Determination of free methyldopa in plasma by high-pressure liquid chromatography and electrochemical detection.

A quantitative method for the analysis of free methyldopa in plasma is described. The method is based on reversed-phase high-pressure liquid chromatography with electrochemical detection utilizing an ion-pairing agent. Separation of methyldopa from plasma is achieved by alumina adsorption. The parameters associated with the adsorption step are described. The lower limit of sensitivity is similar to or approximately 10 ng of methyldopa/ml with a corresponding retention time of 6.9 min.