ANALYSIS OF PHARMACEUTICAL PREPARATIONS CONTAINING CATECHOLAMINES BY MICELLAR LIQUID-CHROMATOGRAPHY WITH SPECTROPHOTOMETRIC DETECTION

An HPLC procedure for the determination of catecholamines (CAs) and other compounds which are associated with CAs in pharmaceutical preparations is described. A sodium dodecyl sulfate (SDS) micellar mobile phase, a C-18 column and spectrophotometric detection at 280 nm were used. A mobile phase containing 0.1 mol l(-1) SDS, 0.67 mol l(-1) (5% v/v) propanol and buffered with phosphate at pH 3 is recommended. The CAs gave limits of detection in the 4-7 ng ml(-1) range. The procedure was applied to the determination of L-dopa, 2-methyldopa, epinephrine, dopamine and isoproterenol, as well as other compounds frequently associated with CAs in pharmaceuticals including phenylephrine, carbidopa and hydrochlorothiazide. The solute-micelle association constants and the partition constants of the CAs between the stationary phase and water in several media, and the protonation constants of L-dopa and 2-methyldopa, were evaluated from chromatographic data.