Determination of Anthraquinone Derivatives in Chang-Qing Tea by Using Cloud-Point Extraction and High-Performance Liquid Chromatography

In this paper, a cloud-point extraction method was developed for the determination of five anthraquinone derivatives in Chang-Qing tea by high-performance liquid chromatography. The optimum conditions for micelle extraction were obtained as follows—15% (w/v) Genapol X-080 as extractant, pH 3.5, liquid/solid ratio 80, and extraction time, 40 min. For cloud point preconcentration, 20% (w/v) NaCl was added, and the solution was incubated at 55 °C for 30 min. The detection limits for the five anthraquinone derivatives were in the range of 0.55–3.30 ng ml−1. Average recoveries for the anthraquinone derivatives at three spiked levels were in the range of 84.3–104.1%. Relative standard deviations for six replicate determinations of Chang-Qing tea sample were below 2.39. The established method has been successfully applied to the determination of anthraquinone derivatives in Chang-Qing tea products from three different manufacturers.