Fabrication of microporous organic network incorporated monolithic column for improved high performance liquid chromatographic separation of small molecules.

BACKGROUND: As a class of boomingly developed porous material, microporous organic networks (MONs) demonstrated great prospects in HPLC because of their unique structures and excellent stabilities. However, the agglomerated, irregular, and sub-micron sized MONs obtained via the traditional synthesis methods inevitably cause high column pressure and low column efficiency, rendering the main obstacles for their applications in HPLC. Monolithic column has the characteristics of continuous porous structure, fast mass transfer rate, excellent permeability, and low column pressure. Therefore, the integration of MONs with monolithic column should be a potential way to extend the widespread applications of MONs in HPLC.

RESULTS: In this work, we reported the first example of fabricating MON incorporated monolithic columns by employing methacrylic acid as the monomer, ethylene dimethacrylate as the cross-linking agent, and polyethylene glycol-6000 as the porogen for the improved HPLC separation of small organic molecules. Effects of preparation conditions for MON incorporated monolithic column, sample loading mass, column temperature, and mobile phase composition were studied in detail. MON monolithic column after MON incorporation exhibits improved permeability, column efficiency, hydrophobicity, and specific surface area. Diverse small organic molecules such as polycyclic aromatic hydrocarbons, alkylbenzenes, acidic phenols, basic amines, phenylurea herbicides, parabens, phthalates, and flavonoids were successfully separated on MON incorporated monolithic column (50.0 mm length × 4.6 mm i.d.). MON incorporated monolithic column also provided better resolution and selectivity than C18 packed column.

SIGNIFICANCE: This work reported the first combination of MON and monolithic column for efficient HPLC separation of variety small organic compounds with good resolution, selectivity, and precisions based on typical reversed phase mechanism. The experimental results demonstrated the great potential of MON incorporated monolithic column for enhanced HPLC separation of small organic compounds and could extend the new applications of MONs in separation science.