Determination of fluorescent cyanobenz[f]isoindole derivatives of dopamine and norepinephrine using high performance liquid chromatography with chemiluminescence detection

Dopamine (DA), norepinephrine (NE) and 3,4-dihydroxybenzylamine (DHBA) are converted to highly fluorescent cyanobenz[f]isoindole (CBI) derivatives by reacting these amines with naphthalene-2,3-dicarboxaldehyde in the presence of cyanide ion. Femtomole amounts of these CBI derivatives separated by reverse-phase high performance liquid chromatography can be detected by a post-column chemiluminescence system utilizing bis(2,4-dinitrophenyl) oxalate and hydrogen peroxide. Linear detection response was observed between 1 to 600 fmol, giving a signal to noise ratio of approximately 15 at the 1 fmol level. An assay procedure was developed for the determination of DA and NE in 20 μL of urine sample using DHBA as the internal standard.