Figure 4

(a) Cyclic voltammetry curves of 100.0 µM L-tryptophan on graphite electrode in Britton–Robinson buffer solution (pH 4.0) at different scan rates (from 25.0 to 150.0 mV/s); (b) Dependence of peak current of 100.0 µM L-tryptophan on the scan rate; (c) Dependence of logarithm of peak current of 100.0 µM L-tryptophan on logarithm of scan rate.