AUTOMATED-DETERMINATION OF LEVODOPA AND CARBIDOPA IN PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ELECTROCHEMICAL DETECTION USING AN ONLINE FLOW-INJECTION ANALYSIS SAMPLE PRETREATMENT UNIT

An automated analytical procedure is described for the parallel determ ination of L-3,4-dihydroxyphenylalanine (levodopa, L-dopa, LD) and the analogous hydrazine compound carbidopa (CD) in dog plasma by ion-pair high-performance liquid chromatography with electrochemical detection (HPLC-ED). After deproteinization of the plasma samples with perchlor ic acid the catecholamines were extracted from the supernatant by adso rption on a small column filled with alumina. The extraction and redis solution were automatically performed in a flow injection analysis uni t (FIA) coupled to the HPLC system, The performance of the whole syste m was tested on dog plasma samples including specimens taken after ora l administration of the anti-Parkinsonism drug Duellin(R), which is a combination tablet of levodopa and carbidopa. (C) 1997 Elsevier Scienc e B.V.