Photometric Determination of Hydroxyl Free Radical Produced by Fenton Reaction Through Color-fading of Coomassie Brilliant Blue G250

In the dilute H2SO4 medium of ca.0.008 mol·L-1,the hydroxyl free radical,·OH,produced by the Fenton reaction reacted with Coomassie brilliant blue G250 (CBB G250),leading to color fading of the dye.Intensity of decrease of absorbance of CBB G250 measured at its absorption maximum of 582 nm (ΔA582) was found to keep linear relationship with the concentration of ·OH in the range within 25 mg·L-1.Based on the stoichiometric relationship between the reactant H2O2 and the product ·OH as shown by the Fenton reaction equation,the concentration of ·OH was expressed in terms of the concentration of H2O2.Precision of the color-fading reaction system was tested with standard solution of hydrogen peroxide for 6 replicate determinations,giving value of RSD (n=6) 0.6%.Based on these facts and on the results of its application to the determination of scavenging rate of several antioxidants against ·OH,this method was found to be feasible for the selection of anti-oxidants.