Application of Zeolites in High-Performance Liquid Chromatography

Abstract

Inorganic zeolites, or microporous crystalline aluminosilicates, possess high porosity, well-developed specific surface area, uniform pores, and ion-exchange properties, which determine their molecular sieve and adsorption properties. The use of zeolites as catalysts, desiccants for solvents and gases, and selective adsorbents for the separation of low-molecular-weight compounds is widely known. Zeolites also serve extensively as packing materials for chromatographic columns in gas-adsorption chromatography. However, their application to high-performance liquid chromatography (HPLC) is less recognized. In HPLC, the retention of adsorbates depends not only on adsorption interactions but also on the molecular sieve effect in the micropores and kinetically selective effects. Additional interactions with the mobile phase components alter the thermodynamic parameters of the adsorbates interaction with the zeolite, decrease effective pore size, and hinder the diffusion of the separated compounds into the adsorbent’s pores. Despite these challenges, zeolites remain promising adsorbents due to their strictly determined pore size (d_pore) and geometry, as well as their customizable polarities, which ensure high selectivity for the separation of low-molecular-weight compounds. The most promising zeolites for HPLC are wide-pore zeolites (d_pore 0.6–0.8 nm) with 8, 10, 12, and 14-member ring channels. This review offers a concise overview of the classification, composition, and structure of zeolites and their impact on the adsorption properties of these adsorbents. Data on the use of zeolites in HPLC are also systematized.