Irradiation timeIn order to select the optimal irradiation time, extractions werecarried out at 400 W for different irradiation times (max: 120 s).As shown in Fig. 2a, when the irradiation time increased from5 s to 90 s, the extraction efficiency of baicalin and wogonoside increased, but the extraction efficiency of baicalein and wogoninde creased. The possible reason was that the structures of baicaleinand wogonin were more thermally unstable than baicalin andwogonoside [28]. When the irradiation time increased from 90 to120 s, the extraction efficiency of the four analytes did not signif-icantly change. Thus, 90 s was selected as the optimal irradiationtime for all subsequent experiments.