Simple Electrochemical Methods for Antioxidant Capacity Test

Two simple electrochemical methods for measuring antioxidant capacity were tested; cyclic voltammetry (CV) method based on redox activity of antioxidant and flow injection with amperometric detection (FI-AD) method based on scavenging ability of antioxidant toward 2,2'-azino-bis(3-ethylbenzothiazoline-6 sulfonic acid) (ABTS) radical and redox activity of the remaining ABTS reagent. The current signal from three electrode system using glassy carbon working electrode was monitored in phosphate buffer pH 7.0 medium. The classical spectrophotometric ABTS assay was included for comparison. Ginger infusion beverage was used as sample while gallic acid as standard antioxidant. Antioxidant capacity of ginger infusion was expressed as gallic acid equivalent (GAE) unit. Effect of infusion temperatures of 40-80 degrees C on antioxidant capacity was also determined. No significant difference between the GAE values determined from the same ABTS method but the GAE values from different methods were obviously different due to the basic principles. The FI-AD using laboratory made flow-through detector cell showed more advantages as no effect of electrode passivation during the analysis process and sample throughput was 28 h(-1) at the flow rate 1.5 ml/min.