Size exclusion chromatography determine relative molecular weights

Size-exclusion chromatography (sec) easily and rapidly gives the complete molecular weight distribution and any desired average (6). Thus, it has become the technique of choice for determining molecular weights despite its relatively high initial cost. 

The ideal packing should be relatively large in diameter, 80-100 nm, and be available with a pore size range from 500 to 10,000 A. The ores should be uniform in size distribution and shallow to reduce diffusion times. Improvements of this type will lead to the use of size exclusion chromatography for particle size determinations in the routine manner in which it is now employed for molecular weight determinations. 

Advances in size-exclusion chromatography, coupled with refractive index, absorption, viscosity, and lightscattering detectors, and MALDI-ToFMS, have made it possible to accurately determine molecular weight distribution (oligomer profiling), even at the relatively low values of polymeric additives (up to about 5000 Da). Advances in column design, e.g. high-resolution PS/DVB columns (> 105 plates m-1) mean that SEC can provide a valuable alternative to conventional HPLC techniques for the separation of small molecules. 

A wide variety of polymers have been analyzed by gel-permeation, or size-exclusion, chromatography (sec) to determine molecular weight distribution of the polymer and additives (86—92). Some work has been completed on expanding this technique to determine branching in certain polymers (93). Combinations of sec with pyrolysis—gc systems have been used to show that the relative composition of polystyrene or acrylonitrile—polystyrene copolymer is independent of molecule size (94). Improvements in gpc include smaller cross-linked polystyrene beads having narrow particle size distributions, which allow higher column efficiency and new families of porous hydrophilic gels to be used for aqueous gpc (95). 

The range of the (molecular) size of the analytes usually exceeds that which can be determined by classical laboratory analytical methods such as size exclusion chromatography, etc. [351]. Reports on investigated substances are widespread and cover applications such as the separation and characterization of proteins [450] and enzymes [240, 241], of viruses [132], the separation of human and animal cells [50, 51], the isolation of plasmid DNA [367], and the molecular weight and particle size distribution of polymers [216,217]. The approach is relatively new in biotechnology therefore, practical experiences are not yet abundant. Langwost et al. [229] have provided a comprehensive survey of various applications in bio-monitoring. 

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