Online preconcentration and determination of anthraquinones in Cassiae Semen tea by salting-out assisted liquid‒liquid extraction coupled with dynamic pH junction-sweeping-large volume sample stacking in capillary electrophoresis

A new strategy by coupling salting-out assisted liquid‒liquid extraction with dynamic pH junction-sweeping-large volume sample stacking in capillary electrophoresis was proposed for extraction, online preconcentration, separation and determination of trace anthraquinones in food samples. Based on the complementary advantages of salting-out assisted liquid‒liquid extraction and online capillary electrophoresis stacking, the strategy allowed for rapid extraction and sensitive analysis of anthraquinones in aqueous matrix samples. Under the optimized conditions, the proposed strategy showed good linearity (100–3000 ng/mL, r2 ≥ 0.993) with a low detection limit of 30–40 ng/mL. Sensitivity enhancement factors of up to 468-fold were reached with the optimized dynamic pH junction-sweeping-large volume sample stacking using capillary electrophoresis with a UV detector. As a proof-of-concept study, this strategy was successfully applied for analysing anthraquinones in Cassiae Semen tea, which demonstrated good potential for the efficient and sensitive determination of weakly acidic analytes in complicated sample matrices.