Figure 5
(a) Differential pulse voltammogram of L-tryptophan in the concentration range from 5.0 to 150.0 µM on graphite electrode in Britton–Robinson buffer solution (pH 4.0), scan rate 50.0 mV/s (curves subjected to baseline correction); (b) The dependence of peak current on L-tryptophan concentration (investigated concentration range 5.0 µM–150.0 µM); (c) Differential pulse voltammogram of spiked L-tryptophan in milk sample on graphite electrode: (1) milk sample in Britton–Robinson buffer solution; (2) milk sample with added 40.0 µM of L-tryptophan; (3) milk sample with added 50.0 µM of L-tryptophan, and (4) milk sample with added 60.0 µM of L-tryptophan, scan rate 50 mV/s (curves subjected to baseline correction); (d) Differential pulse voltammogram of spiked L-tryptophan in apple juice sample on graphite electrode: (1) apple juice sample in Britton–Robinson buffer solution; (2) apple juice sample with added 40.0 µM of L-tryptophan; (3) apple juice sample with added 50.0 µM of L-tryptophan, and (4) apple juice sample with added 60.0 µM of L-tryptophan, scan rate 50 mV/s (curves subjected to baseline correction).
