be classified according to the mechanism of retention in adsorption, partition, size-exclusion, affinity and ion-exchange (Scheme 4.4). These mechanisms form the basis for the chromatographic modes of... 

Fig. 51 The experimental curve of the molecular weight distribution of a PpPTA polymer dissolved in sulphuric acid determined with size-exclusion chromatography. The relation between molecular weight and retention time t (in minutes) 10log(Mw)=0.345-0.1321 1. The position of the vertical line at f=42 min corresponds with Mw=6,200... 

Non-silica-based RP-HPLC stationary phases have also been developed and their separation capacity has been compared with those of silica-based ones. The porous structure of crosslinked polymer gels may be responsible for the markedly different selectivity and retention characteristics. Up till now, the mode of separation on polymer stationary phases is not entirely understood at the molecular level. It has been established that the size-exclusion effect may influence the retention of analyses on polymer gels. 

The data prove that the retention order of anthocyanins deviates from each other in HPLC and TLC suggesting the involvement of a different retention mechanism. It was stated that the preseparation of anthocyanins by size-exclusion chromatography is a prerequisite of the successful preparative separation by RP-HPLC [244],... 

Size exclusion is the simplest form of chromatography, in which retention depends only on the permeation of analyte into and out of the pore system of the stationary phase. In contrast to other modes of chromatography, such as reversed phase or... 

Figure 2.1 Exploded views showing the nonporous membrane size-exclusion phenomenon in the uptake and loss of organic compounds. Middle illustration shows the movement of contaminant molecules through transient pores in the membrane and retention (membrane exclusion) of much larger lipid molecules. Upper illustration shows similarly scaled space-filled molecular models of some organic contaminants and triolein, along with the hypothetical polymer pore (transient) size. Reprinted with permission from the American Petroleum Institute (Huckinset al., 2002).

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