EFFECT OF CARBON IN-LINE FILTERS ON CATECHOLAMINE ANALYSIS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH COULOMETRIC ELECTROCHEMICAL DETECTION

Biogenic amines were analysed by high-performance liquid chromatograph y with electrochemical detection according to the method of Kilpatrick et al. [J. Neurochem., 46 (1986) 1865]. Equal amounts of structurally related catechols, i.e. noradrenaline (NA), dopamine (DA), dihydroxyb enzylamine (DHBA) and dihydroxyphenylacetic acid (DOPAC), produced ele ctrochemical signals of unequal sizes. Removal of the carbon in-line f ilter preceding the analytical electrochemical cell markedly increased the peak areas for NA, DA and DOPAC. For DA, this filter effect was l arge at pH 4.80 and gradually diminished at lower pH (4.60, 4.42, 4.20 ). These results indicate that the efficiency of electrochemical detec tion of catechols can be compromised by the use of carbon in-line filt ers.