Simple automated high-performance liquid chromatographic column-switching technique for the measurement of dopa and 3-O-methyldopa in plasma.
A reliable assay procedure for the determination of 3,4-dihydroxyphenyl-L-alanine (dopa) and its O-methylated metabolite 3-O-methyldopa (3-OMD) is described. Supernatants from deproteinized plasma samples were directly injected into a column-switching system, allowing on-line prepurification of the samples by cation-exchange chromatography followed by reversed-phase high-performance liquid chromatography with electrochemical detection. With this method, the detector response was linear from endogenous levels of dopa and 3-OMD up to microgram concentrations. This technique combines the simplicity of direct injection methods with advantages of procedures using a sample clean-up. It represents a valid tool for the rapid and accurate measurement of large numbers of plasma samples in animals treated with levodopa and in clinical trials with new levodopa formulations.
Zürcher
G
G
F. Hoffmann-La Roche Ltd., Pharmaceutical Research Department, Basel, Switzerland.
Da Prada
M
M
D000818:Animals; D001322:Autoanalysis; D001545:Benserazide / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D004295:Dihydroxyphenylalanine / Q000097:blood* / Q000493:pharmacokinetics; D004563:Electrochemistry; D006801:Humans; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D008297:Male; D051381:Rats; D013048:Specimen Handling; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics
D007202:Indicators and Reagents; D014443:Tyrosine; D004295:Dihydroxyphenylalanine; D001545:Benserazide; C008404:3-methoxytyrosine