The fabrication of carboxylic acid-functionalized porous layer open tube column and its application in hydrophilic interaction chromatography for small polar molecules

The porous layer open-tube (PLOT) columns, which were characterized by their considerable specific surface area and high permeability, have attracted a growing attention from researchers in liquid chromatography. In this work, a hydrophilic PLOT column rich in carboxylic acid functional groups was successfully synthesized in capillary with an inner diameter of 200 µm by thermally initiated aqueous two-phase polymerization. Methacrylic acid (MAA) areas monomers that responsible for the introduction of polar functional groups, and poly(ethylene glycol) diacrylate (PEGDA) are as cross-linker. The optimized PLOT column has a uniform, moderately thick porous layer, which is tightly bonded to the inner wall without any detachment. The hollow structure gives the PLOT column good permeability, which facilitates fast mass transfer. The systematical evaluations of the resulting PLOT columns were performed by using polar analytes including nucleosides, bases, amides, phenols and carboxylic acids. Those results demonstrated excellent separation performance for the small polar molecules. Compared to the poly(PEGDA) PLOT column, the hydrophilic retention of analytes on poly(PEGDA-co-MAA) porous layer open-tube column is significantly improved by the introduction of carboxylic acids. Furthermore, with modified nucleosides and chlorophenols being disease markers and the persistent pollutant of wide concern, respectively, the separation was optimized and the linear range of the quantitative analysis was examined for both targets. which indicates the potential application of such PLOT column for analysis of real samples.