Selective Solid-Phase Extraction of Glabridin from Licorice Root using Molecularly Imprinted Polymer

A selective molecularly imprinted solid-phase extraction procedure was developed for the selective separation of glabridin from licorice roots samples. The molecularly imprinted polymers (MIPs) synthesized in ethanol-dodecanol solution show high affinity to glabridin in aqueous environment and the affinity can be controlled by adjusting the intensity of the eluents. By using water-methanol (60:40, v/v) and acetonitrile-trifluoroacetic acid (99.5:0.5, v/v) as washing and eluting solvents, most interferences originating from licorice matrix were eliminated. The extracts were sufficiently clean to be directly injected into HPLC for further chromatographic analysis. Good linearity was obtained from 0.4 to 500mg/L (r=0.999) with the relative standard deviations less than 3.6%. The mean recoveries of glabridin from licorice were more than 81.8% at three different concentrations and the limit of detection was 0.07mg/L. This method is a viable alternative tool to the existing HPLC methods for analyzing the content of glabridin in licorice samples.