Stock solutions were prepared by dissolving rutin (15.00 mg),quercetin (6.00 mg), and iso quercetin (2.00 mg) in methanol(50 mL), respectively. Then the solutions were diluted step by step with methanol to give six different concentrations of working standard solutions. The working standard solutions were analyzed by the established method in triplicate. Calibration curves were constructed by plotting the peak area (Y) versus the concentration of rutin, quercetin, and iso quercetin (X), respectively.