Multi-detector hydrodynamic chromatography of colloids: following in Hamish Small's footsteps.

Hamish Small, scientist extraordinaire, is best known as the inventor of both ion chromatography and hydrodynamic chromatography (HDC). The latter has experienced a renaissance during the last decade-plus, thanks principally to its coupling to a multiplicity of physicochemical detection methods and to the structural and compositional information this provides. Detection methods such as light scattering (both multi-angle static and dynamic), viscometry, and refractometry can combine to yield insight into macromolecular or colloidal size, structure, shape, and molar mass, all as a function of one another and continuously across a sample's chromatogram. It was the author's great fortune to have known Hamish during the last decade of his life, before his passing in 2019. Here, a brief personal recollection is followed by an introduction to HDC and its application, in quadruple-detector packed-column mode, to the analysis of a commercial colloidal silica with an elongated shape.