Recent Progress in Monolithic Silica Columns for High-Speed and High-Selectivity Separations

Abstract

Monolithic silica columns have greater (through-pore size)/(skeleton size) ratios than particulate columns and fixed support structures in a column for chemical modification, resulting in high-efficiency columns and stationary phases. This review looks at how the size range of monolithic silica columns has been expanded, how high-efficiency monolithic silica columns have been realized, and how various methods of silica surface functionalization, leading to selective stationary phases, have been developed on monolithic silica supports, and provides information on the current status of these columns. Also discussed are the practical aspects of monolithic silica columns, including how their versatility can be improved by the preparation of small-sized structural features (sub-micron) and columns (1 mm ID or smaller) and by optimizing reaction conditions for in situ chemical modification with various restrictions, with an emphasis on recent research results for both topics.

In situ silanization for continuous stationary phase gradients on particle packed LC columns

“…Compared to planar substrates and monolithic columns, the time-dependent modication of a traditional LC packed column in situ is much more challenging, not only because of the increased back pressure required for infusion into a packed column, but also because of the high surface area and microporosity of the silica powder. Additionally, porous particle columns have a lower permeability relative to monoliths, 33 which could potentially cause stagnant modication solution and unintentional heterogeneous modication.…”

Immobilization of a phosphonium ionic liquid on a silica monolith for hydrophilic interaction chromatography

“…The latter approach involves gradual modification of the original monolith to obtain the desired stationary phase. A detailed overview of the preparation of inorganic, polymer, or hybrid monolithic columns and their utilization in chromatographic separations can be found in many reviews, see, e.g., [2,3,6,7] for some recent works dealing with the topic.…”

Monolithic Silica Capillary Columns with Improved Retention and Selectivity for Amino Acids

“…On the other hand, the supply of monolithic capillary columns is limited to columns suitable for RPLC, such as the polymer-based ProSwift™ monolithic LC columns, supplied by Thermo Scientific™ (Waltham, MA, USA), the silica-based monolithic columns Chromolith ® CapRod ® capillary LC columns, supplied by Merck KGaA (Darmstadt, Germany), Onyx™ Monolithic C18 column supplied by Phenomenex (Torrance, CA, USA), and, last but not least, a company offering silica-based monolithic columns is GL Sciences Inc. (Tokyo, Japan) with MonoCap series of columns suitable for RPLC, HILIC, and strong-cation-exchange chromatography. Along with an ever-expanding supply of monolithic columns, new monolithic materials which are suitable for highly-specialized separations are being prepared in laboratories around the world [14][15][16][17][18].…”