Chapter 3 Electrostatic Effects

Abstract

Publisher Summary This chapter describes the elution of low molecular weight (MW) salts. The chapter describes the behavior of synthetic polyelectrolytes, treating polycations separately, because these compounds pose special difficulties. The role of electrostatic effects in the size-exclusion chromatography (SEC) of proteins is also described. The chapter also discusses models employed for the investigation of semi-quantitatively treat electrostatic effects. The elution volume of low MW salts is investigated as a function of the concentration injected, the ionic strength (I) of the mobile phase, and the chemical nature of the analyte, for a wide range of packings, including Sephadex, unmodified silica, and derivatized glass and silica. Low MW compounds are used to probe both hydrophobic and electrostatic solute-substrate interactions for a variety of derivatized silica packings. For Synchropak TM , porous silica derivatized with glyceryl–propylsilane (Synchrom), multivalent anions exhibit K SEC values decreasing from 0.9 to 0.4 as I (pH 7 phosphate buffer) diminishes from 0.2 to zero. While K SEC increases with I, it does not attain unity, even at I = 2.