Abstract: A spinach - carbon paste electrode (prep. described; based on the cinnamic acid hydroxylase activity of spinach leaves) was used to determine cinnamic acid (I) and dopamine amperometrically at +0.9 V with reference and auxiliary electrodes of Ag - AgCl and Pt wire, respectively; 0.05 M phosphate buffer (pH 7.4) was used as electrolyte. Solution stirring (400 rpm) or flow (1.0 mL min-1) were used in batch- and flow injection experiments, respectively. A fast response to changes in concentration. of I were obtained. Flow injection rates of 135 samples h-1 and a detection limit of 0.2 mM I were achieved. The calibration graph showed linearity up to 4 mM and a coefficient of variation of 2.0% (n = 25). The method could be applied to determine I in the perfumes.