Advancements in the preparation of high-performance liquid chromatographic organic polymer monoliths for the separation of small-molecule drugs

Abstract

The various advantages of organic polymer monoliths, including relatively simple preparation processes, abundant monomer availability, and a wide application range of pH, have attracted the attention of chromatographers. Organic polymer monoliths prepared by traditional methods only have macropores and mesopores, and micropores of less than 50 nm are not commonly available. These typical monoliths are suitable for the separation of biological macromolecules such as proteins and nucleic acids, but their ability to separate small molecular compounds is poor. In recent years, researchers have successfully modified polymer monoliths to achieve uniform compact pore structures. In particular, microporous materials with pores of 50 nm or less that can provide a large enough surface area are the key to the separation of small molecules. In this review, preparation methods of polymer monoliths for high-performance liquid chromatography, including ultra-high cross-linking technology, post-surface modification, and the addition of nanomaterials, are discussed. Modified monolithic columns have been used successfully to separate small molecules with obvious improvements in column efficiency.

Surface-modified three-dimensional graphene nanosheets as a stationary phase for chromatographic separation of chiral drugs

“…The majority of reported attempts to use graphene or graphene oxide for chromatographic stationary phases were not focused on chiral separation (see Table 3 ). Most of them were different variants of graphene or GO-doped organic polymer monoliths 41 , 47 . The previous reported attempts utilizing graphene or graphene oxide-based materials for chiral separation are not directly comparable with MOD1 and MOD3 materials, because they were designed and tested for other, non-HPLC separation techniques.…”

“…The immobilized silica gel-based CSPs work with a wide spectrum of solvents and are chemically stable, but these superior performance parameters are the result of complex multi-step fabrication processes; therefore, the price of these CSPs is high 3 , 4 . The reported carbon based CSPs with chiral CNTs are complex in fabrication, and have significant limitations as a result of the use of organic polymer monoliths 25 , 41 , 47 . The demonstrated chiral separators utilizing graphene or graphene oxide also have a variety of limitations: they either use weakly attached chiral molecules 29 – 35 and cannot be chemically stable in many important organic solvents, or completely adsorb and block one of the enantiomers during separation 39 , 40 .…”

“…The reported carbon-based CSPs using chiral CNT-doped organic polymer monoliths are complex in fabrication. They have limitations related to insufficient control of organic monolith porosity during fabrication, the effect of swelling of organic monoliths in organic solvents, as well as complications and costs related to the need for small diameter (tens-hundreds of μm) capillary tubes and dramatically low possible flow rates (μl/min or less) through the separation columns 25 , 41 . The demonstrated chiral separators utilizing graphene or graphene oxide have a variety of limitations: they either use weakly attached (adsorbed) chiral molecules 29 – 35 and, as a result, cannot be stable in many important organic solvents, or they completely adsorb and block one of the sample enantiomers during separation, being specifically designed for such a non-chromatographic type of separation 39 , 40 .…”

Eco-friendly production of metal nanoparticles immobilised on organic monolith for pepsin extraction

“…Currently, various methods are employed for modifying nanoparticle monoliths they include attachment of nanoparticles to preformed monolith surfaces, copolymerizing functionalised monomer nanoparticles, and embedding nanoparticles within the monolithic matrices. Even though copolymerization and embedding constitute direct and simplest methods, they lead to spread of nanoparticles in the entire monolithic matrix and thus most are inaccessible on the pore surfaces for desired interactions [27][28][29] .…”

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].…”