L-Tryptophan (Trp) and tryptamine (Trp-NH2) react with chloroacetaldehyde (CAA) to form derivatives with strong fluorescence (Ex=305 nm and Em=455 nm for Trp ; Ex=304 nm and Em=452 nm for Trp-NH2) in a dilute hydrochloric acid solution under optimal conditions. Other biogenic indolylethylamines and phenylethylamines do not form fluorescent derivatives with CAA.
