Hydrodynamic Chromatography: The Underutilized Size-Based Separation Technique

Abstract

Hydrodynamic chromatography (HDC) is a size-based liquid chromatographic technique with similar applications as size exclusion chromatography (SEC) and flow field flow fractionation (flow FFF). Separation in HDC is induced within the parabolic flow velocity profile in an open tube or in the interstitial spaces of a packed column, whereby analytes preferentially sample the various streamlines of flow based on size and as a result the larger analytes elute prior to the smaller ones. HDC experimental set-ups can utilize a range of detection methods, e.g., refractive index (RI), UV, multi-angle static light scattering (MALS), quasi-elastic light scattering (QELS), differential viscometry and inductively coupled plasma mass spectrometry (ICP-MS), coupled in various combinations. Here, we discuss the historical use of single-detector HDC for the determination of polymer/particle size using calibration standards, followed by the more modern-day approach of multi-detector HDC, which can be used for the determination of polymer/particle molar mass, size, shape and compactness. Finally, we provide a perspective on the potential and limitations of HDC as a technique for the characterization of polymers and particles.