Superficially porous particles in liquid chromatography

Superficially porous particles (SPP) (also known as core-shell, fused-core, partially porous particles, pelicular or solid-core) were conceived by Horvàth in 1967 and subsequently widely developed by Kirkland (who gave them the name fused-core), particularly for the analysis of large molecules such as peptides and proteins. Indeed, due to the low diffusion coefficients of these macromolecules, the chromatographic performance (in kinetic terms) of conventional porous supports is unacceptable, inducing very broad peaks that limit both the sensitivity of the analysis and its resolving power. The first developments of these superficially porous particles were carried out with particles having external diameters of a few tens of micrometers. The body of the particles was then made up of a non-porous phase coated with a very thin layer of porous support (less than 1 μm thick) of the same nature as traditional chromatographic supports. Later, these superficially porous particles were marketed with an external diameter of 5 μm to improve kinetic performance, and always with the aim of analyzing proteins or other large molecules.

In the pharmaceutical field, but also in other areas such as the environment, toxicology or agri-food, it is now necessary to develop increasingly high-performance analysis methods in terms of speed and separative power. Moreover, the nature of the compounds to be analyzed is highly diverse, ranging from small molecules (100 to 1,000 Da) to large macromolecules (proteins, monoclonal antibodies of the order of 150 kDa), and matrices can be highly complex. Various chromatographic supports have been developed at XXI ^e century to meet these demands. Monolithic stationary phases based on silica or polymers were...