The rhubarb decoction samples (100 L) were applied to the extraction C18 cartridge, preconditioned successively with 3mL of methanol and 3 mL of water, and allowed to run through. Gallid acid , catechin and epicatechin were eluted with 1.5 mL (3 h 0.5) of 30% methanol containing 50 gmL1 IS. The elute was collected and diluted to the mark with 30% methanol containing 50 gmL1 IS in a 2 mL flask. The resultant solution was at last filtered through a 0.45 m membrane filter before HPLC analysis