Selective adsorption of multi-walled carbon nanotubes with liquiritin and isoliquiritin

Selective adsorption of active ingredients liquiritin and isoliquiritin from Glycyrrhiza uralensis Fisch with multi-walled carbon nanotubes (MWNTs) has been studied. Distribution coefficients of liquiritin between ethanol solvent and r-MWNTs or o-MWNTs in 293K is 37.5 and 43.3, while the distribution coefficients of isoliquiritin between ethanol solvent and r-MWNTs or o-MWNTs is 717 and 1080, respectively. It was indicated that the distribution coefficient of isoliquiritin adsorbed by MWNTs was much larger than that of liquiritin, and oxidation treatment of MWNTs could obviously enhance their adsorption ability. The possible reasons that MWNTs can selectively adsorb isoliquiritin other than liquiritin were discussed on the bases of molecular structure of the active ingredients and their interaction with nanotubes.