3.2.4. Solid–liquid ratioLarge volumes of extraction solvent would lead to unnecessarywaste, while small volumes may lead to incomplete extraction.To evaluate the influence of solid–liquid ratio on extraction effi-ciency of the targeted analytes, a series of experiments wereperformed with different solid–liquid ratios (1:6, 1:8, 1:10, 1:13and 1:16 g mL−1). As shown in Fig. 2d, the extraction efficiencydecreased dramatically when the solid–liquid ratio changed from1:6 to 1:16. The reasons might be that the viscosity influenced thesolvent permeation for the targeted compounds, and then weak-ened the dissolution of flavonoids [29]. Hence, a solid–liquid ratioof 1:6 was adopted in this study.