Fast Determination of Antioxidant Capacity of Food Samples Using Continuous Amperometric Detection on Polyester Screen-printed Graphitic Electrodes

The determination of antioxidant capacity of food samples using disposable polyester screen-printed graphitic macroelectrodes (SPGE) coupled with a batch-injection cell based on the measurement of the consumption of 2,2-diphenyl-1-picrylhydrazyl (DPPH.) is reported. The SPGEs are organic-resistant electrodes and thus compatible with food samples and organic solvents used to dissolve DPPH.. A micropipette controlled the release (193Ls(-1)) of sample (150L) upon the sensor/working electrode immersed in electrolyte (1:1 ethanol/methanol containing 0.05molL(-1) LiCl). The first demonstration of this protocol was devoted to the analysis of edible oils. The remaining DPPH. was amperometrically detected at +0.1V (vs. pseudo AgCl). The antioxidant capacity (percentage of DPPH. scavenging and mg equivalent of tocopherol) was obtained using the proposed and spectrophotometric methods. The results were in agreement according to t-test (confidence level of 95%). The method is precise (RSD=2.3%, n=12), fast (180h(-1)), presents low detection limit of DPPH. (1molL(-1)), and allows on-site analysis. Moreover, the proposed method can be extended to the analysis of antioxidant capacity of other samples of agricultural and food interests.