title: Determination of free DOPA and 3-O-methyl-DOPA in human plasma by high-performance liquid chromatography with electrochemical detection.
abstract: A procedure was devised for the determination of the unconjugated non-protein-bound fraction of 3,4-dihydroxyphenylalanine (DOPA) and 3-O-methyl-DOPA (3-OMD) in plasma using a reversed-phase liquid chromatographic system coupled with electrochemical detection. Sample preparation involves rapid isolation of the unbound drugs from the drug-protein complex by ultrafiltration through a membrane with a molecular weight cut-off of 10,000 dalton. One chromatographic run requires less than 10 min. The relative standard deviation is less than 3% for the within-assay imprecision and less than 4% for the between-assay imprecision. The detection limits for DOPA and 3-OMD are 0.2 and 1.3 ng/ml, respectively.
authors.affiliation: Laboratorio di Analisi Chimico-Cliniche e Neurochimica, IRCCS, Fondazione 'Istituto Neurologico C. Mondino', Università di Pavia, Italy.
authors.forename: G V
authors.initials: GV
authors.lastname: Melzi d'Eril
authors.forename: V
authors.initials: V
authors.lastname: Rizzo
mesh_terms: D004295:Dihydroxyphenylalanine / Q000097:blood*; D004563:Electrochemistry; D006801:Humans; D008750:Methyldopa / Q000097:blood*; D014462:Ultrafiltration
chemical_list: D008750:Methyldopa; D004295:Dihydroxyphenylalanine