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.
Chemical and Biopharmaceutical Research, Chiesi Farmaceutici S.p.A., Parma, Italy.
I
I
Rondelli
D
D
Acerbi
F
F
Mariotti
P
P
Ventura
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