Viscometric Detection in Size-Exclusion Chromatography: Principles and Select Applications

Abstract

Size-exclusion chromatography (SEC) has benefitted from commercially available on-line viscometers for 30 years now. Initial (and continued) interest was mostly in applying the universal calibration concept to obtain molar mass averages and distributions of macromolecules for which no appropriate calibration standards existed, and in obtaining long-chain branching information such as branching number and frequency. During the last three decades, viscometry has shown itself to be able to do much more than this, especially (but not exclusively) when employed in multi-detector set-ups which include light scattering photometers. The purpose of this review is to demonstrate the power of viscometry detection in SEC, through applications which showcase the extreme or, simply, the unusual, oftentimes as encountered by the author. A brief review of history and theory is thus followed by examples of the role of viscometry in the SEC characterization of, among others, solutions with negative viscosity, polymers which undergo morphological transformations during growth, polysaccharides with molar mass distributions extending into the hundreds of millions of g mol−1, and spectroscopically invisible macromolecules.