Chapter 2
Nonsize Exclusion Effects in High-Performance Size Exclusion Chromatography
Downloaded by AUBURN UNIV on December 26, 2017 | http://pubs.acs.org Publication Date: October 2, 1987 | doi: 10.1021/bk-1987-0352.ch002
Howard G. Barth Hercules Inc., Research Center, Wilmington, DE 19894
This chapter presents an overview of nonideal size exclusion chromatographic (SEC) behavior which may occur during high performance SEC. If not eliminated or at least reduced, these effects may lead to erroneous molecular weight distribution results. Enthalpic interactions between polymer and packing are discussed in detail as well as intramolecular electrostatic effects that occur with polyelectrolytes. Concentration effects, that is, viscous fingering and macromolecular crowding, are reviewed. Other nonsize exclusion effects, which may exist especially in high performance systems, are presented including polymer shear degradation, ultrafiltration, and polymer chain orientation. Size exclusion chromatography i s a unique separation technique based on molecular size (hydrodynamic volume) differences among solutes. The d i s t r i b u t i o n c o e f f i c i e n t K of an eluting solute i s defined as d
K
d
= (V - V )/Vi e
(1)
0
where K i s the r a t i o of the solute concentration within the pores of the packing to the solute concentration in the i n t e r s t i t i a l volume, V i s the elution volume of the polymer, and V and are the i n t e r s t i t i a l and pore volumes of the packed column, respectively. The physical significance of the values that K can have is as follows: d
e
0
d
Complete exclusion of the solute from the pores of the packing. 0
