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ABSTRACT The response of the Ce(III)-catalyzed phloroglucinol (1,3,5-trihydroxybenzene)-based Belousov Zhabotinsky system to the addition of various antioxidants (ascorbic acid, glutathione, inosine, N-acetylcysteine) is monitored at 30°C under stirred batch conditions. This method is convenient and has good sensitivity for the determination of these antioxidants. The addition of these antioxidants to the BZ mixture influences the oscillatory parameter (number of oscillations) to an extent that depends on the concentration of the antioxidant. The experimental results have shown that the number of oscillations decrease on increasing the concentration of antioxidant. The calibration plots show a linear relationship ( R2 = 0.98 for ascorbic acid and glutathione and R2 = 0.99 for inosine and N-acetylcysteine) between the number of oscillations and the [antioxidant] over the concentration range of 0.0125-0.5, 0.05-0.2, 0.025-0.1, and 0.1-0.5 mol L−1 with detection limits 6.9 × 10−5, 2.762 × 10−4, 1.381 × 10−4, and 5.524 × 10−4 mol L−1 for ascorbic acid, glutathione, inosine, and N-acetylcysteine, respectively. Some aspects of the mechanism of these antioxidants on the BZ system have been discussed. [ABSTRACT FROM AUTHOR]