Kaempferol Molecularly Imprinted Monolithic Columns Prepared by a Surface Imprinting Method and Their Applications to Direct Separation of Flavonoids From Ginkgo Leaves by Liquid Chromatography

In this study, kaempferol molecularly imprinted monolithic columns (MIMCs) featuring a homogeneous pore structure and high separation ability were successfully prepared by surface imprinting on silica monoliths. These columns were then used to separate flavonoids from the hydrolysate of Ginkgo leaves. The preparation process involved three simple steps: preparation of silica monoliths, functionalization of the silica surface, and polymerization of the imprinting system onto the silica surface. The resulting MIMCs exhibited a homogeneous pore structure, high surface area (>100 m²/g), high porosity (ca. 74%), and good permeability (3.0 - 3.9 × 10^-15 m²). The chromatographic separation performance of the MIMCs prepared on amino-functionalized silica monoliths was significantly superior to those prepared on thiol and vinyl-functionalized silica monoliths. The MIMCs prepared on amino-functionalized silica monoliths (I.D. 4.6 × 20 mm) could nearly achieve baseline separation of four structurally similar flavonoids: genistein, kaempferol, isorhamnetin, and quercetin. In addition, these MIMCs exhibited excellent selectivity in the chromatographic separation of flavonoids from the hydrolysate of Ginkgo leaves. However, when used as SPE adsorbents, the MIMCs prepared on thiol and vinyl-functionalized silica monoliths were superior to those on amino-functionalized silica monoliths in terms of purification of flavonoids from the Ginkgo hydrolysate. This study may be of instructive significance to the facile preparation of MIMCs for the high-selectivity separation and analysis of target components in complex natural systems.