Abstract
Homovanillic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA) were determined by direct injection of plasma, urine and cerebrospinal fluid (CSF) into a liquid chromatographic system comprising three columns, one packed with an anion-exchange gel and two with reversed-phase material. The acidic compounds were isolated by anion-exchange on the first column, enriched on the second and separated by reversed-phase chromatography on the last column. 5-HIAA and HVA were detected by coulometry and amperometry on two working electrodes coupled in series, giving limits of determination in plasma of 4 and 5 nmol l −1 respectively. Endogenous plasma, urine and CSF-levels were determined with a precision (RSD) of 2–4%. 3-Methoxy-4-hydroxyphenylpropionic acid was identified in normal plasma and urine.
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