Abstract: Hollow fiber liquid phase microextraction (HFLPME) coupled with high performance liquid chromatography (HPLC) has been developed to analyze the emodin and its metabolites in plasma and urine samples. The abilities of the absorption and metabolism for the active components in traditional Chinese medicines between the male and female rats were compared, and the biological metabolism and transmutation of the analyte were detailed discussed. Emodin and its metabolites in plasma and urine samples were extracted into n-octanol (acceptor) in hollow fiber. The acceptor phase was dried and dissolved by 50 μL methanol and then analyzed by HPLC. Under the optimal conditions, the linearities of the analytes were all very good in biological samples (r＞0.9960), the detection limits of the analytes were within the ranges of 0.1~3.0 μg/L. The enrichment factors were 12.2 to 26.3. The relative standard deviations for intra-day and inter-day precision were lower than 11.0%. The average recoveries of the analytes in plasma and urine samples were all in the range of 97.9% to 103%. HFLPME-HPLC can eliminate interference from complex biological samples, improve the sensitivity and reduce the detection limit, thus this method is suitable for the determination of trace compounds in complex sample.

Key words: biological transformation, emodin and its metabolites, high performance liquid chromatography (HPLC), hollow fiber liquid phase microextraction