Once the pump was switched on, the Co (II)-stream (7.12 × 10-4 mol/L, pH = 9.0 ± 0.03), luminolstream (2.28 × 10-4 mol/L, pH = 9.0 ± 0.03) and carrier-stream were initially mixed in order to reach a stable background. A stable baseline was obtained by mixing the H2O2-regent stream (0.8 × 10-3 mol/L, pH = 9.0 ± 0.03) into the system when cobalt (II) ion increased the chemiluminescene signal of luminol-H2O2 system. A loss of signal (negative peak) was observed which corresponded to the hydroxyl radical scavenging activity of the antioxidant when the antioxidant was injected to the system. Thus, the effect of antioxidant was measured by the depression of the signal from its initial level (uninhibited) and expressed as hydroxyl radical scavenging effect, calculated as follows: