Simultaneous determination of curcuminoids in Curcumae Longae Rhizoma and turmeric tea using liquid-phase microextraction based on solidification of floating deep eutectic solvent drop

Abstract

A simple and efficient liquid-phase microextraction procedure has been developed based on solidification of floating deep eutectic solvent (DES) drop for simultaneous separation and preconcentration of active curcuminoids in Curcumae Longae Rhizoma and turmeric tea. In this work, a hydrophobic and low-density DES prepared from tetrabutylammonium chloride and decanoic acid as extractant was injected into the sample phase, and a cloudy solution was formed by magnetic stirring at 40 °C. After extraction, the floating and reaggregated DES drop was recovered through solidification for high performance liquid chromatography analysis. The important extraction variables were optimized including extraction solvent type and consumption, sample phase pH, salt amount, stirring rate, extraction time and temperature. Under the optimal conditions, good responses were presented with detection limits of 7.0 × 10−5, 7.0 × 10−5, 9.0 × 10−5 mg/L, and enrichment factors of 608, 621, and 848 for bisdemethoxycurcumin, demethoxycurcumin and curcumin, respectively. Satisfactory accuracies (recoveries 84.6–116.8%) and precisions (relative standard deviations 1.4–4.2%) were also obtained. The proposed method was successfully applied for extraction and determination of three curcuminoids in real herbal and dietary supplement samples.