Matrix solid-phase dispersion extraction followed by HPLC-diode array detection method for the determination of major constituents in a traditional Chinese medicine Folium isatidis (Da-qing-ye)

A simple and low-cost method based on matrix solid-phase dispersion (MSPD) extraction, HPLC separation, and diode array detection has been developed for the determination of indigo and indirubin in Folium isatidis. The experimental parameters that may affect the MSPD method, including dispersing sorbent, ratio of dispersing sorbent to sample, elution solvent, and volume of the elution solvent were examined and optimized. The optimized conditions were determined to be that C18 was used as dispersing sorbent, the ratio of C18 to sample mass was selected to be 4:1, and 10 mL of N,N-dimethyl formamide was used as elution solvent. The highest extraction yields of the two compounds were obtained under the optimized conditions. The method showed good linearity (r > 0.9995) and precision (RSD < 3.0%) for indigo and indirubin, with the limits of detection of 18 and 22.5 ng/mL, respectively. The recoveries were in the range of 90.33100.74% with RSDvalues ranging from 1.7 to 3.6%. Comparing to ultrasonic and Soxhlet methods, the proposed MSPD procedure was more convenient and less time-consuming with reduced requirements on sample and solvent amounts. The proposed procedure was applied to analyzed three real samples that were collected from different localities.