Multi-syringe flow injection system for the determination of the scavenging capacity of the diphenylpicrylhydrazyl radical in methanol and ethanolic media.

A multi-syringe flow injection system for the determination of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH^•) scavenging capacity using methanol or ethanolic solutions as reaction media is presented. A stopped flow approach was implemented in order to monitor the DPPH^• consumption using spectrophotometry at 517 nm. The kinetic profile for the first 3 min of reaction was determined for several antioxidant compounds and the number of DPPH^• molecules reduced by one molecule of antioxidant was calculated whenever the absorbance value was stable within the period of measurement. For ascorbic acid, trolox, isoeugenol and quercetin in methanol, the values obtained were similar to those reported in the literature. It was possible to perform 14 determinations per hour, consuming 0.34 µmol of DPPH^• per determination, which accounts for the application of this system as a screening tool for fast scavenger compounds. [ABSTRACT FROM AUTHOR]