Stepwise Injection Spectrophotometric Determination of Flavonoids in Medicinal Plants

A simple, rapid, and automated method for the spectrophotometric determination of flavonoids in medicinal plants was developed using a stepwise injection manifold. The determination was based on formation of colored complexes of flavonoids with Al(III) in micellar media. Analytical characteristics of the determination were significantly improved when cetylpyridinium chloride was used as a micellar catalyst. It was found that the rate of colored complex formation of rutin with Al(III) increased (k=(1.8 +/- 0.1)center dot 10(4)min(-1)mol(-2) L-2) in the presence of cetylpyridinium chloride. Under the optimum conditions, a linear response was found from 0.004 to 0.2% (volume of weight %). The detection limit (3s) was determined as 0.001% rutin versus the weight of the sample. The developed method was used for the analysis of different medicinal plants for flavonoids.