Size-exclusion chromatography particles

After receiving his doctorate, he joined the Monsanto Company in St. Louis as a senior research chemist and carried out research on the characterization and material properties of exploratory polymers and composites. While he was at Monsanto, his research interests focused on molecular weight characterization, particularly by size-exclusion chromatography. Recently, his research has focused on size-exclusion chromatography, particle size distribution analysis, cure chemistry and physics, and the application of computers in the polymer laboratory. He is the author of more than 100 publications, is credited with three patents, and has edited or co-edited 10 volumes in the ACS Symposium Series and co-edited two volumes in the Advances in Chemistry series. 

Wei G T, Liu F K and Wang C R C 1999 Shape separation of nanometre gold particles by size-exclusion chromatography Anal. Chem. in press... 

Two classes of micron-sized stationary phases have been encountered in this section silica particles and cross-linked polymer resin beads. Both materials are porous, with pore sizes ranging from approximately 50 to 4000 A for silica particles and from 50 to 1,000,000 A for divinylbenzene cross-linked polystyrene resins. In size-exclusion chromatography, also called molecular-exclusion or gel-permeation chromatography, separation is based on the solute s ability to enter into the pores of the column packing. Smaller solutes spend proportionally more time within the pores and, consequently, take longer to elute from the column. 

SI units stands for Systeme International d Unites. These are the internationally agreed on units for measurements, (p. 12) size-exclusion chromatography a separation method in which a mixture passes through a bed of porous particles, with smaller particles taking longer to pass through the bed due to their ability to move into the porous structure, (p. 206)... 

Column Si. Size-exclusion chromatography columns are generally the largest column on a process scale. Separation is based strictly on diffusion rates of the molecules inside the gel particles. No proteins or other solutes are adsorbed or otherwise retained owing to adsorption, thus, significant dilution of the sample of volume can occur, particularly for small sample volumes. The volumetric capacity of this type of chromatography is determined by the concentration of the proteins for a given volume of the feed placed on the column. 

D. Application of Monosized Polymeric Particles in Size Exclusion Chromatography... 

A trend in chromatography has been to use monosized particles as supports for ion-exchange and size-exclusion chromatography and to minimize the column size, such as using a 15 X 4.6-mm column packed with 3-/rm polymer particles for size exclusion chromatography. The more efficient and lower back pressure of monosized particles is applied in the separation. 

A. Development of Silica Particles for High-Performance Size Exclusion Chromatography (HPSEC)... 

Modern SEC columns are packed with material other than polystyrene gels, such as porous silica particles or highly cross-linked styrene-divinylbenzene copolymers. Because of improvements in speed and resolution, the term SEC is sometimes replaced by the term high-performance size-exclusion chromatography (HPSEC). 

High-performance size exclusion chromatography is used for the characterization of copolymers, as well as for biopolymers (3). The packings for analyses of water-soluble polymers mainly consist of 5- to 10-/Am particles derived from deactivated silica or hydrophilic polymeric supports. For the investigation of organosoluble polymers, cross-linked polystyrene beads are still the column packing of choice. 

The Styragel family of packings represents the classical packing of size exclusion chromatography (2). It is based on cross-linked styrene-divinylbenzene particles. Pore sizes range from around 20 A for the Styragel... 

The two techniques differ in that HDC employs a nonporous stationary phase. Separation is affected as a result of particles of different size sampling different velocities in the interstitial spaces. Size exclusion chromatography is accomplished by superimposing a steric selection mechanism which results from the use of a porous bed. The pore sizes may vary over a wide range and the separation occurs as a result of essentially the same processes present in the gel permeation chromatography of macromolecules. 

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. 

Kulin, L.-I., Flodin, P., Ellingsen, T., and Ugelstad, J., Monosized polymer particles in size exclusion chromatography. I. Toluene as solvent, /. Chromatogr., 514, 1, 1990. 

Stegeman, G., Kraak, J. C., and Poppe, H., Hydrodynamic and size-exclusion chromatography of polymers on porous particles, ]. Chromatogr., 550, 721, 1991. 

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