Simultaneous determination of levodopa methyl ester, levodopa, 3-O-methyldopa and dopamine in plasma by high-performance liquid chromatography with electrochemical detection.
A new procedure is described for the simultaneous determination of levodopa methyl ester (LDME) and its biotransformation products levodopa (L-DOPA), 3-O-methyldopa (3-OMD) and dopamine (DA) in stabilized plasma samples, using reversed-phase high-performance liquid chromatography. A coulometric detector equipped with a dual-electrode system operating in the redox mode was used to simultaneously quantitate all compounds. This system generated a double signal monitored by a dual-channel acquisition data system and allowed quantitation of compounds at the nanogram level. The intra- and inter-assay precision varied in the 2.4-6.9% and 3.2-9.1% ranges respectively, whereas the recoveries were close to 85% for L-DOPA and 3-OMD and 70% for DA and LDME. Samples may be stored at -80 degrees C for 15 days before analysis. The method was applied to plasma samples after oral administration of LDME to rats, but it may also be suitable for human pharmacokinetic studies.
Rondelli
I
I
Chemical and Biopharmaceutical Research, Chiesi Farmaceutici S.p.A., Parma, Italy.
Acerbi
D
D
Mariotti
F
F
Ventura
P
P
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004298:Dopamine / Q000097:blood*; D004563:Electrochemistry; D006801:Humans; D007980:Levodopa / Q000031:analogs & derivatives* / Q000097:blood; D010084:Oxidation-Reduction; D051381:Rats; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000097:blood
D014443:Tyrosine; D007980:Levodopa; C035420:levodopa methyl ester; C008404:3-methoxytyrosine; D004298:Dopamine