[Rhodamine 6G association particle based spectrophotometric determination of hydroxy free radical and its application to the selection of antioxidant].

ABSTRACT

In HCl-NaAc buffer solution, the hydroxy free radical from the Fenton reaction is captured by excess KI and releases I3-. The I3- combines with Rhodamine B (RhB, lamdamax=554 nm), Rhodamine 6G(Rh6G, lamdamax=526 nm), Rhodamine S (RhS, lamdamax=526 nm), and butyl Rhodamine B(b -RhB, A,lamdamax56 nm) to form association particles, so the absorbance at max wavelength decreases. The concentration of hydroxy free radical (calculated by the concentration of hydrogen peroxide) is proportional to the decreased absorbance of the systems of RhB, Rh6G, RhS, b-RhB in the range of 0.136-0.680 microg x L(-1), 0.34-0.680 microg x mL(-1), 0.034-0.680 microg x mL(-1), 0.034-0.680 microg c mL(-1), espectively. Based on this fact, a new method for the determination of scavenging percentage of hydroxy free radical with antioxidant was developed. The resistance to oxidation of four substances and six kinds of tea extract were measured with satisfactory results.