Microwave-assisted ionic liquid microextraction combined with high performance liquid chromatography for the determination of naphthoquinones from Arnebia euchroma (Royle) Johnst

A simple, rapid, and green microwave-assisted ionic liquid microextraction was established and applied to the extraction of naphthoquinones in Arnebia euchroma (Royle) Johnst., including shikonin, acetylshikonin, and beta,beta '-dimethylacrylshikonin. In this study, 100 mu L of 1-hexyl-3-methylimidazolium hexafluorophosphate ([C(6)mim][PF6]) was used as extraction solvent. After the sample powder and ionic liquid were mixed homogeneously by the vortex, microwave extraction was performed. The sample extract was diluted with methanol and then filtered. Finally, the resulting solution was separated and determined by high performance liquid chromatography-diode array detection. In this work, the experimental parameters affecting the extraction yields, including size of sample particle, sample amount, type and volume of ionic liquid, microwave power, and time were optimized. The experimental results showed that the compounds have a good linear relationship (r > 0.9999). The limits of detection and quantification were 5.0-19.2 ng mL(-1) and 16.7-63.9 ng mL(-1). The spiked recoveries were between 76.95% and 93.55%. The intra-day and inter-day precision were lower than 3.14% and 8.53%, respectively. Compared with ultrasound-assisted extraction and soxhlet extraction, the present method consumed less sample, extraction solvent, and extraction time. So, the present method can be used for the extraction and determination of naphthoquinones in Chinese herbal medicine.