Analysis of pharmaceutical preparations containing catecholamines by micellar liquid chromatography with spectrophotometric detection

Abstract

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 C₁₈ 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.