Fig. 1

Chemical structures of the analytes and IS. a: Paeoniflorin (PF); b: albiflorin (AF); c: liquiritin (LT); d: isoliquiritin (ILT); e: liquiritin apioside (LA); f: isoliquiritin apioside (ILA); g: glycyrrhizic acid (GL); h: glycyrrhetinic acid (GA); IS: geniposide