Figure 1.

Differential pulse voltammograms for 0.1 mM solutions of (a) (black line) caffeic acid, (blue line) 5-bromocaffeic acid, (green line) 3,4,5-trihydroxycinnamic acid, and (red line) hydrocaffeic acid and (b) (black line) ferulic acid, (blue line) 5-bromoferulic acid, (green line) sinapic acid, and (red line) hydroferulic acid, in physiological pH 7.3 supporting electrolyte. Scan rate: 5 mV s⁻¹.