Abstract
The present modification of the formaldehyde condensation method for demonstrating catecholamines and indolamines involves generation of the formaldehyde gas at + 80°C followed by reaction at +25 or 0°C. This procedure results in improved sensitivity for demonstrating noradrenaline and dopamine. Because adrenaline and peptides with NH2-terminal tryptophan give no or very weak fluorescence under these reaction conditions the modification also offers possibilities for improved discrimination between primary catecholamines on one hand and adrenaline and tryptophyl peptides on the other. Under the conditions used, the fluorescence yield of 5-hydroxytryptamine did not seem to be improved by variations in the reaction temperature.