Hydrophilic interaction chromatography-type sorbent prepared by the modification of methacrylate-base resin with polyethyleneimine for solid-phase extraction of polar compounds.

Hydrophilic interaction chromatography (HILIC)-type sorbents were newly developed for the solid-phase extraction (SPE) of polar compounds. Two methacrylate-base resins with different cross-linking monomers and pore properties were synthesized, and three polyethyleneimines (PEIs) with different molecular weights were modified onto each base resin. In both cases, PEIs with a molecular weight of 10,000 (PEI-10,000) exhibited the highest adsorption properties for polar compounds (uracil, uridine, adenosine, cytidine, and guanosine). To control the water-enriched layer at the surface of the PEI-10,000-modified sorbents, the additive amount of PEI-10,000 in the modified reaction was also optimized. When 10 times the amount of PEI-10,000 to each base resin was added, an improvement in adsorption property was observed. Moreover, the use of a nonaqueous sample solution (100% acetonitrile) during the sample loading process drastically improved adsorption, especially for uracil (about 80%) and adenosine (100%). These results indicate that the formation of a strong water-enriched layer at the surface of sorbents with an effective expression of hydrophilic interaction was an important factor in the adsorption properties of polar compounds in HILIC mode-SPE.