Determination of dopamine, norepinephrine, and related trace amines by prechromatographic derivatization with naphthalene-2,3-dicarboxaldehyde

Dopamine, norepinephrine, octopamine, tyramine, and 3,4-dihydroxybenzylamine react readily with naphthalene-2,3-dicarboxaldehyde in the presence of cyanide ion under mild conditions to give highly fluorescent cyanobenz[f]isoindole (CBI) products. The CBI products exhibit good solution chemical stability. The high-fluorescence quantum efficiency of the CBI fluorophore and the ability to excite these adducts in the visible region (420-450 nm) enhance the sensitivity and selectivity of this derivatization detection technique. The CBI products of catecholamines and "trace" amines are readily separated by reverse-phase HPLC giving detection limits in the 20 to 60 fmol range (S/N = 3). A prechromatographic derivatization HPLC assay for the trace analysis of dopamine and norepinephrine in urine is described.