Simultaneous multiple electrode liquid chromatographic-electrochemical assay for catecholamines, indole-amines and...

To enhance the selectivity of liquid chromatographic-electrochemical assays for biogenic amines and metabolites in brain tissue, multiple electrode transducers were investigated. Two configurations of dual working electrodes were examined: parallel-adjacent and series arrangements. Using the raw detector currents with each configuration, peak-height ratios from simultaneously generated chromatograms were calculated to assess the selectivity of the instrument for direct injections of brain tissue supernatant. Ratios were consistent with injections of standards. Nearly coeluting peaks such as norepinephrine and 3-methoxy-4-hydroxyphenylglycol were resolved by using dual detector electrodes in series; only the catecholamines were detected at the downstream electrode owing to their electrochemical reversibility. The scheme was applicable to the assay of norepinephrine, 3,4-dihydroxyphenylacetic acid, dopamine, homovanillic acid, serotonin, 5-hydroxytryptophan and 5-hydroxyindole-3-acetic acid in brain tissue in less than 15 min.