A switchable deep eutectic solvent-based homogeneous liquid–liquid microextraction combined with high-performance liquid chromatography for the determination of flavonoids in shuxuening injection

A homogeneous liquid-liquid microextraction (HLLME) was established based on a switchable deep eutectic solvent (DES) and combined with high-performance liquid chromatography (HPLC) to enrich and determine flavonoids in shuxuening injection (SXNI). The optimal extraction conditions were determined using single factor and Box-Behnken response surface design. Specifically, 3 mL of sample solution was mixed with 150 μL of sDES (<i>N</i>,<i>N</i>-dimethylethanolamine:enanthate, 1 : 1 ratio) and vortexed for 30 s. Subsequently, 100 μL of 5.0 mol L^-1 HCl solution was added and vortexed again for 30 s. Under the optimized conditions, the enrichment factors for quercetin, kaempferol, and isorhamnetin were 30, 33, and 28, respectively. Quercetin had good linearity in the range of 7.5-300 μg mL^-1, kaempferol in the range of 8-320 μg mL^-1, and isorhamnetin in the range of 5-200 μg mL^-1. Good precision (RSD < 4.0%) and acceptable accuracy (spike recovery, 97.13-111.78%) were obtained. The Analytical Greenness Calculator (AGREE) yielded a score of 0.75 for the sDES-HLLME method and the Green Analysis Program Index (GAPI) showed that the method had a low ecological impact. The established sDES-HLLME method is a simple, green, and efficient sample preparation method with broad application prospects for trace analyte extraction from complex substances.