Development and characterization of molecularly imprinted polymer microspheres for the selective detection of kaempferol in traditional Chinese medicines

In the present work, microwave heating was applied to the preparation of kaempferol molecularly imprinted polymer (MIP) microspheres, resulting in much shorter polymerization times. The MIP microspheres were demonstrated with a narrow diameter distribution of 6–9 μm and a spherical shape. The average diameter of 50 microspheres was 8 μm. The results of the morphology observation, the static adsorption performance and the selectivity performance of the MIP microspheres were all superior to that of the MIPs prepared by conventional heating. The imprinting efficiency of the MIP microspheres was 5.0 and 4.2, which were prepared by microwave heating and conventional heating respectively. MIPs prepared by microwave heating were used as sorbent for solid phase extraction and the elution efficiency of kaempferol was 93.1%. The MIPs coupled with solid phase extraction were used for the extraction of kaempferol from Portulaca oleracea L. and Alpinia officinarum. The regression equation was A = −76437.921 + 1.619 × 107C with correlation coefficients of R = 0.9997. The linearity range was 4.5–200 mg L−1 and the limit of detection was 8.0 μg g−1. The recoveries were 90.2% and 88.0% and the RSDs were 1.21% and 1.18% respectively. The results indicated that the proposed MIPs can be favorably used for the extraction of kaempferol in traditional Chinese medicines.