Stability-indicating method for the determination of levodopa, levodopa—carbidopa and related impurities

A simple and sensitive high-performance liquid chromatography method was developed for the determination of levodopa and levodopa—carbidopa formulations. In the combined formulation, the method separates these drugs from their potential impurities. A C18 column with a 0.05 M acetate buffer as mobile phase was utilized for this separation. The components in the column effluent were monitored with a coulometric detector. The method is simple, precise, stability indicating and represents an improvement over the currently available methods of analysis. The method was utilized to investigate the stability of the analyte solution. Upon standing at room temperature, the analyte solution developed several peaks which correspond primarily to the degradation of 6-hydroxydopa.