This article is aimed at providing a review of the progress made in the field over the period 2011 to present in order to expand in parts on two previous reviews (S. Karenga and Z. El Rassi, Electrophoresis, 2011, 32, 90-104; D. Gunasena and Z. El Rassi, Electrophoresis, 2012, 33, 251-261). In brief, this review article describes progress made in nonpolar and polar monoliths used in reversed phase HPLC and CEC (RPC/RP-CEC) and in hydrophilic interaction liquid chromatography/CEC (HILIC/HI-CEC), respectively. This article is by no means an exhaustive review of the literature; it is rather a survey of the recent progress made in the field with 69 references published on nonpolar and polar polymeric monoliths.

This review article is a continuation of the previous reviews on the area of monolithic columns covering the progress made in the field over the last couple of years from the beginning of the second half of 2014 until the end of the first half of 2016. It summarizes and evaluates the evolvement of both polar and nonpolar organic monolithic columns and their use in hydrophilic interaction LC and CEC and reversed-phase chromatography and RP-CEC. The review article discusses the results reported in a total of 62 references.

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Two polar silica bonded stationary phases were prepared by first functionalizing the silica surface with γ-glycidoxypropyltrimethoxysilane, which was then reacted with TRIS to yield a polyhydroxy surface that also has secondary amine functionalities. This step produced the singly layered TRIS-silica column, a cationic hydrophilic column. The TRIS-silica surface was further coated with a layer of chondroitin sulfate A (CSA) yielding the doubly layered hydrophilic CSA-TRIS-silica column. The adsorbed CSA layer provided enhanced hydrophilicity and multi-mode interactions with polar solutes leading to different retention behavior and selectivity compared to the singly layered TRIS-silica column. The anionic sulfate and carboxylate groups in the CSA coating are electrostatically attracted by the cationic TRIS-silica surface yielding a relatively stable physically anchored CSA layer under HILIC elution conditions. The CSA-TRIS-silica column exhibited dual cationic and anionic character with mobile phases at pH ∼3.0 and pH > 4.5, respectively. When comparing solute retention observed on both columns under identical elution conditions, the k values of neutral and cationic solutes were significantly higher on the more hydrophilic doubly layered CSA-TRIS-silica column whereas anionic solutes showed lower k values due to the electrostatic repulsion from the CSA layer.