No abstract

A sequential injection analysis (SIA) with chemiluminescence (CL) detection was developed for the measurement of antioxidative activity against singlet oxygen ( 1 O2). Lactoperoxidase-hydrogen peroxide-bromide ion system was used for the generation of 1 O2. When a 100 mM sodium acetate buffer (pH 4.5) was used as a carrier solution, the SIA-CL system could be optimized with respect to the flow-rate of the carrier, concentration of reagents and their aspiration order. The antioxidative activity was expressed as an attenuation of luminol CL due to the quenching of 1 O2 by an antioxidant. The relative standard deviations of antioxidative activity (n = 3) against 1 O2 for within-and between-day analyses were ≤1.6% (20 µM Trolox). The system was successfully applied to the assay of antioxidative activities of various antioxidants including vitamin supplements at a rate of 10 samples within 15 min. The proposed SIA-CL system was rapid and reproducible with minimum consumption of the sample and of reagents, and thus was useful for the screening of compounds possessing antioxidative activity against 1 O2.

A method that combines sequential injection analysis (SIA), flow injection analysis and chemiluminescence (CL) detection was developed for the quasi-simultaneous determination of antioxidative activities against superoxide anion (O2-) and nitric oxide (NO). The antioxidative activity was expressed as the decrease in luminol CL intensity caused by the quenching of O2- or NO by an antioxidant. The SIA system consisted of two syringe pumps, two selection valves, two holding coils, an HPLC pump to deliver luminol solution, and a CL detector. Operation of the syringe pumps and multiport valves was controlled automatically using a personal computer with appropriate software. A hypoxanthine (HX)-xanthine oxidase (XOD) system was used for the generation of O2-, and (+/-)-(E)-4-methyl-2-[(E)-hydroxyimino]-5-nitro-6-methoxy-3-hexenamide (NOR1) was employed as NO donor agent. The repeatability of the method was evaluated with 35.2 microg ml(-1) L-ascorbic acid, and the relative standard deviations (RSD) of the antioxidative activities were less than 3.8%. The quasi-simultaneous determination of the antioxidative activities in one sample was completed within 2.0 min. The antioxidative activities of some antioxidants and commercially available supplements containing certain antioxidants were successfully determined using this system. The proposed system is rapid and reproducible, and thus may be useful for the screening of functional foods, supplements and pharmaceutical formulations that exhibit antioxidative activity.