FLOW ANALYSIS-SPECTROPHOTOMETRIC DETERMINATION OF L-DOPA IN PHARMACEUTICAL FORMULATIONS BY REACTION WITH P-AMINOPHENOL

A new method has been developed for the spectrophotometric determination of L-dopa in pharmaceutical formulations. The method is based on the reaction between the open-chain quinone of L-dopa, obtained in NaOH, and the benzoqinoneimine form of p-aminophenol, in the presence of KIO4. The reaction product is determined at 574 nm by using both alternately procedures, one based on the stopped-flow and another on a how injection approach. Under the best experimental conditions L-dopa can be determined with a limit of detection of 52 ng/ml and a relative standard deviation of 0.2% for three replicate measurements of a solution containing 4 mu g/ml.