Objective: To probe into the speciality of NaNO2 - Al ( NO3) 3 - NaOH colorimetry for determination of total flavonoids. Method: Make a series of flavonoids and non - flavonoids react with NaNO2, Al (NO3)3, NaOH solution, then mensurate their absorption curves at the range of 400-700 nm. Result: At the wavelength 500 nm, some flavonoids showed no λmax or very weak absorption, and to the opposite, some non -flavonoids have maximized absorption or have upper absorption. Conclusion: It is not exclusive to dete...