•Batch-injection analysis (BIA) with amperometric detection of DPPH consumption.•Antioxidant capacity measurement (EC50 value) based on DPPH consumption.•BIA and spectrophotometry methods agree statistically for antioxidants.•BIA method provided comparable EC50 measurements to plant and tea samples. 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 1h 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 (1μmolL−1) and selective detection of DPPH (free of interferences from antioxidants). These contributed to low detection limits for the antioxidant (0.015 and 0.19μmolL−1 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.