This work proposes the application of batch-injection analysis with amperometric detection to determine
the antioxidant capacity of real samples based on the measurement of DPPH radical consumption. The
efficient concentration or EC50 value corresponds to the concentration of sample or standard required
to scavenge 50% DPPH radicals. For the accurate determination of EC50, samples were incubated with
DPPH radical for 1 h because many polyphenolic compounds typically found in plants and responsible
for the antioxidant activity exhibit slow kinetics. The BIA system with amperometric detection using a
glassy-carbon electrode presented high precision (RSD = 0.7%, n = 12), low detection limit (1 lmol L1)
and selective detection of DPPH (free of interferences from antioxidants). These contributed to low detection
limits for the antioxidant (0.015 and 0.19 lmol L1 for gallic acid and butylated hydroxytoluene,
respectively). Moreover, BIA methods show great promise for portable analysis because
battery-powered instrumentation (electronic micropipette and potentiostats) is commercially available.